text:
Isotopes of einsteinium

Einsteinium (99Es) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be discovered (in nuclear fallout from the Ivy Mike H-bomb test) was 253Es in 1952. There are 18 known radioisotopes from 240Es to 257Es, and 4 nuclear isomers. The longest-lived isotope is 252Es with a half-life of 471.7 days, or around 1.293 years.

List of isotopes

 * rowspan=3|240Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 141
 * rowspan=3|240.06895(39)#
 * rowspan=3|6.0(17) s
 * α (70%)
 * 236Bk
 * rowspan=3|4−#
 * β+ (30%)
 * 240Cf
 * β+, SF (0.16%)
 * (various)
 * rowspan=2|241Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 142
 * rowspan=2|241.06859(25)#
 * rowspan=2|$4.3 s$
 * α
 * 237Bk
 * rowspan=2|3/2−#
 * β+?
 * 241Cf
 * rowspan=3|242Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 143
 * rowspan=3|242.06957(28)#
 * rowspan=3|16.9(8) s
 * β+
 * 242Cf
 * rowspan=3|2+#
 * α (41%)
 * 238Bk
 * β+, SF (1.5%)
 * (various)
 * rowspan=2|243Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 144
 * rowspan=2|243.06951(22)#
 * rowspan=2|22.1(14) s
 * α (61%)
 * 239Bk
 * rowspan=2|(7/2+)
 * β+ (39%)
 * 243Cf
 * rowspan=3|244Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 145
 * rowspan=3|244.07088(20)#
 * rowspan=3|37(4) s
 * β+ (95%)
 * 244Cf
 * rowspan=3|6+#
 * α (5%)
 * 240Bk
 * β+, SF (0.011%)
 * (various)
 * rowspan=2|245Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 146
 * rowspan=2|245.07119(18)#
 * rowspan=2|1.11(6) min
 * β+ (51%)
 * 245Cf
 * rowspan=2|(3/2−)
 * α (49%)
 * 241Bk
 * rowspan=3 style="text-indent:1em" | 245mEs
 * rowspan=3 colspan="3" style="text-indent:2em" | 30(15)# keV
 * rowspan=3|>50# us
 * IT?
 * 245Es
 * rowspan=3|7/2+#
 * α?
 * 241Bk
 * β+?
 * 245Cf
 * rowspan=3|246Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 147
 * rowspan=3|246.072806(97)
 * rowspan=3|7.5(5) min
 * β+ (90.1%)
 * 246Cf
 * rowspan=3|4−#
 * α (9.9%)
 * 242Bk
 * β+, SF (.003%)
 * (various)
 * rowspan=3|247Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 148
 * rowspan=3|247.073622(21)
 * rowspan=3|4.55(26) min
 * β+ (93%)
 * 247Cf
 * rowspan=3|(7/2+)
 * α (7%)
 * 243Bk
 * SF?
 * (various)
 * rowspan=3|248Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 149
 * rowspan=3|248.075469(56)#
 * rowspan=3|24(3) min
 * β+ (99.75%)
 * 248Cf
 * rowspan=3|2−#
 * α (.25%)
 * 244Bk
 * β+, SF (3.5×10−4%)
 * (various)
 * rowspan=2|249Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 150
 * rowspan=2|249.076409(32)#
 * rowspan=2|102.2(6) min
 * β+ (99.43%)
 * 249Cf
 * rowspan=2|7/2+
 * α (.57%)
 * 245Bk
 * rowspan=2|250Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 151
 * rowspan=2|250.07861(11)#
 * rowspan=2|8.6(1) h
 * β+
 * 250Cf
 * rowspan=2|6(+)
 * α?
 * 246Bk
 * rowspan=2 style="text-indent:1em" | 250mEs
 * rowspan=2 colspan="3" style="text-indent:2em" | 200(150)# keV
 * rowspan=2|2.22(5) h
 * β+
 * 250Cf
 * rowspan=2|1(−)
 * α?
 * 246Bk
 * rowspan=2|251Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 152
 * rowspan=2|251.0799914(57)
 * rowspan=2|33(1) h
 * EC (99.5%)
