Nicolas Rieucau

Gabriel Sabbagh

JEFFERSON'S UNKNOWN INFORMANT ON NECKER IN 1789: AN EPISODE OF DIPLOMATIC HISTORY INVOLVING CONDORCET

Keywords: Jefferson, Condorcet, Necker, Turgot, diplomatic history

The American envoy in Paris, Jefferson, sent on

INTRODUCTION

The main personae of this paper are Thomas Jefferson, Marie-Jean-Antoine-Nicolas de Caritat, marquis de Condorcet and Jacques Necker, three of the most important thinkers and authors of the last third of the eighteenth century. The text whose author is here identified in all likelihood is a report on Necker, written in French and sent with a letter by Jefferson to John Jay, the Secretary 4 theory and of which Condorcet gave a copy to Jefferson. 5 The friendship of Condorcet and Jefferson is confirmed by a number of facts and texts: Condorcet was present at the farewell dinner of Jefferson in Paris in September 1789, 6 Jefferson remained faithful to the memory of Condorcet and remembered him as late as in 1819, 7 and Condorcet thought of Jefferson in his last moments when he advised his daughter in his will to appeal to Jefferson's protection. 8 While the possible influence of Condorcet's Essai on Jefferson has been, rather inconclusively, discussed, 9 there is no doubt that Jefferson's important belief that the earth belongs in usufruct to the living was shared by Condorcet and was very possibly inspired by him. 10 In September 1786 Jefferson was, with Benjamin Franklin, John Jay and Robert Morris, one of the first recipients of Condorcet's Vie de M. Turgot, which was sent to him from the Netherlands by Charles-Guillaume-Frédéric Dumas who was in charge of (clandestinely) publishing there the book, 11 a book which could not be sold in France openly. Sending forbidden books to a diplomatic address was a safe way of avoiding their interception by the French customs and indeed a copy of the book is recorded in the catalogue of Jefferson's library. 12 Jefferson owned other books by Condorcet, in particular the one against slavery, 13 and it is well-known that Jefferson attempted to translate this text in English. Jefferson also owned Condorcet's famous Esquisse d'un tableau historique des progrès de l'esprit humain, posthumously published in 1795, where Condorcet 5 Cf. Urken (1991), 223-224. 6 Cf. Albertone (1997), 189. 7 Jefferson mentioned the 'genius' of Condorcet in a letter to Thomas Short (31 October 1819), in Jefferson, Political writings (1999), 313-316. 8 Testament (March 1794), in Condorcet (1847-1849), t. I, 624. 9 Cf. Urken (1991), 231. 10 Cf. Albertone (1997), 242. 11 Cf. the letter of Dumas to Franklin (27 September 1786), in The Papers of Benjamin Franklin (1786-1787), vol. 44, 332. 12 Cf. Thomas Jefferson 's Library (1989), 24. 13 Réflexions sur l'esclavage des nègres, probably the edition published in 1788, cf. Thomas Jefferson 's Library (1989), 56) and The papers of Thomas Jefferson (1958), vol. 14, 498. expressed his faith in the unlimited perfectibility of mankind. 14 While Jefferson owned an edition of Malthus's Essay on the principle of population, 15 originally written partly to refute this work of Condorcet, he was far more sympathetic to Condorcet's thesis; he wrote on 18 June 1799 to William G. Munford that he believed 'also with Condorcet, that [man's] mind is perfectible to a degree of which we cannot as yet form any conception '. 16 Jefferson shared Condorcet's opposition to John Adams's Defence of the Constitutions of Government of the United States of America, published in 1787-1788 -a matter to which we will go back -, and, like Condorcet, had strong and diverse scientific interests. Their correspondence shows equal frankness and cordiality in their agreements and disagreements. 17 M. Albertone has provided many details on how Jefferson disseminated the work of Condorcet and tried to translate part of it. She has also stressed the intellectual proximity of Condorcet and Jefferson on a great many topics, in particular their affinity for the opinions of the Physiocrats. 18 While in Paris Jefferson paid considerable attention to the French political scene where Necker played an important part. He was involved in intricate commercial negotiations with France, mentioned Necker regularly in his communications to Jay and made use of his knowledge of Necker's psychology. 19 Well before his mission to Paris, in 1782, Jefferson had ordered 14 Cf. Thomas Jefferson's Library (1989), 53. 15 Cf. Thomas Jefferson's Library (1989), 91. Jefferson owned a two volumes edition, published in 1806 or later. 16 Cf. The Papers of Thomas Jefferson (2004), vol. 31, 126-130. 17 Jefferson sent in August 1791 a well-known letter to Condorcet, in which he simultaneously criticized the way France had adopted the metric system (along the lines recommended by Condorcet) and praised the mathematical talent of a "negro", Benjamin Banneker, in a fashion which was certainly pleasing to Condorcet, cf. The papers of Thomas Jefferson (1986), vol. 22, 98-99. 18 Cf. Albertone (1997), 188-189. Jefferson owned a remarkable run of physiocratic books, including Quesnay's rare Physiocratie (1768-1767), cf. Thomas Jefferson's Library (1989), 90. It is likely that Franklin's and Jefferson's copies of this book were the first ones to reach the United States. The claim that "if there was any serious intellectual contact between Jefferson and [Condorcet], it has left no trace for the period during which Jefferson was in France", found in O' Brien (1996), 34, is obviously false. 19 The letter of Jefferson to Jay of 19 November 1788 is quite typical. Jefferson observed that "the most important was to disgust Mr Neckar [Jefferson wrote indifferently Neckar and Necker] as an economist against their new fishery, by letting him foresee it's expense" The papers of Thomas Jefferson (1958), vol. 14, 211-217. Necker's first bestseller, his Compte rendu, published in 1781. 20 This book and Necker's De l'administration des finances de la France, published in 1784, 21 had been enormously successful 22 and contributed to foster their author's reputation but did not disarm his critics.

The sympathy of Condorcet for the Physiocrats and, far more importantly, his friendship with Turgot -who was certainly not an orthodox physiocrat yet launched during his brief ministerial tenure (1774-1776) a large program of reforms inspired by their doctrine, notably on the freedom of the commerce of grains -which permeates many works of Condorcet and the report on Necker, explain his hostility towards Necker. Well before his political ambitions had become clear, Necker had sparred in 1769 with Morellet, a fellow traveller of the Physiocrats, in his very first writing which revealed his dislike of the "abstract" thinking of Morellet and of the "Économistes", all of whom were opposed to the monopoly of the Compagnie des Indes. 23 Necker's opposition to the Physiocrats strengthened over the years: in 1773 he eulogized Colbert, 24 for them a nefarious figure, 25 in a manifesto conceived to promote his empirical vision of the economy and his persona. We will explain later on in detail that Condorcet's hostility towards Necker dates from this text. 26 Necker's belief that the commerce of grains had to be regulated and the curious combination of his political ambitions and of his somewhat 'socialist' convictions, exotic for an eighteenth century banker but apparently sincere,27 led him to directly confront Turgot's policy in 1775 in his most cogent treatise,28 published right before the French "Flour War", of that same year. This treatise and Condorcet's erroneous conviction that these riots were 20 Cf. The letter of d'Oyré to Jefferson (10 June 1782), in The papers of Thomas Jefferson (1952), vol. 6, 191. 21 Jefferson owned these two books, cf. Thomas Jefferson's Library (1989), 82. 22 Perrot (1992), 144 mentions about 80 000 copies and 20 editions of this book. 23 Cf. Necker (1769), 5. 24 Cf. Necker (1773). 25 The Physiocrats attacked Colbert in many texts. The most violent one is Mirabeau (1774).

the result of a plot mounted by the opposition to Turgot and that Necker's book was part of it intensified Condorcet's dislike of Necker. He violently attacked Necker and his book in a series of pamphlets published in the mid 1770s 29 and in his correspondence and various manuscripts as we shall see. While later on a number of friends of Turgot like Morellet and Du Pont reconciled with Necker, Condorcet remained very hostile to him and faithful to Turgot. After Turgot's death, he wrote his Vie de M. Turgot, an idealized biography of his hero, that he arranged to be sent to Jefferson upon publication, as previously mentioned.

The publication of this work in 1786 was a key step in what we believe was a process aiming to bring a revival of Turgot: it was followed by a run of works of Turgot published in 1788, which got the explicit approval of the French censorship to which they had been simultaneously presented in mid 1788. 30 It surprisingly included Le Conciliateur, which was previously considered as a highly controversial manifesto in favor of religious tolerance and whose authorship by Turgot has been sometimes contested: 31 Malesherbes, an important figure, a friend of Turgot and Condorcet, had recommended the approval of the censorship, which supports the hypothesis of a careful planned concerted effort. This approval which links to works undoubtedly by Turgot a courageous defence of unorthodox religious beliefs, in line with the known opinions of Turgot and his friends, seems to us the best proof that Turgot had at least a hand in Le Conciliateur, if he did not write it entirely. 29 The following list is not necessarily exhaustive: Lettre d'un laboureur de Picardie (1775a), Lettres sur le commerce des grains (1775b), Monopole et monopoleur (1775c), Réflexions sur le commerce des bleds (1776). About these texts, which are all certainly by Condorcet, we refer to Burnand (2009), 34-45, and specially to Méricam-Bourdet (2019). 30 Cf. Registre des permissions tacites, 1784-1789, Paris, Bibliothèque Nationale de France, Site Richelieu, Ms. Fr. 21987, f. 102-104, dated from 4 June 1788. 31 Le Conciliateur, ou lettres d'un ecclésiastique à un magistrat sur les affaires présentes, republished in 1788 under the name of Turgot, with two other works obviously by him. The first 1754 edition appeared anonymously, clandestinely as far as we know. Schelle (1913-1923), vol. 1, 391-393, was unaware of the circumstances of the 1788 publications and did not include Le Conciliateur in his edition of Turgot.

This text had an introduction by the anonymous editor announcing that the king will regret to be deprived of the wise advice of the great Turgot. 32 These publications were followed by two texts of Turgot, one of which was funded by one of Condorcet's and Turgot's friends, the Duke of La Rochefoucauld. 33 They were issued in 1789 and 1790 by Froullé. 34 The latter was in this period Condorcet's main bookseller and had published the 1788 edition of his Réflexions sur l'esclavage des nègres; the verso of the title of the 1790 text advertised only the 1789 publication and three other books, all fully or partly by Condorcet, one of which included the first appearance of a famous memoir by Turgot. 35 Each of the texts of 1789 and 1790 texts had a short introduction which is probably by Condorcet: the first one defended the lawfulness of the interest of money in terms similar to what Condorcet had written in his biography of Turgot and the second one insisted on the concepts of "utilité", and "justice", both central to Condorcet. The fact that the Duke of La Rochefoucauld funded at least one of these publications strengthens the belief that Condorcet had a hand in them and actively participated in the late 1780s in the renewal of the influence of Turgot.