 * 251Cf
 * rowspan=2|3/2−
 * α (.5%)
 * 247Bk
 * rowspan=2|252Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 153
 * rowspan=2|252.082979(54)
 * rowspan=2|471.7(19) d
 * α (78(2)%)
 * 248Bk
 * rowspan=2|(4+)
 * EC (22(2)%)
 * 252Cf
 * rowspan=2|253Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 154
 * rowspan=2|253.0848212(13)
 * rowspan=2|20.47(3) d
 * α
 * 249Bk
 * rowspan=2|7/2+
 * SF (8.7×10−6%)
 * (various)
 * rowspan=3|254Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 155
 * rowspan=3|254.0880243(32)
 * rowspan=3|275.7(5) d
 * α
 * 250Bk
 * rowspan=3|7+
 * β− (1.74×10−4%)
 * 254Fm
 * SF (<3×10−6%)
 * (various)
 * rowspan=5 style="text-indent:1em" | 254mEs
 * rowspan=5 colspan="3" style="text-indent:2em" | 80.4(11) keV
 * rowspan=5|39.3(2) h
 * β− (98(2)%)
 * 254Fm
 * rowspan=5|2+
 * IT (<3%)
 * 254Es
 * α (0.32(1)%)
 * 250Bk
 * EC (0.076(7)%)
 * 254Cf
 * SF (<0.045%)
 * (various)
 * rowspan=3|255Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 156
 * rowspan=3|255.090274(12)
 * rowspan=3|39.8(12) d
 * β− (92.0%)
 * 255Fm
 * rowspan=3|(7/2+)
 * α (8.0%)
 * 251Bk
 * SF (.0041%)
 * (various)
 * rowspan=2|256Es
 * rowspan=2| 99
 * rowspan=2| 157
 * rowspan=2| 256.09360(11)#
 * rowspan=2|7.6 h
 * β−
 * 256Fm
 * rowspan=2|7+#
 * β−, SF (.002%)
 * (various)
 * style="text-indent:1em" |256mEs
 * colspan="3" style="text-indent:2em" | 0(100)# keV
 * 25.4(12) min
 * β−
 * 256Fm
 * 0+#
 * rowspan=2|257Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 158
 * rowspan=2|257.09598(44)#
 * rowspan=2|7.7(2) d
 * β−
 * 257Fm
 * rowspan=2|7/2+#
 * α?
 * 253Bk
 * α (0.32(1)%)
 * 250Bk
 * EC (0.076(7)%)
 * 254Cf
 * SF (<0.045%)
 * (various)
 * rowspan=3|255Es
 * rowspan=3 style="text-align:right" | 99
 * rowspan=3 style="text-align:right" | 156
 * rowspan=3|255.090274(12)
 * rowspan=3|39.8(12) d
 * β− (92.0%)
 * 255Fm
 * rowspan=3|(7/2+)
 * α (8.0%)
 * 251Bk
 * SF (.0041%)
 * (various)
 * rowspan=2|256Es
 * rowspan=2| 99
 * rowspan=2| 157
 * rowspan=2| 256.09360(11)#
 * rowspan=2|7.6 h
 * β−
 * 256Fm
 * rowspan=2|7+#
 * β−, SF (.002%)
 * (various)
 * style="text-indent:1em" |256mEs
 * colspan="3" style="text-indent:2em" | 0(100)# keV
 * 25.4(12) min
 * β−
 * 256Fm
 * 0+#
 * rowspan=2|257Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 158
 * rowspan=2|257.09598(44)#
 * rowspan=2|7.7(2) d
 * β−
 * 257Fm
 * rowspan=2|7/2+#
 * α?
 * 253Bk
 * rowspan=2|257Es
 * rowspan=2 style="text-align:right" | 99
 * rowspan=2 style="text-align:right" | 158
 * rowspan=2|257.09598(44)#
 * rowspan=2|7.7(2) d
 * β−
 * 257Fm
 * rowspan=2|7/2+#
 * α?
 * 253Bk
 * 253Bk

title: Isotopes of einsteinium


text:
Isotopes of mendelevium

Mendelevium (101Md) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 256Md (which was also the first isotope of any element produced one atom at a time) in 1955. There are 17 known radioisotopes, ranging in atomic mass from 244Md to 260Md, and 5 isomers. The longest-lived isotope is 258Md with a half-life of 51.3 days, and the longest-lived isomer is 258mMd with a half-life of 57 minutes.

List of isotopes

 * 244Md
 * style="text-align:right" | 101
 * style="text-align:right" | 143
 * α
 * 240Es
 * α
 * 240Es
 * 240Es

 * rowspan=2|245Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 144
 * rowspan=2|245.08081(33)#
 * rowspan=2|$0.3 s$
 * α
 * 241Es
 * rowspan=2|7/2−#
 * β+ (rare)
 * 245Fm
 * style="text-indent:1em" | 245mMd
 * colspan="3" style="text-indent:2em" | 200(100)# keV
 * 0.90(25) ms
 * SF
 * (various)
 * 1/2−#
 * rowspan=2|246Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 145
 * rowspan=2|246.08171(28)#
 * rowspan=2|0.9(2) s
 * α
 * 242Es
 * rowspan=2|
 * β+?
 * 246Fm
 * rowspan=3 style="text-indent:1em" | 246mMd
 * rowspan=3 colspan="3" style="text-indent:2em" | 60(60) keV
 * rowspan=3|4.4(8) s
 * β+ (>67%)
 * 246Fm
 * rowspan=3|
 * α (<23%)
 * 242Es
 * β+, SF (>10%)
 * (various)
 * rowspan=3|247Md
 * rowspan=3 style="text-align:right" | 101
 * rowspan=3 style="text-align:right" | 146
 * rowspan=3|247.08152(22)#
 * rowspan=3|1.20(12) s
 * α (99.14%)
 * 243Es
 * rowspan=3|(7/2−)
 * SF (0.86%)
 * (various)
 * β+?
 * 247Fm
 * rowspan=2 style="text-indent:1em" | 247mMd
 * rowspan=2 colspan="3" style="text-indent:2em" | 153 keV
 * rowspan=2|0.23(3) s
 * α (80%)
 * 243Es
 * rowspan=2|(1/2−)
 * SF (20%)
 * (various)
 * rowspan=3|248Md
 * rowspan=3 style="text-align:right" | 101
 * rowspan=3 style="text-align:right" | 147
 * rowspan=3|248.08282(26)#
 * rowspan=3|7(3) s
 * β+ (80%)
 * 248Fm
 * rowspan=3|
 * α (20%)
 * 244Es
 * β+, SF (.05%)
 * (various)
 * rowspan=2|249Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 148
 * rowspan=2|249.08291(22)#
 * rowspan=2|26(1) s
 * α (75%)
 * 245Es
 * rowspan=2|(7/2−)
 * β+ (25%)
 * 249Fm
 * style="text-indent:1em" | 249mMd
 * colspan="3" style="text-indent:2em" | 100(100)# keV
 * α
 * 245Es
 * (1/2−)
 * rowspan=3|250Md
 * rowspan=3 style="text-align:right" | 101
 * rowspan=3 style="text-align:right" | 149
 * rowspan=3|250.08442(32)#
 * rowspan=3|54(4) s
 * β+ (93.0%)
 * 250Fm
 * rowspan=3|
 * α (7.0%)
 * 246Es
 * β+, SF (0.026%)
 * (various)
 * rowspan=2|251Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 150
 * rowspan=2|251.084774(20)
 * rowspan=2|4.27(26) min
 * β+ (90%)
 * 251Fm
 * rowspan=2|(7/2−)
 * α (10%)
 * 247Es
 * rowspan=2|252Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 151
 * rowspan=2|252.08643(14)#
 * rowspan=2|2.3(8) min
 * β+
 * 252Fm
 * rowspan=2|
 * α (rare)
 * 248Es
 * rowspan=2|253Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 152
 * rowspan=2|253.08714(3)#
 * rowspan=2|12(8) min [$0.33 s$]
 * β+ (~99%)