The great historian Peter Groenewegen has previously discussed these 1788-1790 publications of Turgot without being aware of the funding of one of them by the Duke de La Rochefoucauld and had "conjectured"-his term -that they originated from Condorcet, partly by making use of other arguments. He was particularly interested in one of the 1788 publications and, having been unaware of the 1788 approval by the censorship previously mentioned, suggested only that it was published 32 "il regrettera que la mort de ce grand homme le prive de ses sages conseils", Avis de l'éditeur. 33 This fact, previously unnoticed to the best of our knowledge, follows from La Rochefoucauld's own words, cf. The correspondence of Richard Price (1994), vol. 3, 289. 34 The first published one is Mémoires sur le prêt à intérêt, et sur le commerce des fers and the second one Mémoire qui contient les principes de l'administration politique sur la propriété des carrières et des mines. 35 Condorcet, Sur les fonctions des États-Généraux et des autres assemblées nationales (1789), Mazzei (and Condorcet and Turgot), Recherches historiques et politiques sur les États-Unis de l'Amérique septentrionale (1788), John Stevens (and others, including Condorcet), Examen du gouvernement d'Angleterre, comparé aux constitutions des États-Unis (1789). The Recherches historiques et politiques incorporated Turgot's memoir on colonies, written in 1776 for Vergennes.

"possibly after 1786". 36 What precedes appears to vindicate his conjectures about Condorcet's involvement and the date of publication. It confirms that Condorcet was bent on honoring Turgot's memory in the late 1780s and early 1790s, as he thought that Turgot's works remained a valuable source of inspiration, to put at the disposal of the public. Between 1788 and 1790 Condorcet referred at least three times to Turgot's ideas, paying tribute to him on each occasion and calling him in 1790 "a man of genius promoted to a high position and removed from it uniquely by his virtue". 37 It is therefore not surprising that Turgot is present in a report on Necker written eight years after his death.

In June 1789, Necker, in charge in France of the important portfolio of finances, was at the height of his power and popularity in a country which relied on him to find a painless solution to its financial quagmire. Jefferson sent to Jay on 17 June 1789 his observations on the very beginning of the French Revolution and found fit to include a report on Necker who seemed bound to become one of its main actors. He explicitly endorsed the report with the following comment: " [Necker] is important to be known. I send [the report] to you as drawn by a person of my acquaintance who knows him well. He is not indeed his friend, and allowance must therefore be made for the high colouring. But this being abated, the facts and ground work of the drawing are just". 38 It is Jefferson's interest in Necker's psychology which led him to ask for a report on Necker, entitled in the original French Caractere de Monsieur Neckar. Rather remarkably, Jefferson kept or destroyed the manuscript he received and sent a copy of it, written by himself, presumably to preserve the anonymity of his informant. We will attempt to explain why Jefferson hid the name of his informant. 36 Cf. [START_REF] Groenewegen | The Economics of A[END_REF]), xx-xxi and xxxii-xxxiii, n. 117. 37 Cf. Condorcet (1847-1849), t. IX, 127, for 1790, " un homme de génie, que sa vertu seule avait appelé à une grande place, et que sa vertu seule en avait précipité" ; t. VIII, 372-373, for 1788; t. XI, 466, again for 1790. 38 The papers of Thomas Jefferson (1958, vol. 15, 190).

THE AUTHORSHIP OF THE REPORT

We can now present our proof of Condorcet's likely authorship. It is divided in three parts.

The first part outlines the method of the proof and details briefly some tempting but unfruitful attempts to devise other proofs. The second part systematically compares various assertions of the report to the opinions of Condorcet on Necker expressed in texts indisputably written by him. It is an accumulative series of arguments, none of which is decisive in isolation, but whose conjunction seems to us reasonably convincing. The third part confirms our conclusion, namely that Condorcet is the likely author of the report, by showing that every detail of the report is consistent with his authorship of it and by eliminating other possible authors of it, precisely because none of them could have authored its entire text. We will consider in this part an interesting passage of the letter sent by Jefferson to Jay in conjunction with the report, which seems to provide an additional connection between Condorcet and Jefferson in June 1789. We will also provide in the third part our tentative explanation of the reason which led Jefferson to not identify the report's author. While this explanation is speculative, it has led us to briefly revisit a famous controversy which opposed John Adams and Condorcet and to call attention to an extraordinary and neglected statement written by Turgot, in a letter now lost, sent to Tucker.

THE METHODOLOGY OF THE PROOF

A few words on our methodology are useful. Our initial guess that Condorcet is the author of the report was based on similarities between it and various texts of his and on the fact that we were unable to trace anybody except Condorcet among the French acquaintances of Jefferson who could have written it.

Three avenues were open to us to establish that Condorcet authored the report. The easiest one would have involved the discovery of a 'smoking gun', say an early draft or a modification of the report, not properly identified so far, in the huge corpus of Condorcet's writings. This naturally led us to peruse the standard editions of Condorcet's works, notably the Arago edition, 39 and the Inventaire Condorcet. 40 This exploration only led us to identify through the Inventaire a correspondent of Condorcet, previously unknown, Henry Etienne de Roques Bouchard de Clausonnette; Condorcet sent him as early as in 1773, clearly when Necker had published his Éloge de Colbert, a letter now lost, to be discussed later on and on the contents of which we have valuable indications: the reply of de Clausonnette has been preserved. 41 The second avenue, appealing in theory, would have consisted in a formal analysis of the text and in a comparison with the works of Condorcet by statistical methods. This does not work for the simple reason that the report on Necker is too short. We thank Stephen M. Stigler for having confirmed to us that this method requires far longer texts and for having referred us to a review 42 which explains why we had to discard it.

The only course left was to directly compare the report with all the writings of Condorcet which dealt with Necker. Part of the correspondence of Condorcet and two texts were amply sufficient for our proof, namely:

1. Condorcet's correspondence with his friends Amélie Suard and Jean-Baptiste-Antoine Suard. 43 J.-B.-A. Suard was pensioned by Necker and the couple was very well disposed towards 39 Condorcet, OEuvres (1847-1849). 40 Its aim is to have a census of the writings of Condorcet which are dispersed in about 160 different locations, and it is of course incomplete, cf. https://www.inventaire-condorcet.com/Inventaire/Lieux_de_conservation. 41 Cf. https://www.inventaire-condorcet.com/Inventaire/Correspondance?ID=304. 42 Stigler (1983). 43 Correspondance inédite de Condorcet et Mme Suard, M. Suard et Garat (1771-1791). The extant correspondence gives only an imperfect idea of the hostility of Condorcet towards Necker: Mrs Suard destroyed several letters which were insulting for Necker ("J'ai déchiré presque toutes les lettres […] où le caractère de M. Necker était insulté", ibid., 164). The extracts published long ago by Doumic (1911 and 1912) are not adequate for our purpose. 12 him. Condorcet took pleasure in including in his letters many piques against Necker. Since repeated use of this correspondence will be made, we will denote it by A. The last lines of Mirabeau (1760, 336) promise that France will resurrect provided "Financiers" disappear. 47 Cf. 48 Terray was in charge of finances from 1769 to 1774. 49 We follow here the Pintard translation, as the other translation seems to us less appropriate. The aspects of the report which have been omitted in the above comparisons will be now covered.

ALL DETAILS FIT

In this section, we buttress the claim that the details of the report we failed to consider are consistent with Condorcet's authorship and that we can safely eliminate other possible contenders previously considered by the editors of The papers of Thomas Jefferson, and we provide a tentative explanation for why Jefferson decided to hide the name of the author of the report.

ABOUT CONDORCET, CALONNE, THE ÉLOGE DE COLBERT AND OTHER POSSIBLE AUTHORS OF THE REPORT

There are some interesting elements in the report and one intriguing component of the accompanying letter of Jefferson to Jay of 17 June 1789 that we failed to mention so far.

The report contains a few sentences about Calonne, who had with Necker a controversy about the latter's alleged responsibility for the financial state of France which does not really concern us.

The report claims that "M. de Calonnes has undertaken this investigation [of Necker's calculations], […] that he has already begun to unmask his antagonist, […] and that the memoires of M. de Calonnes, have greatly impaired [Necker's] reputation". This benevolence of the report's author towards Calonne is easy to explain. Calonne had tried to revive some of Turgot's ideas and it is not surprising that supporters of Turgot tended to favor Calonne in his dispute with Necker.

The main point here is that Condorcet was indebted to Calonne for personal reasons. 50 Condorcet occasionally expressed his gratitude towards Calonne: "I am interested by gratitude in M. de

Calonne" (je m'intéresse par gratitude à M. de Calonne). 51 The mentions of Calonne in the report, although not specially revealing, are perfectly consistent with our attribution of it to Condorcet.

Another passage of the report that was omitted is far more interesting. The report starts with a long paragraph relating Necker's departure from Geneva and his financial successes in Paris. To explain this we need to engage with Francalanza (2010) Necker and asserts that both men are "complicit " in this matter. 58 Quite remarkably, Turgot and Condorcet were united in 1773, well before Turgot was in charge of French finances, by their common opinion on Necker: Turgot is present in the hostility of Condorcet towards Necker before his ministerial tenure, when it started, in early September 1773, and this point was apparently overlooked. It is clear that the section of the report which relates the beginning of Necker's financial successes is perfectly consistent with the early interest of Condorcet in Necker and with his desire to know more of him as expressed to de Clausonnette, even if we have only the latter's reply. 54 Cf. Letter LXVII, A, 113, n. 2. 55 Cf. Correspondance inédite de Condorcet et de Turgot (1770-1779), letter XCVI, 130. 56 Cf. Francalanza (2010), 709. 57 "J'ai lu, Monsieur, les reflexions sur Colbert et je vous les renvoie." (Wilmington, Hagley Museum and Library, acc. 386). We are quoting here the original manuscript of this letter since the printed text (Correspondance inédite de Condorcet et de Turgot (1770-1779), letter XCVI, 130) is misleading and has replaced "les réflexions" by "vos réflexions". Schelle (1913-1923)

20

Although we discarded the statistical study of the text, we would like to dispel any possible doubt about one word which appears in a quite ordinary meaning in the report on Necker, the word 'probablement' (probably). Would a mathematician interested in the foundations of Probability Theory use the word in this fashion? Condorcet had written himself cogent remarks on the difference between the ordinary use (sens 'vulgaire') and the scientific use of the word 'probable'. 59 The matter is satisfactorily settled once one notes the numerous ordinary occurrences of the words 'probable' or 'probablement' in his works and even in 1789 or around this year. 60 It would be inappropriate to infer from the occurrence of 'probablement' in the report that its authorship by

Condorcet is unlikely (no pun intended).

Another superficially intriguing passage of the report is a relatively balanced sentence which granted that Necker was less harmful than his immediate predecessors: "necessity has recalled this man to the ministry: and it must be confessed, that he is beyond comparison a less mischievous minister than his predecessors". 61 One should note that, just six months before the report on Necker,

Condorcet had written two letters to Mrs Suard giving a far more restrained opinion on Necker than his usual fare: 62 it is likely that the hopeless situation at the beginning of the French revolution influenced Condorcet and that he took into account the official character of the report on Necker and its diplomatic weight. However the report's conclusion summarizes adequately the global 59 Cf. Arithmétique politique, 577. 60 Cf. Condorcet (1847-1849) While the position of Adams as stated in his 1787-1788 book was somewhat cautious, he was far more outspoken and did not spare Condorcet in his Discourses on Davila: "the friend of Turgot

[…] so great in geometry, is not more accurate in the science of government, than Etienne de la 70 The letter was first published in Price (1784) and in Mirabeau (1784), a fact omitted by Schelle (1913-1923), vol. 5, 532, who referred to later publications of it. It was certainly not intended for publication, contrary to what is asserted in Dippel (1997), 206, n. 9, and was published after the death of Turgot. 71 Cf. Tucker (1781, 92). The book, a European bestseller, was translated in French in 1782 and Necker (and Louis XVI) were certainly informed of the extract which presumably did not endear Turgot's memory to them. Its first publication in any language took place after Turgot's death, of course.

72 " I wish that the Americans be free, since they will be the First Example of a great People without neither Kings nor Nobles. " 73 It is e.g. unmentioned in the copious and unpublished thesis on Tucker, Ghorbal (2013).

Boetie, the friend of De Thou and Montaigne". 74 Adams had been elected vice-president of the United States in February 1789 and was recognized then as the most eminent American after Washington. He had been close to Jay who would certainly report to Washington the information provided by Jefferson. Jay's contempt for the French was well-known. Adams had mentioned it in his diary on 5 November 1782, upon his arrival in France. 75 Jefferson was certainly aware of the intimacy of Adams and Jay who had negotiated with Franklin, Vergennes and the British government the independence of the American colonies. He then had on almost any matter, including the constitutional controversy and Condorcet's ideas on the unlimited progress of mankind, views quite different from those of Adams. 76 He certainly did not share Jay's distaste of the French.

We suspect that ambassador Jefferson took great pains to copy the report in his hand for good reasons. His aim was certainly not to send an English translation: he copied himself the report in the original French without the assistance of an amanuensis or a secretary, most probably to insure total anonymity for its author. We believe that he kept the name of his informant secret, because this informant was Condorcet who had been involved in a controversy with Adams, now the vice president and a man with immediate access to the direct superior of Jefferson in the American diplomatic hierarchy, John Jay. One may note that the report was ignored in the French diplomatic circles, which would confirm that Jefferson's informant had no link with the French ministery of foreign affairs: we found no document in the Archives of this ministry which is connected to the report on Necker. Furthemore the report and Necker are absent from the book Bégaud, Belissa and 76 Adams was quite hostile to the " prophets of progress", as clear from his copious marginal annotations in the books of Condorcet he owned, cf. Haraszti (1952).

CONCLUSION

It is possible that some of the critical comments made about Necker in the report were voiced by other acquaintances of Jefferson, but we are not aware of any criticism of Necker which combines all the strictures of the report, each of which is found in some form in other texts of Condorcet. This, in a nutshell, is the main reason for our attribution of the report to Condorcet.

While it is quite likely that other interesting unknown texts by Condorcet will be identified in the future 77 , this report on Necker may well be his unique foray into diplomacy. To the best of our knowledge, it is the very last of the many recorded texts he wrote about Necker.

The report is undoubtedly an apt synthesis of the numerous pages written about Necker, and largely against him, by Condorcet throughout his career in politics and economics, with minimal concessions to its format. Condorcet grasped that he was sending an official, diplomatic, text to the ambassador of a friendly and important nation, which might influence its policy towards the government of France. Jefferson relied on Condorcet for this assessment of Necker and sent it very officially to the minister in charge of foreign affairs, John Jay, although he knew perfectly well that Condorcet was not the most objective informant: as he wrote to Jay, he was convinced that "the facts and ground work of the drawing are just".

Condorcet, but not Jefferson, seemed in June 1789 to have the premonition that Necker would lose his aura quite soon. Condorcet disliked the use made by Necker of public opinion but could not foresee how Necker would be forced to relinquish power in 1790.

77 New texts are added to the manuscripts section of the Inventaire Condorcet on a regular basis, cf. https://www.inventaire-condorcet.com/Inventaire/Manuscrit.

"

  2. A comment, again to be used repeatedly and from now on denoted by B, on Necker's De l'administration des finances de la France which was probably written immediately after the publication of this book, around the beginning of 1785. 44 3. A comment, again to be used repeatedly and from now on denoted by C, on a speech delivered by Necker on 5 May 1789 at the opening session of the États Généraux'. This text is especially interesting as it is strictly contemporary with the report on Necker received by Jefferson. 452.2 PROOF BY COMPARISONSThe report on Necker sent to Jefferson gathers a lot of the opinions about Necker voiced by Condorcet over the years. It summarizes Condorcet's critiques of Necker over the last fifteen years and includes a passionate defence of Turgot's policy. We will compare extracts of the report with A, B, C, and insert some comments. published for the first time in 1994 in Condorcet, Arithmétique politique (1767-1789), 379-384. 45 It was published also for the first time in Arithmétique politique (1767-1789), 680-682. 13 Les principes vrais et sages que Turgot voulait substituer aux abus de l'administration ayant été mal accueillis, il [Necker] saisit cette occasion de flatter l'ignorance et la malignité en publiant son ouvrage contre la liberté du commerce des grains" = "The wise and just principles by which Turgot aimed to correct the abuses of the administration, not having been received with favor, he [Necker] seized the occasion to flatter ignorance and malignity, by publishing his work against the freedom of the corn trade". This quotation refers to Necker (1775), a book intensely fought by Condorcet as previously seen, and points out to an author still immersed in the Turgot ministery, who remains convinced of the soundness of the freedom of the commerce of grains Necker's erroneous calculations The report haughtily dismisses the figures of Necker: "On s'est épargné la peine d'examiner ses faux calculs"= "we are spared the trouble of examining his false calculations". Criticism of Necker's religious convictions as publicized in his 1788 book An apparently innocuous and rather singular passage of the report deals with Necker's In B, one finds a long eulogy of Turgot, cf. Arithmétique politique, 382-383, with a mention of the "administration of this virtuous citizen" and of the "esteem of the nation" for him. The correspondence exchanged by

  Forbonnais (1758), t.1, 54 and 73, for the years 1603-1606. principles of economy, have nothing more than a false shew, and that the loans resorted to, in order to avoid the imposition of taxes, have been the source of the mischief which has reduced the finances to their present alarming condition". Necker's wealth acquired through the Abbé Terray: a thinly disguised attack on Necker's integrity Personal attacks against the way Necker acquired his wealth are found in the report, although few details are given. The report claims that "[Necker] owed much of his good fortune to his connections with the Abbé Terrai 48 […] in the short period of his ministry he had more than doubled his fortune. Not that he had plundered 49 the public treasury […] but […] being still connected with the house to which he addressed himself for much the greater part of his negotiations." politique compared on p. 680 the text of C to letters in A, were unaware of course of the report on Necker, and mentioned on p. 685 that during the Revolution Condorcet wrote hundreds of pages of detailed financial calculations, still unpublished and unclassified. Condorcet wrote to J.-B.-A. Suard in May 1775, letter CIII, A, p. 157, that "[Necker] has increased his wealth through the trade of our disreputed debt […] It is certain that he had the trust of abbé Terray" ([Necker] a augmenté sa fortune dans le discrédit de nos effets publics et par leur commerce […] Il est certain qu'il avait la confiance de l'abbé Terray".

  Necker's infatuation with himself As many politicians, Necker praised himself in his books. The report expresses exasperation about the matter: "he has been forgiven the nauseous panegyric which he has passed upon himself ". Similarly one finds in B, 379: "platitudes are the basis of a long praise of M. N. by himself Des lieux communs […] servent de fonds à un long panégyrique de M. N. fait par lui-même).

  Éloge de Colbert, at the end of August 1773,53 to undertake his own investigation of Necker. Before 50 When Necker took charge of French finances for the first time in June 1777, Condorcet refused to serve under him and resigned from his position of "Inspecteur des monnaies"; Condorcet had announced his intention to Maurepas in October 1776, cf. OEuvres deCondorcet (1847-1849), t. I, 297-298. Condorcet was reinstated by Calonne when the latter headed the ministry in November 1783.51 Cf. Letter CLXX (misnumbered CLXIX) of December 1785 to Mrs Suard, A, 227. 52 M. Necker is not a merchant, but a financier.53 The Éloge de Colbert received the éloquence prize of the Académie française on 25 August 1773; a review of it, dated 28 August 1773, pointed out byFrancalanza (2010), 699, n.1, was published byFréron (1773), t. 4, 289-312. Francalanza, É. Badinter had noticed in 1988 that Condorcet expressed, for the first time according to her, his hostility towards Necker in a letter sent to Mrs Suard at the latest in the beginning of September 1773. 54 Another letter of Condorcet, to Turgot, confirms that on September 8 1773 he had read the Éloge de Colbert and had a poor opinion of it. 55 Although this letter was previously quoted in relation with Condorcet's early interest in Necker, 56 the following point remained apparently unnoticed: the letter opens with a mention of a text on Colbert which Condorcet is returning to Turgot, and, more importantly, confirms that before 8 September 1773 Turgot himself was acquainted with Necker's book. 57 Several letters exchanged from September to December 1773 between Condorcet and Turgot abundantly prove that both men disliked Necker and his Éloge de Colbert, and are aptly summarized by Turgot when he promises to not betray Condorcet on

. In this paper Francalanza convincingly attributed to Condorcet an anonymous reply to Necker's Éloge de Colbert and made use of the only known letter sent by de Clausonnette to Condorcet, without having identified its author. This letter, referred supra, n. 41, was sent on October 12 1773 and was a reply to a letter from Condorcet, now lost, sent on September 30 1773. The de Clausonnette letter clearly answers a request by Condorcet to have information on Necker and apparently corrects an error of his: "Mr. Necker n'est point un négociant, mais un financier". 52 The rest of the letter stresses the common points of Colbert and Necker. It seems clear from this letter than Condorcet decided upon the publication of Necker's

  , vol. 3, Letters CXXV and CXXVI from Turgot to Du Pont, sent in September or October 1773, 627-628, guarantee that Turgot has read then Necker's book which gave to Turgot a very poor impression ["bien mauvaise idée"] of its author and allows to conjecture with almost total certitude that Turgot communicated to Condorcet a text on Colbert by Du Pont.58 Cf. Correspondance inéditede Condorcet et de Turgot (1770-1779, letters XCVIII, 132; CIII, 139; CV, 141 and CXIII, 156 where Turgot's quotation ["Je ne vous trahirai pas sur M. Necker. Nous sommes complices sur ce point"] is found.

  , t. IX, 29, for 1787; t. VIII, 393, for 1788; t. IX, 424, for 1789; t. XI, 369, for 1790. There are many other similar occurrences in this edition, too numerous to mention. We thank a reader of this paper for having asked us to clarify the uses of 'probable' and 'probablement' byCondorcet. 61 The context makes clear that Necker is not here compared to Turgot who was in charge from 1774 to 1776 (and was eulogized in the report), before the first tenure of Necker from June 1777 to May 1781, nor to Calonne who left the ministry of finances in April 1787, but to the rather insignificant Pierre-Charles de Villedeuil and Claude Guillaume Lambert, who were in charge from May 1787 to August 1788, right before the second tenure of Necker.62 Cf. Letter CLXXXI, A, 243, November 1788, "son discours imprimé [cf. son texte lu à la séance plénière d'ouverture de l'Assemblée des notables, le 6 novembre 1788] m'a paru raisonnable, ainsi que la manière dont il [les notables] les conseille" (his address in printed form [cf. his speech to the 'Assemblée des notables'] seemed to me reasonable, as his advice). Condorcet's next letter, to Mrs Suard, CLXXXII, A, 244, 28 December 1788, confirms Condorcet's relative objectivity then towards Necker: Condorcet does not exclude that Necker will take the right decision ("prendre un bon parti") about the voting procedure of the États Généraux. negative appraisal of Necker: "The ambitious desire he has always manifested of getting again into the administration, his work on the importance of religious opinions, and the memoires de M. de Calonnes, have greatly impaired his reputation".It is desirable to consider the likeliest authors of the report suggested by the editors of the Papers of Thomas Jefferson, Étienne Clavière and Pierre-Samuel Du Pont de Nemours. Clavière who lived in Geneva until 1782, undoubtedly was perfectly informed on the career of Necker. Yet two reasons allow to immediately eliminate his name: the first one is that his position towards the ideas and policy of Turgot was very nuanced, as lucidly shown in Whatmore and Livesey(2000), and was incompatible with the unreserved praise of Turgot displayed in the report. The second one applies to all the Genevans of whom one may think: Clavière, himself a financier who enriched himself very quickly in Paris in the 1780s, did not have for bankers and speculators the contempt of the report and felt that his knowledge of finances qualified him to enter politics. He certainly would not have distinguished a banker from a statesman as vigorously as the report did.The name of Du Pont de Nemours can be discarded immediately: 63 contrary to Condorcet who was hostile to religion and had anti-clerical feelings,64 Du Pont was a deist and expressed his empathy for all the religions which preach faith in one God.65 He never mocked and could never have mocked Necker's religious convictions, not to mention that Du Pont reconciled with Necker after Turgot's death and was employed by him. The letter of 17 June 1789 by Jefferson to Jay contained interesting data about Santo Domingo and the desire of its colonists to send representatives to the États Généraux. Jefferson It was largely initiated by a famous letter of Turgot sent to Price on 22 March 1778, which became widely known in 1784: 70 the title of the book by Adams (1787-1788) which was at the centre of the fight alluded to it. The controversy raged well after Turgot's death, in the late 1780s, and this Turgot letter played an important part in it. We have come across another document stemming from Turgot which was presumably known to Condorcet, and at least partly to Jefferson, Adams and Necker, but which has been forgotten by the commentators and editors of Turgot and in all the discussions of this controversy known to us. Turgot's letter to Price of 22 March 1778 had been preceded by an apparently similar letter, sent in February 1777, to Josiah Tucker, the famous economist and bishop. While this letter appears to be presently lost, Tucker published a revealing extract from it (in the original French) in 1781 in a book written in English and dedicated to no less than Necker: 71 "Je fais des Voeux pour la Liberté des Américains, parce que ce sera le Premier Exemple d'un grand Peuple, qui n'ait ni Rois, ni Noblesse." 72 This statement, nowadays mysteriously forgotten, 73 announces the 22 March 1778 letter to Price and is probably the most adequate short summary of the position of Condorcet and Jefferson, which was strongly opposed by Adams: Adams believed in the value of a natural aristocracy in preserving balanced government and, like Tucker, could not accept this statement of Turgot.

	63 We frankly find a bit too involved the way Harris (1986), 446 reached this result.
	64 Cf. Condorcet's Almanach anti-superstitieux (1773-1774).
	65 Cf. Du Pont (1808).

  74Adams (1805), 107. The Discourses on Davila appeared in The Gazette of the United States in 1790-1791 and were published in book form in 1805. Huggins (1997), 217, is mistaken in writing that these Discourses were published in 1788 and we do not believe, contrary to her, that Adams recognized in this text Condorcet's "talent". 75 " Mr. Jay says the French are not a moral people; they not know what it is; he don't like any Frenchman.", cf.Adams (1851), vol. III, 303.

This was essentially shown by[START_REF] Francalanza | Un inédit de Condorcet en réponse à l'Éloge de Colbert par Necker[END_REF].

For Necker's social ideas, cf. Lichtenberger (1895),[START_REF] Grange | Les idées de Necker[END_REF] Kaplan (2019).

Sur la législation et le commerce des grains (1775).

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The whole episode, a neglected piece of the diplomatic history of France and the United States, confirms the importance of the friendship of Jefferson and Condorcet and Jefferson's wide knowledge of the French political scene. He was clearly a consummate diplomatic envoy. One wonders whether the State Department had in its long history many informants of the caliber of Condorcet. Haraszti, Zoltan (1952), John Adams and the prophets of progress, Cambridge (Mass.): Harvard University Harris, Robert D. (1986), Necker and the Revolution of 1789, Lanham, Md; New York; London: University press of America. Huggins, Dorette (1997), "John Adams et ses réflexions sur Condorcet", in Anne-Marie Chouillet and Pierre Crépel (dir.), Condorcet. Homme des lumières et de la Révolution, Fontenay/Saint-Cloud: ENS Éditions, 207-221. Inventaire Condorcet : www.inventaire-condorcet.com. Jefferson, Thomas (1999), Political writings, Joyce Appleby and Terence Ball (ed.), Cambridge (UK): Cambridge University press. Jurt, Joseph (1992), "Condorcet et les colonies", Proceedings of the Meeting of the French Colonial Historical Society, 15, 9-21. Kaplan, Steven L. (1976), Bread, politics and political economy in the reign of Louis XV, The Hague: Nijhoff. Turgot, Anne Robert Jacques (1789), Mémoires sur le prêt à intérêt et sur le commerce des fers, Paris: Froullé. -(1790), Mémoire qui contient les principes de l'administration politique sur la propriété des carrières et des mines, et sur les règles de leur exploitation, Paris: Froullé Urken, Arnold B. (1991), "The Condorcet-Jefferson connection and the origins of social choice theory", Public Choice, 72 (2-3), 213-236.

Whatmore, Richard and Livesey, James (2000), "Etienne Clavière, Jacques-Pierre Brissot et les fondations intellectuelles de la politique des girondins", Annales historiques de la Révolution, 321,

des États-Unis, Londres et Paris: Froullé.

Stigler, Stephen M. (1983), "Review of Authorship puzzles in the history of Economics: a statistical approach", The Journal of Economic History, 43, 547-550.

The correspondence of Richard

Price, vol. III: February 1786-February 1791, W. Bernhard Peach (ed.), Durham, North Carolina: Duke university press; Cardiff: University of Wales press, 1994. The Papers of Benjamin Franklin (1786-1787), vol. 44: https://franklinpapers.org/framedVolumes.jsp?vol=44. The Papers of Thomas Jefferson (1950-), Julian P. Boyd [et alii] (ed), Princeton: Princeton University Press, 44 vols published. Thomas Jefferson's Library. A catalogue with the entries in his own order (1989), James Gilreath and Douglas L. Knox (ed.), Washington: Library of Congress. Tillet, Edouard (2001), La constitution anglaise, un modèle politique et institutionnel dans la France des Lumières, Aix-en-Provence: Presses universitaires d'Aix-Marseille. Tucker, Josiah (1781), Cui Bono? Or, An inquiry, what benefits can arise either to the English, or the Americans, the French, Spaniards, or Dutch, from the greatest victories, or successes, in the present war? Being a series of letters, addressed to Monsieur Necker, late Controller General of the finances of France, Glocester: printed by R. Raikes. -(1782) Cui Bono? Ou examen des avantages que les plus grandes victoires, ou les succès les plus complets, dans la guerre actuelle, pourroient procurer aux Anglois ou aux Américains; aux François, aux Espagnols ou aux Hollandois: en forme de lettres à Monsieur Necker, cidevant Directeur-Général des finances de France, Rotterdam: Bennett et Hake.

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Nicolas Guillet

Clément Primot

Vincent Maigron

Florence Degret

Pierre-Xavier Thivel

In-operando techniques for battery monitoring and safety issues prevention

teaching and research institutions in France or abroad, or from public or private research centers.

In-operando techniques for battery monitoring and safety issues prevention

Nicolas Guillet a,b,* , Clément Primot a,b , Vincent Maigron a,b,c , Florence Degret a,b,c and Pierre-Xavier Thivel c a) Univ. Grenoble Alpes, INES, F-73375 Le Bourget du Lac, France b) CEA, Liten, F-38054 Grenoble, France (http://liten.cea.fr/cea-tech/liten/en/) c) Univ. Grenoble Alpes, CNRS, LEPMI, F-38000 Grenoble, France (http://lepmi.grenoble-inp.fr/) * nicolas.guillet@cea.fr

Emission of transient acoustic waves Piezoelectric sensors

Example of an array of 6 PVDF screen-printed piezoelectric sensors on a 18650 battery type (CEA-Liten)

Possible origins of transient acoustic waves ? Dilatation of materials during lithiation-delithiation High mechanical constrains during thermal runaway

Ultrasound characterization

non-destructive test (NDT) method used to study the propagation of acoustic waves throughout the battery's materials

Acoustic waves of a defined wavelength are injected from a transducer within a material to detect absorptive or reflective defects such as fatigue cracks. According to their interaction with the materials, some wavelengths may be absorbed or reflected and/or transmitted. From this analysis, one can determine the existence of discontinuities within the sensed materials that prefigures the existence of cracks, defaults, bubbles etc…

A

  specific case: abnormal heat release during charge  Commercial 18650-type battery  Abnormal and unreliable heat release noticed on aged batteries (~85 % SoH) Normal thermal behavior (max .150 mW realeased)  Abnormal thermal behavior (max. 650 mW realeased)  Detection and quantification of the unexpected heat release events (2.1 fJ / AE event)  Abnormal AE events (44 fJ / AE event)  high energy acoustic events early detected during heat release  Specific signal noticed during abnormal thermal behavior  Significant change in material's sound wave transportation properties Three different monitoring techniques Rhodes, K.J. "Acoustic emission and X-ray diffraction techniques for the in-situ study of electrochemical energy storage materials" PhD diss. Univ. of Tennesse, 2011. http://trace.tennessee.edu/utk_graddiss/1119 Thermal analysis Thermal flux sensors principle, thermal flux sensor (Captec http://www.captecenterprise.com/) wrapped around a 18650-type battery. Example of cell voltage and heat flow measured on a 18650 battery during charge (CC at C/2 and CV) and discharge (C/2).  Direct measurement of the heat flow exchanged with surrounding  Thermal monitoring and management  Easy way to measure the Cp of the battery  Characterization  Thermal modelling Acoustic emission non-destructive test (NDT) method used to detect elastic transient acoustic waves produced by materials Relaxation of mechanical stresses in materials and at interfaces (e.g. due to volume change associated with lithium intercalation, cracks in the passivation layer of the electrodes, gas evolution during electrolyte degradation, etc…) emit transient elastic waves. They propagate throughout the battery materials to the surface and are recorded by sensors.

  obtained using UsC technique. left evolution of the cell voltage versus time during two successive cycles charge-discharge at C/2.6 and 25 °C. Colored dots superimposed on cell voltage correspond to each UsC measurement. Coloration is related to the variation of the physical properties of the acoustic signal detected. Right: representation of the cell voltage vs. capacity for the same data.  Three different in-operando and non intrusive techniques for battery monitoring and prevention of safety issues

Acknowledgements

The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under the Grant Agreement No. 608575, project Hi-C "Understanding interfaces in rechargeable batteries and super-capacitors through in situ methods" (01-09-2013 -28-02-2017). Project website: www.hi-c.eu Additionally, we gratefully acknowledge the French Rhône-Alpes Energy Cluster Tenerrdis and the French Fonds Unique Interministériel (FUI) for financial support of project OPERA2 (01-09-2013 -28-02-2017). David S. Eastwood et al. "Lithiation-Induced Dilation Mapping in a Lithium-Ion Battery Electrode by 3D X-Ray Microscopy and Digital Volume Correlation" Adv. Energy Mater. 2014, 4, 1300506


H Fleurbaey

R Grilli

D Mondelain

Alain Campargue
email: alain.campargue@univ-grenoble-alpes.fr

Measurements of the water vapor continuum absorption by OFCEAS at 3.50 µm and 2.32 µm

Keywords: Water vapor, continuum absorption, MT_CKD model, OFCEAS, transparency window, atmosphere

Measurements of the water vapor absorption cross-sections at two spectral points of the 2.1 µm and 4.0 µm transparency windows are performed by optical feedback cavity enhanced absorption spectroscopy (OFCEAS).

The self-continuum cross-section, CS, is measured for temperature values of 30 and 47 °C (303 and 320 K) at the 2853 cm -1 spectral point, corresponding to the lowest opacity region of the 4.0 µm transparency window. The CS values derived from the pressure squared dependence of the selfcontinuum, are found consistent with previous CEAS measurements in the considered window but significantly smaller than measurements by Fourier transform spectroscopy (FTS). The CS temperature dependence is discussed in relation with FTS measurements at high temperature.

Foreign-continuum cross-sections, CF, are newly obtained from OFCEAS spectra of moist air in flow regime at the 4302 cm -1 spectral point of the low energy edge of the 2.1 µm window. After subtraction of the monomer and self-continuum contributions, CF values are derived from the linear variation of the foreign-continuum absorption with the product of the water vapor and air partial pressure. The measurements were performed for temperature values of 34 and 47 °C (307 and 320 K) and no significant temperature variation is evidenced. The present CF value at 4302 cm -1 is gathered with previous CEAS measurements at seven spectral points of the 2.1 µm window. This consistent set of CF values is used to derive from a polynomial fit, the empirical frequency dependence of CF() over the 4250-5000 cm -1 range. Overall, the semi-empirical MT_CKD_3.5 values of CF are significantly underestimated in the centre of the considered window.

Introduction

Water vapor is the first greenhouse gas of our atmosphere. Its absorption represents between 50 and 70 % of the incoming solar light. The absorption spectrum of water vapor consists of narrow absorption lines due to transition between ro-vibrational levels of the water molecule and a more featureless continuum whose interpretation remains a major controversy in molecular spectroscopy [START_REF] Shine | The water vapor continuum in near-infrared windows -Current understanding and prospects for its inclusion in spectroscopic databases[END_REF]. The water spectrum is organized in bands of strong absorption, interspersed with a number of more transparent "windows". Although its amplitude is smaller in the windows, the relative importance of the continuum is much higher than in the band regions where the line absorption generally dominates.

The insufficient knowledge of the water continuum in the near infrared transparency windows makes it an important source of uncertainty for the radiative budget of the Earth's atmosphere. As a result of the lack of accurate experimental data, the semi-empirical MT_CKD model [START_REF] Clough | Line shape and the water vapor continuum[END_REF][START_REF] Mlawer | Development and recent evaluation of the MT_CKD model of continuum absorption[END_REF][4] is generally implemented in atmospheric radiative transfer codes. This model uses an empirical line shape modeling with sub-Lorentzian far wings and a weak interaction term between a water vapor molecule and another molecule for the intermediate wings. The parameters of this profile are then fitted to few laboratory or field measurements available mostly in the mid infrared.

Indeed, the quantitative determination of weak absorption continua is generally challenging by transmission spectroscopy (like Fourier transform spectroscopy (FTS)) as the continuum shows up as a small decrease of the transmitted spectrum baseline. The challenge is made even more difficult in the case of water vapor because of possible surface effects on the optics of the experimental setup. During the last decade, large experimental efforts have been performed to complete the pioneer works of Burch [START_REF] Burch | Continuum absorption by H2O[END_REF][START_REF] Burch | Continuum absorption by H2O in the 700 -1200 cm -1 and[END_REF][START_REF] Burch | Absorption by H2O in narrow windows between 3000 and 4200 cm -1[END_REF] in the transparency windows. FTS allowed for large spectral coverage [START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF][START_REF] Ptashnik | Near-infrared water vapor self-continuum at close to room temperature[END_REF][START_REF] Ptashnik | Water vapor continuum absorption in near-IR atmospheric windows[END_REF] and provided selfcontinuum cross-sections significantly higher than the generally adopted MT_CKD values in the 4.0, 2.1 and 1.6 µm windows. These FTS measurements were not confirmed by our recent series of experiments using cavity enhanced absorption spectroscopy (CEAS) [START_REF] Mondelain | The water vapor self-continuum by CRDS at room temperature in the 1.6 μm transparency window[END_REF][START_REF] Mondelain | Temperature de-pendence of the water vapor self-continuum by cavity ring-down spectroscopy in the 1.6 μm transparency window[END_REF][START_REF] Campargue | Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model[END_REF][START_REF] Richard | Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows[END_REF][START_REF] Lechevallier | The water vapor self-continuum absorption in the infrared atmospheric windows: new laser measurements near 3.3 and 2.0 μm[END_REF][START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF][START_REF] Vasilchenko | The water vapor self-and foreigncontinua in the 1.6 μm and 2.3 μm windows by CRDS at room temperature[END_REF][START_REF] Ventrillard | Accurate measurements and temperature dependence of the water vapor self-continuum absorption in the 2.1 μm atmospheric window[END_REF], namely cavity ring down spectroscopy (CRDS) and optical feedback-cavity enhanced absorption spectroscopy (OF-CEAS).

These CEAS measurements, supported by a clear pressure squared dependence of the continuum absorption, have been recently used to constrain the MT_CKD self-continuum in the 4.0, 2.1, 1.6 and 1.25 µm windows.

In the case of the foreign-continuum arising from interactions between water molecules and molecular oxygen and nitrogen, experimental data are even more scarce in particular at room temperature [START_REF] Hartmann | Recent advances in collisional effects on spectra of molecular gases and their practical consequences[END_REF].

Regarding the transparency windows, cross-sections provided by FTS [START_REF] Baranov | The continuum absorption in H2O+N2 mixtures in the 2000-3250 cm -1 spectral region at temperatures from 326 to 363 K[END_REF][START_REF] Baranov | H2O-N2 collisioninduced absorption band intensity in the region of the N2 fundamental: ab initio investigation of its temperature dependence and comparison with laboratory data[END_REF][START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF] in the mid-IR windows and by cavity ring down spectroscopy (CRDS) in the 2.1 µm window [START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF] have led to a significant increase of the MT_CKD foreign-continuum since the 2.8 version [START_REF] Mlawer | Development and recent evaluation of the MT_CKD model of continuum absorption[END_REF].

The temperature dependence of the self-and foreign-continua is of importance for atmospheric applications. The self-continuum is known to have a strong negative dependence around room temperature while the foreign-continuum is believed to be much less sensitive to the temperature. Note that the temperature dependence may help to discriminate different processes responsible of the continuum: far wings of the rovibrational lines, "water dimers"and other bimolecular complexes, such as O2-H2O and N2-H2O, and collision-induced absorption (CIA).

The present work is a further step in our experimental investigation of the water self-and foreigncontinua by CEAS. While the FTS technique allowed for wide spectral coverage, laser based techniques are inherently more sensitive but generally limited to narrow spectral intervals depending of the availability of laser sources. Here, we report on new OFCEAS self-continuum cross-section, CS, at 30

and 47 °C at the 2853 cm -1 spectral point in the center of the 4.0 µm transparency window and foreigncontinuum cross-sections, CF, at the 4302 cm -1 spectral point of the low energy edge of the 2.1 µm window at 34 and 47 °C. In the following part 2, we will present the experimental procedure and data acquisition adopted for the two series of measurements. [START_REF] Campargue | Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model[END_REF]. The (smaller) error bars given in Table 2 of Ref. [START_REF] Campargue | Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model[END_REF] are limited to the fit uncertainty b Total uncertainty of 30% [START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF]. The (smaller) error bars given in Table 2 of Ref. [START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF] are limited to the fit uncertainty. 2.

Experimental setup a.

OF-CEAS spectrometers

OFCEAS is a high-sensitivity technique which relies on optical feedback to efficiently inject the probe laser into a high-finesse V-shaped cavity [START_REF] Morville | Two schemes for trace detection using cavity ringdown spectroscopy[END_REF][START_REF] Romanini | Optical-feedback cavity-enhanced absorption: a compact spectrometer for real-time measurement of atmospheric methane[END_REF]. This technique has been used to measure water continua in other spectral regions [START_REF] Campargue | Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model[END_REF][START_REF] Richard | Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows[END_REF][START_REF] Lechevallier | The water vapor self-continuum absorption in the infrared atmospheric windows: new laser measurements near 3.3 and 2.0 μm[END_REF][START_REF] Ventrillard | Accurate measurements and temperature dependence of the water vapor self-continuum absorption in the 2.1 μm atmospheric window[END_REF]. The reader is referred to [START_REF] Ventrillard | Accurate measurements and temperature dependence of the water vapor self-continuum absorption in the 2.1 μm atmospheric window[END_REF] for a more detailed description. The use of a V-shaped cavity allows reinjecting part of the resonant intra-cavity field into the diode laser source. This optical feedback leads to laser emission width narrowing and a temporary locking of the laser frequency to the cavity mode, improving the efficiency of the cavity injection. Due to the fixed geometry of the cavity, the spectra have an intrinsically linear frequency scale with point spacing equal to the free spectral range (FSR). Both arms of the cavity have a nominally 40 cm length, corresponding to an FSR of 187.5 MHz. Applying a ramp on the diode laser current while keeping its temperature constant, spectra can be recorded over more than 100 cavity modes (~0.6 cm -1 ) at a rate of about 5 Hz. Transmission spectra are obtained by dividing the maximum output of the cavity at each mode by a reference photodiode signal, while a single ring down event is recorded at the end of each scan to retrieve the absolute absorption coefficient [START_REF] Kerstel | A water isotope ( 2 H, 17 O, and 18 O) spectrometer based on optical feedback cavity-enhanced absorption for in situ airborne applications[END_REF].

Two distinct OFCEAS spectrometers were used for the two spectral ranges covered in this work. In one setup, the probe laser was an interband cascade laser (ICL) tunable from 2850 cm -1 to 2856 cm -1 , and the baseline ring down time was 13 µs corresponding to a mirror reflectivity of 99.990 %. The other setup used a distributed feedback (DFB) laser diode emitting around 4300 cm -1 and mirrors of reflectivity 99.997 % as determined from the baseline ring down time of 45 µs.

For both setups, the cavity temperature was monitored with a thermistor of 0.3 K accuracy, and could be controlled between about 30 and 50 °C by heating bands regulated via a PID loop.

The baseline RMS noise was about 1×10 -9 cm -1 for the 4302 cm -1 setup. For the 2853 cm -1 setup, there was an additional, unexplained noise at higher temperature, so that the base line RMS noise ranged from about 5×10 -9 cm -1 at 30 °C, to 1.6×10 -8 cm -1 at 47 °C. In all cases, 100 spectra were averaged at each data point.

b. Self-continuum data acquisition

For the self-continuum measurements at 2853 cm -1 , a steel tank filled with deionised water was connected upstream of the cavity. A needle valve at the inlet of the cavity allowed adjusting the flow at a value of 3 to 4 sccm. At the outlet, an electrovalve was used to control the intra-cavity pressure, which was monitored with a Wika sensor (250 mbar full scale) calibrated against a MKS sensor (10 mbar range, 0.25 % accuracy).

A flow of water vapor through the cavity was initialized at a pressure of 20 mbar. Spectra were recorded at this pressure value, then the pressure was stepped down to approximately 5 mbar, before bringing it back up to 20 mbar. For each of those nine pressure steps, 100 spectra were averaged. This procedure was repeated for two temperature values: 30 °C and 47 °C. Figure 1 shows spectra recorded at 10, 15 and 20 mbar, for both temperature values. The rapid increase of the continuum with pressure and the significant decrease with temperature are clearly observed.

c. Foreign continuum data acquisition

A commercial humidity generator (from Omicron Technologies) was used to generate moist air for foreign continuum measurements. This generator is based on a temperature regulated membrane system to generate pure water vapor which is then mixed with the dry carrier gas (Alphagaz TM 2 synthetic air from Air Liquide) with a proportional control solenoid valve with bypass to achieve the desired humidity level, monitored via the dew point temperature measured by a chilled mirror hygrometer (Michell Instruments). A flow controller and back pressure controller (both from Bronkhorst) regulated the gas flow (300 sccm) and the pressure (1045 mbar) in the exit. A part of this flow (about 10 sccm) was derived into the OFCEAS high-finesse cavity through another flow controller, while the intra-cavity pressure was stabilized to a value of 510 Torr (680 mbar) by a Bronkhorst pressure controller at the outlet.

The recording procedure was the following. First, dry nitrogen gas was flowed through the cavity at the same pressure value of 510 Torr to record the baseline cavity mirror losses. The gas source was then switched to the moist air, and once the absorption in the cavity had reached a stable state (reflecting stability of the water mole fraction), 100 spectra were averaged before changing the water mole fraction set point to the next value. This procedure was repeated for two temperature values: 34 °C and 47 °C, and four water mole fraction values: 5000, 10000, 12500 and 15000 ppmv.

3.

Self-continuum at 2853 cm -1

In a cell filled with pure water vapor, the total absorption coefficient can be expressed as the sum of three terms:

𝛼 𝑡𝑜𝑡 (𝜈, 𝑇) = 𝛼 𝑐𝑎𝑣𝑖𝑡𝑦 + 𝛼 𝑊𝑀𝐿 + 𝛼 𝑊𝐶𝑆 (2)
where cavity, WML, WCS are the contributions due to the cavity, water vapor "monomer local lines" (WML), and water vapor self-continuum (WCS), respectively. Note that the contribution of Rayleigh scattering is negligible. The cross-section CS, expressed in cm 2 molecule -1 atm -1 , is defined by

𝛼 𝑊𝐶𝑆 = 1 𝑘𝑇 𝐶 𝑆 (𝜈, 𝑇)𝑃 𝐻 2 𝑂 2 ,
where k is the Boltzmann constant and 𝑃 𝐻 2 𝑂 is the water vapor pressure.

a. Data analysis

The absorption due to the monomer lines was subtracted using the line-by-line fitting program MATS [27]. The water vapor transitions, as well as a few formaldehyde lines which were visible in the spectrum, were modeled from HITRAN2016 [START_REF] Gordon | The HITRAN2016 Molecular Spectroscopic Database[END_REF] parameters by Voigt profiles truncated at ±25 cm -1 from the line center. The formaldehyde concentration was fitted and estimated to be on the order of 10 ppb. The HDO concentration was assumed to be 20 % lower than the natural abundance from HITRAN.

The monomer-corrected values were averaged over a 0.3 cm -1 wide part of the scan which is not much affected by the monomer lines (50 points near 2853.25 cm -1 , shown in black in Fig. 1). The obtained data points are plotted in Fig. 2 The slope of a linear regression yields the self-continuum cross-section CS. The intercept of this regression corresponds to the empty-cavity losses 𝛼 𝑐𝑎𝑣𝑖𝑡𝑦 and was subtracted in Fig. 2. The values given by the fit are reported here along with the fit uncertainty: 5.85(42)×10 -24 cm 2 molecule -1 atm -1 at 303 K, 4.28(39)×10 -24 cm 2 molecule -1 atm -1 at 320 K.

b. Comparison to literature

The different experimental determinations of the self-continuum cross-sections near room temperature in the 4 µm window are plotted in Fig. 3 together with some recent versions of the MT_CKD continuum up to the current 3.5 version. Four datasets using long-path absorption cells and covering most of the transparency window were published prior to our series of OFCEAS measurements. In 1984, Burch and Alt retrieved the continuum between 2400 and 2640 cm -1 using a grating spectrograph and a pathlength of 707 m [START_REF] Burch | Continuum absorption by H2O[END_REF][START_REF] Burch | Continuum absorption by H2O in the 700 -1200 cm -1 and[END_REF]. An optical configuration which allowed changing the number of passes through the absorption cell without perturbing the optical alignment was adopted to minimize the spectra baseline drifts. The three other studies were performed by FTS: (i) the CAVIAR consortium performed room temperature measurements at the Rutherford Appleton Laboratory with a 512.7 m pathlength [START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF], (ii) a similar FTS approach with a pathlength of 612 m at 289.5 and 287 K, was adopted at the Institute of Atmospheric Optics in Tomsk [START_REF] Ptashnik | Near-infrared water vapor self-continuum at close to room temperature[END_REF][START_REF] Ptashnik | Water vapor continuum absorption in near-IR atmospheric windows[END_REF], (iii) finally, Baranov and Lafferty, from NIST, reported FTS measurements between 311 and 363 K with a 100 m pathlength [START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF].

The OFCEAS measurements are limited by the availability of diode laser sources. Previous OFCEAS studies were performed at 2283 cm -1 [START_REF] Campargue | Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model[END_REF], 2491 cm -1 [START_REF] Richard | Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows[END_REF] and 3007 cm -1 [START_REF] Lechevallier | The water vapor self-continuum absorption in the infrared atmospheric windows: new laser measurements near 3.3 and 2.0 μm[END_REF] (see Table 1). The present measurement at 2853 cm -1 completes the sampling of the window and is found consistent with previous OFCEAS values. The comparison to the FTS values is similar to that encountered in most of the transparency windows: although reported with large error bars, the FTS values are significantly larger than the laser measurements. Strictly speaking, only CAVIAR [START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF] and NIST [START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF] measurements are available for comparison near 2850 cm -1 , Tomsk measurements [START_REF] Ptashnik | Near-infrared water vapor self-continuum at close to room temperature[END_REF][START_REF] Ptashnik | Water vapor continuum absorption in near-IR atmospheric windows[END_REF] showing a gap in the 2800-3050 cm -1 interval. Although the CAVIAR and NIST CS values of 5.0(3.2)×10 -23 and 2.6(6)×10 -23 cm 2 molecule -1 atm -1 were reported with 65% and 23% error bars, respectively, the OFCEAS value of 5.85(42)×10 -24 cm 2 molecule -1 atm -1 falls outside the (1) FTS error bars. were obtained by OFCEAS, (red circles; Campargue et al. [START_REF] Campargue | Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model[END_REF]; Richard et al. [START_REF] Richard | Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows[END_REF]; Lechevallier et al. [START_REF] Lechevallier | The water vapor self-continuum absorption in the infrared atmospheric windows: new laser measurements near 3.3 and 2.0 μm[END_REF]; this work); by FTS from Baranov and Lafferty [START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF]) (light green circles), from CAVIAR (black squares; Ptashnik et al. [START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF]), from Tomsk2013 (orange circles; Ptashnik et al. [START_REF] Ptashnik | Near-infrared water vapor self-continuum at close to room temperature[END_REF]), from Tomsk2015 (green circles; Ptashnik et al, [START_REF] Ptashnik | Water vapor continuum absorption in near-IR atmospheric windows[END_REF]) and with a grating spectrograph by Burch and Alt [START_REF] Burch | Continuum absorption by H2O[END_REF][START_REF] Burch | Continuum absorption by H2O in the 700 -1200 cm -1 and[END_REF] Over the last ten years, the different versions of the MT_CKD model in the center of the 4.0 µm window varied over one order of magnitude (Fig. 3). On the basis of the OFCEAS measurement at 2283 cm -1

(dark blue circles). Note that the plotted experimental results correspond to different temperature values (see values given in the insert

[13], the MT_CKD 3.5 version of the self-continuum has been recently decreased in the low energy edge of the window. At the 2853 cm -1 point of present interest, the MT_CKD_V3.5 CS value (8.73×10 - 24 cm 2 molecule -1 atm -1 ) is larger than the OFCEAS value by about 50 %. Similar and even more pronounced overestimation was noted at the 2490 cm -1 spectral point [START_REF] Richard | Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows[END_REF], indicating that in the very center of the window, the MT_CKD_V3.5 CS values should be significantly decreased. It is interesting to note that the pioneer results of Burch and Alt in the 2400-2640 cm -1 are the only previous measurements in reasonable agreement with OFCEAS values in this region.

c. Temperature dependence

Atmospheric modeling requires the knowledge of the temperature dependence of the water vapor selfcontinuum in particular at room temperature and below. Although the water self-continuum crosssection is decreasing rapidly with temperature (about 36% for a temperature variation of 17 K presently measured at 2853 cm -1 ), it is easier to measure the continuum at high temperature where larger saturation pressures allow for increasing considerably the water vapor pressure. For instance, the CAVIAR consortium reported measurements at temperatures from 350 to 472 K using a short-path absorption cell and vapor pressure values up to 1.6 atm [START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF]. We have collected in Fig. 4, the CS values available in the literature at different temperatures around our measurement points at 2853 cm -1 and plotted them in logarithmic scale versus 1/T. In addition to the CAVIAR room and high temperature measurements, the NIST data [START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF] cover the 311-363 K range.

The overall distribution of the experimental CS values is very similar to what was observed at several spectral points of the 4.0 and 2.1 µm windows (see Fig. 7 of Ref. [START_REF] Lechevallier | The water vapor self-continuum absorption in the infrared atmospheric windows: new laser measurements near 3.3 and 2.0 μm[END_REF], Fig. 6 of Ref. [START_REF] Richard | Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows[END_REF], Fig. 6 of Ref. The MT_CKD_V3.5 temperature dependence at 2853 cm -1 included in Fig. 4 shows a behavior close to the exp ( 𝐷 0 𝑘𝑇 ) function near room temperature while at higher temperature, the MT_CKD self-continuum is decreasing more rapidly than observed from the high temperature CAVIAR measurements.

Foreign continuum at 4302 cm -1

As mentioned above, the foreign-continuum measurements were performed at a constant total pressure of 510 Torr, for two temperature values (34°C and 47°C) and four water mole fraction values of 5000, 10000, 12500 and 15000 ppmv.

In a mixture of water vapor in air, the total absorption coefficient can be expressed as the sum of four terms:

𝛼 𝑡𝑜𝑡 (𝜈, 𝑇) = 𝛼 𝑐𝑎𝑣𝑖𝑡𝑦 + 𝛼 𝑊𝑀𝐿 + 𝛼 𝑊𝐶𝑆 + 𝛼 𝑊𝐶𝐹 = 𝛼 𝑐𝑎𝑣𝑖𝑡𝑦 + 𝛼 𝑊𝑀𝐿 + 1 𝑘𝑇 𝐶 𝑆 (𝜈, 𝑇)𝑃 𝐻 2 𝑂 2 + 1 𝑘𝑇 𝐶 𝐹 (𝜈, 𝑇)𝑃 𝐻 2 𝑂 𝑃 𝑎𝑖𝑟 (3)
where, in comparison to Eq. ( 2), the additional term 𝛼 𝑊𝐶𝐹 denotes the contribution due to the foreigncontinuum (WCF), with CF expressed in cm 2 molecule -1 atm -1 . 𝑃 𝐻 2 𝑂 and 𝑃 𝑎𝑖𝑟 are the water vapor and dry air partial pressures, respectively. Due to the negligible difference (~10 -11 cm -1 ) in Rayleigh scattering losses between the pure nitrogen baseline measurements and the moist air measurements at the same pressure, the Rayleigh contribution was omitted from Eq. (3).

a. Data analysis

In a first step, the baseline absorption 𝛼 𝑐𝑎𝑣𝑖𝑡𝑦 , measured while flowing the cavity with pure N2 at the same nominal pressure as the water mixture measurements (510 Torr), was subtracted from each spectrum. Figure 5 shows the various contributions to the remaining absorption for two values of the water vapor molar fraction. The absorption due to the water monomer lines was calculated from HITRAN2016 parameters using Voigt profiles truncated at ±25 cm -1 from the line center without including the pedestal. The isotopic abundance of HDO was reduced by 20% as compared to the HITRAN natural abundance. There were no observable lines from other species.

In this spectral region the self-continuum cross-section has been measured in a previous work [START_REF] Ventrillard | Accurate measurements and temperature dependence of the water vapor self-continuum absorption in the 2.1 μm atmospheric window[END_REF], over a temperature range comprising the temperatures studied here. We interpolated the reported CS values from Ref. [START_REF] Ventrillard | Accurate measurements and temperature dependence of the water vapor self-continuum absorption in the 2.1 μm atmospheric window[END_REF] to calculate the self-continuum absorption at our experimental conditions (CS values of 1.88×10 -23 and 1.55×10 -23 cm 2 molecule -1 atm -1 were used at 34 °C and 47 °C, respectively). Obviously, the total pressure being identical, the relative contribution of the self-continuum is larger for the higher mole fractions (see Fig. 5).

evidence a significant variation and we can merely confirm that the foreign-continuum has a small temperature dependence.

b. Comparison to literature

The comparison of the available experimental determination of the foreign-continuum cross-sections in the 2.1 µm window to the MT_CKD_V3.5 values is presented in Fig. 7. Experimental data at room temperature are limited to the present OFCEAS determination at 4310 cm -1 , the CRDS data points at 4250 cm -1 [START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF] and at 4433, 4436, 4522, 4724 and 4999 cm -1 [START_REF] Vasilchenko | The water vapor self-and foreigncontinua in the 1.6 μm and 2.3 μm windows by CRDS at room temperature[END_REF]. The CAVIAR consortium reported foreign-continuum absorption by FTS between 1.1 and 5 µm at high temperatures (350-431 K) with an absorption path length of 17.7 m [START_REF] Ptashnik | Water vapor foreign-continuum absorption in near-infrared windows from laboratory measurements[END_REF]. The chosen elevated temperatures allowed for increasing the water vapor partial pressure of the recordings between 266 and 600 mbar. Compared to our measurement conditions, these high water vapor pressure values combined with air pressure of about 4 atm led to an increase of the foreign-continuum absorption signal by two or three orders of magnitude. The FTS recordings between 350 and 431 K did not reveal temperature dependence greater than the uncertainty in those measurements. The CF values included in Fig. 7 are those reported by Ptashnik et al. at the 400 K average temperature [START_REF] Ptashnik | Water vapor foreign-continuum absorption in near-infrared windows from laboratory measurements[END_REF].

The CRDS and OFCEAS CF cross-sections values represent a consistent dataset which can be reproduced by a 4 th order polynomial fit (see Fig. 7) -the corresponding polynomial coefficients are given in the figure caption.

Overall the present OFCEAS and previous CRDS room temperature CF values are systematically below the CAVIAR values (at 400 K) by a factor between 2 and 4. In the center of the window, the FTS relative uncertainties are very large (up to 93 %) which makes the CRDS value at 4724 cm -1 fall within the 1FTS confidence interval. This is not the case on the low energy edge of the window. For instance at the 4302 cm -1 spectral point presently measured, CAVIAR CF value is 5.8(2.2)×10 -25 cm 2 molecule -1 atm - The MT_CKD_V3.5 foreign-continuum included in Fig. 7 is assumed to be temperature independent.

The MT_CKD foreign-continuum was recently increased in the 2.1 µm window, taking into account our CRDS value at 4250 cm -1 [START_REF] Vasilchenko | The water vapor self-and foreigncontinua in the 1.6 μm and 2.3 μm windows by CRDS at room temperature[END_REF] and the NIST values [START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF] in the 4.0 µm window (the MT_CKD_2.5 is included in Fig. 7, for comparison). On the low and high energy range of the window, the agreement with CRDS and OFCEAS values has become reasonable but the MT_CKD foreign-continuum should be significantly increased in the centre of the window (by a factor of about 5 for the minimum CF values near 4700 cm -1 ). [15], Ventrillard et al. [START_REF] Ventrillard | Accurate measurements and temperature dependence of the water vapor self-continuum absorption in the 2.1 μm atmospheric window[END_REF], Mondelain et al. [START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF], Vasilchenko et al. [START_REF] Vasilchenko | The water vapor self-and foreigncontinua in the 1.6 μm and 2.3 μm windows by CRDS at room temperature[END_REF] and this work); by FTS from Baranov and Lafferty [START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF]) (light green circles), from CAVIAR consortium (black squares; Ptashnik et al. [START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF]), from Tomsk2013 (orange circles; Ptashnik et al. [START_REF] Ptashnik | Near-infrared water vapor self-continuum at close to room temperature[END_REF]), from Tomsk2015 (green circles; Ptashnik et al, [START_REF] Ptashnik | Water vapor continuum absorption in near-IR atmospheric windows[END_REF]), with a grating spectrograph by Burch and Alt [START_REF] Burch | Continuum absorption by H2O[END_REF][START_REF] Burch | Continuum absorption by H2O in the 700 -1200 cm -1 and[END_REF] (dark blue circles) and by interferometric calorimetry (blue diamond;

Conclusion

Bicknell et al. [START_REF] Bicknell | Search for low-absorption regions in the 1.6-and 2.1-µm atmospheric windows[END_REF]).

The present measurements of the self-continuum cross-section of water vapor at 2853 cm -1 and of the foreign-continuum cross-sections at 4302 cm -1 complete the previous CEAS characterizations of the water vapor continuum absorption that we performed in the 4.0, 2.1, 1.6 and 1.25 µm windows. Figs. As concerns the foreign continuum, to the best of our knowledge no room temperature measurements were available prior to our OFCEAS and CRDS investigations. The overview comparison of Fig. 9 indicates that the MT_CKD_V3.5 foreign-continuum is significantly smaller than the observations near the center of the 1.6 and 2.1 µm windows. The two sets of CEAS measurements can be satisfactorily reproduced using a polynomial which is given above for the 2.1 µm window (see caption of Fig. 7) and can be found in Ref. [START_REF] Mondelaind | The water vapor foreign-continuum in the 1.6 µm window by CRDS at room temperature[END_REF] for the 1.6 µm window. The CAVIAR FTS CF values at 400 K [START_REF] Ptashnik | Water vapor foreign-continuum absorption in near-infrared windows from laboratory measurements[END_REF] are larger than the room temperature CEAS values. However, the data at disposal do not allow for a conclusive statement about the temperature dependence of the foreign continuum. In the near future, we plan to investigate this issue in more details using a newly developed CRDS cell allowing for measurements over a wider temperature range than allowed by our OFCEAS spectrometers.

Figure 1 :

 1 Figure 1: Spectra recorded with pure water vapor at three pressure values, for two temperature conditions. Black lines denote the monomer-corrected spectra used to determine the self-continuum absorption. The constant term due to the empty cavity losses, obtained from the fit (see section 3a) was subtracted.

  as a function of the squared pressure, with error bars corresponding to combined uncertainties including both statistical (type A) and type B uncertainties. Type B contributions to the uncertainty include the baseline uncertainty (2×10 -9 cm -1 ), and the uncertainty on the monomer lines, which is calculated by propagating the HITRAN error bars on the line intensities and selfbroadening coefficients. Two simulations were performed, increasing either all intensities or all self values by their HITRAN error bars, yielding deviations from the usual HITRAN simulation which were then added in quadrature.

Figure 2 :

 2 Figure 2: Self-continuum absorption 𝜶 𝑾𝑪𝑺 as a function of squared pressure, for two temperature values. The self-continuum cross-section is obtained as the slope of the linear fits. The constant term due to the cavity losses, obtained from the fit was subtracted, and shaded areas depict the fit uncertainty.

Figure 3 :

 3 Figure 3: Overview comparison of the self-continuum cross-section of water vapor near room temperature in the 4.0 µm window. Solid lines show different versions of the MT_CKD model at 296 K [2-4]. Experimental results

[ 18 ]

 18 ), our two present CS values are on line with the high temperature CAVIAR values while CAVIAR room temperature value (obtained with a different FTS cell) is strongly overestimated. As already noted for other spectral points, the OFCEAS and the CAVIAR high temperature values follow a simple exponential law in 1/T with a slope close to the dissociation energy of the water dimer, D0 ≈ 1100 cm -1[START_REF] Rocher-Casterline | Determination of the bond dissociation energy (D0) of the water dimer, (H2O)2, by velocity map imaging[END_REF].

Figure 4 :

 4 Figure 4: Temperature dependence of the water vapor self-continuum cross-sections near 2853 cm -1 obtained byOFCEAS (open red circles), by FTS (CAVIAR at high temperature[START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF] (green squares): CAVIAR at room temperature[START_REF] Ptashnik | Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements[END_REF] (full blue circle): Baranov and Lafferty[START_REF] Baranov | The water vapor self-and water-nitrogen continuum absorption in the 1000 and 2500 cm -1 atmospheric windows[END_REF] (full green circles). The MT_CKD_V3.5 values which are normalized to the number density at 1 atm and 296 K were multiplied by 296/T. The D0 slope corresponds to an exp(D0/kT) function, D0 ≈ 1100 cm -1 being the dissociation energy of the water dimer molecule.

Figure 6 :

 6 Figure 6: Foreign continuum absorption 𝜶 𝑾𝑪𝑭 as a function of the product of water vapor and air pressures, for two temperature values. The error bars shown here correspond to the combined uncertainty including both type A and type B uncertainties. The slopes of linear fits, also plotted, give the foreign continuum cross-sections CF. Shaded areas show the uncertainty on the fitted slopes.

1

  to be compared to an OFCEAS value of 2.75(6)×10 -25 cm 2 molecule -1 atm -1 at 307 K (the corresponding density normalized CF values are 7.8(3.0) and 2.85(6) cm 2 molecule -1 atm -1 ). If the CAVIAR values at 400 K are confirmed, it would indicate that the foreign-continuum exhibits significant positive temperature dependence.

Figure 7 .

 7 Figure 7. Overview of the experimental foreign-continuum cross-sections, CF, reported in the literature and retrieved in this work (red circle) for the 2.1 µm window and comparison to the MT_CKD model in its versions3.5 (red) and 2.5 (black). Previous experimental determinations are the CAVIAR FTS values at 400 K from Ref.[31] (full grey circles) and the CRDS values (light blue circles) from Vasilchenko et al.[START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF] at 4250 cm -1 ) and from Mondelain et al.[START_REF] Vasilchenko | The water vapor self-and foreigncontinua in the 1.6 μm and 2.3 μm windows by CRDS at room temperature[END_REF] at 4433, 4436, 4522, 4724, 4999 cm -1 . Note that for comparison purposes, the CF values are density normalized and are given in cm 2 molecule -1 (density normalized CF values in cm 2 molecule -1 correspond to CF values in cm 2 molecule -1 atm -1 multiplied by the factor T/296). The blue solid line corresponds to the fit of the CRDS and OFCEAS data with a 4 th order polynomial: 3.99039496×10 -21 -3.41093025×10 - 24 +1.09342553×10 -27   -1.55784737×10 -31   +8.32287078×10 -36   where is the wavenumber in cm -1 .

Figure 8 :

 8 Figure 8: Overview comparison of the self-continuum cross-section of water vapor near room temperature between 1500 and 9000 cm -1 .Solid lines show different versions of the MT_CKD V3.0 and V3.5 versions at 296 K [2-4]. Experimental resultswere obtained by OFCEAS and CRDS (red circles; Campargue et al.[START_REF] Campargue | Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model[END_REF], Richard et al.[START_REF] Richard | Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows[END_REF],Lechevallier et al.

8 and 9

 9 present an updated overview comparison of our measured CS and CF values to the MT_CKD model and to previous FTS measurements. The consistency of our measurements performed since 2013 by different experimentators, with two different CEAS techniques (CRDS and CEAS) using a large variety of spectrometers covering very different spectral regions, has to be underlined. It is now admitted that the FTS self-continuum values reported by the CAVIAR consortium at room temperature are largely overestimated in the windows because they were affected by experimental biases. The current version of the MT_CKD self-continuum has been recently constrained according to most of the CEAS crosssections in the 4.0, 2.1, 1.6 and 1.25 µm windows. The present CS measurement at 2853 cm -1 together with the previous OFCEAS measurement at the 2490 cm -1 spectral point [14], indicate the MT_CKD_V3.5 self-continuum values should be significantly decreased in the center of the 4.0 µm window.

Figure 9 .

 9 Figure 9. Overview of the experimental foreign-continuum cross-sections, CF, reported in the literature and retrieved in this work (red circle) for the 2.1 and 1.6 µm windows and comparison to the MT_CKD_V3.5 model (red solid line). Previous experimental determinations are the CAVIAR FTS values at 400 K from Ref. [31] (black circles), CRDS values (light blue circles) from Vasilchenko et al.[START_REF] Mondelain | The selfand foreignabsorption continua of water vapor by cavity ring-down spectroscopy near 2.35 µm[END_REF] at 4250 cm -1 , from Mondelain et al.[START_REF] Vasilchenko | The water vapor self-and foreigncontinua in the 1.6 μm and 2.3 μm windows by CRDS at room temperature[END_REF] at 4433, 4436, 4522, 4724, 4999 cm -1 and from Mondelain et al.[START_REF] Mondelaind | The water vapor foreign-continuum in the 1.6 µm window by CRDS at room temperature[END_REF] in the 1.6 µm window.

Table 1 .

 1 Parts 3 and 4 are devoted to the retrievals of the values of CS at 2853 cm -1 and CF at 4302 cm -1 , respectively and include a discussion of the comparison Summary of the CEAS measurements of self-continuum cross-sections, CS, in the 4.0 µm window and foreign-continuum cross-sections, CF, in the 2.1 µm window. Number in parenthesis correspond to 1 uncertainty in units of the last digit.

	Window Approx. center	Spectral point (cm -1 )	T(K)	CS (10 -23 cm 2 molecule -1 atm -1 )	Reference
		2283 (4.38 µm)	296.15 301.15	1.26(6) a 1.18(6) a	Campargue et al. 2016 [13]
			312.15	0.88(4) a
		2491 (4.014 µm)	297.3 312.3	0.41(3) 0.305(43)	Richard et al. 2017 [14]
			325.6	0.260(37)
	2700 cm -1
	(4.0 µm)

with literature data and of the temperature dependence. For the convenience of the reader, we have gathered in Table

1

, the previous and present CEAS measurements of CS in the 4.0 µm window and CF in the 2.1 µm window.

2853 (3.5 µm) 303.15 320.15 0.585(42) 0.428(39) This work

		298.15	1.96(39)
		303.15	2.17(54)
	3007 (3.3 µm)	313.15 308.15	1.43(36) 1.83(46)	Lechevallier et al. 2018 [15]
		318.15	1.82(46)
		323.15	1.40(35)
			CF
			(10 -25 cm 2 molecule -1 atm -1 )
	4248.83 4257.30	297	3.91(40) b 3.93(30) b	Mondelain et al. 2015 [16]
	4700 cm -1
	(2.1 µm)

4302 307.15 320.15 2.75(17) 2.60(18) This work

	4432.6		1.26(5)
	4436.3		1.15(5)
	4522.0	297	0.810(36)	Vasilchenko et al. 2019 [17]
	4724.1		0.444(43)
	4999.0		0.83(18)
	Notes

a Total uncertainty of 5%

Acknowledgements

This work was performed in the frame of the ANR project COMPLEAT (ANR-19-CE31-0010-01).

] 1/2 . The CS uncertainty was taken from Ref. [START_REF] Ventrillard | Accurate measurements and temperature dependence of the water vapor self-continuum absorption in the 2.1 μm atmospheric window[END_REF].

The values of 𝛼 𝑊𝐶𝐹 were averaged over the extent of the 0.6 cm -1 wavenumber range of each scan. The average values are plotted in Fig. 6 as a function of the product of the water vapor pressure 𝑃 𝐻 2 𝑂 and air pressure 𝑃 𝑎𝑖𝑟 . The error bars on this plot show the combined uncertainty including both the statistical (type A) uncertainty given by the standard deviation of the averaged spectral points, and the type B uncertainty described above.

The slope of a linear fit, weighted by the inverse of the variance of each point, gives the foreign continuum cross-section CF. The values derived from the fits are reported here along with the fit uncertainty: 2.75(17)×10 -25 cm 2 molecule -1 atm -1 at 307 K, 2.60(18)×10 -25 cm 2 molecule -1 atm -1 at 320 K.

The small temperature difference of 13 K between our two series of measurements does not allow to