 * 253Fm
 * rowspan=2|(7/2−)
 * α (~1%)
 * 249Es
 * rowspan=2|254Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 153
 * rowspan=2|254.08959(11)#
 * rowspan=2|10(3) min
 * β+
 * 254Fm
 * rowspan=2|(0−)
 * α (rare)
 * 250Es
 * rowspan=2 style="text-indent:1em" | 254mMd
 * rowspan=2 colspan="3" style="text-indent:2em" | 50(100)# keV
 * rowspan=2|28(8) min
 * β+
 * 254Fm
 * rowspan=2|(3−)
 * α (rare)
 * 250Es
 * rowspan=3|255Md
 * rowspan=3 style="text-align:right" | 101
 * rowspan=3 style="text-align:right" | 154
 * rowspan=3|255.091084(7)
 * rowspan=3|27(2) min
 * β+ (92%)
 * 255Fm
 * rowspan=3|(7/2−)
 * α (8%)
 * 251Es
 * SF (.15%)
 * (various)
 * rowspan=2|256Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 155
 * rowspan=2|256.09389(13)#
 * rowspan=2|77(2) min
 * β+ (89%)
 * 256Fm
 * rowspan=2|(1−)
 * α (11%)
 * 252Es
 * rowspan=3|257Md
 * rowspan=3 style="text-align:right" | 101
 * rowspan=3 style="text-align:right" | 156
 * rowspan=3|257.0955424(29)
 * rowspan=3|5.52(5) h
 * EC (84.8%)
 * 257Fm
 * rowspan=3|(7/2−)
 * α (15.2%)
 * 253Es
 * SF (rare)
 * (various)
 * rowspan=3|258Md
 * rowspan=3 style="text-align:right" | 101
 * rowspan=3 style="text-align:right" | 157
 * rowspan=3|258.098431(5)
 * rowspan=3|51.59(29) d
 * α
 * 254Es
 * rowspan=3|(8−)#
 * β− (<0.0015%)
 * 258No
 * β+ (<0.0015%)
 * 258Fm
 * rowspan=4 style="text-indent:1em" | 258mMd
 * rowspan=4 colspan="3" style="text-indent:2em" | 0(200)# keV
 * rowspan=4|57.0(9) min
 * EC
 * 258Fm
 * rowspan=4|1−#
 * SF (<15%)
 * (various)
 * α (<1.2%)
 * 254Es
 * β− (rare)
 * 258No
 * rowspan=2|259Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 158
 * rowspan=2|259.10051(22)#
 * rowspan=2|1.60(6) h
 * SF
 * (various)
 * rowspan=2|7/2−#
 * α (rare)
 * 255Es
 * rowspan=4|260Md
 * rowspan=4 style="text-align:right" | 101
 * rowspan=4 style="text-align:right" | 159
 * rowspan=4|260.10365(34)#
 * rowspan=4|27.8(8) d
 * SF
 * (various)
 * rowspan=4|
 * α (<5%)
 * 256Es
 * EC (<5%)
 * 260Fm
 * β− (<3.5%)
 * 260No
 * 254Es
 * rowspan=3|(8−)#
 * β− (<0.0015%)
 * 258No
 * β+ (<0.0015%)
 * 258Fm
 * rowspan=4 style="text-indent:1em" | 258mMd
 * rowspan=4 colspan="3" style="text-indent:2em" | 0(200)# keV
 * rowspan=4|57.0(9) min
 * EC
 * 258Fm
 * rowspan=4|1−#
 * SF (<15%)
 * (various)
 * α (<1.2%)
 * 254Es
 * β− (rare)
 * 258No
 * rowspan=2|259Md
 * rowspan=2 style="text-align:right" | 101
 * rowspan=2 style="text-align:right" | 158
 * rowspan=2|259.10051(22)#
 * rowspan=2|1.60(6) h
 * SF
 * (various)
 * rowspan=2|7/2−#
 * α (rare)
 * 255Es
 * rowspan=4|260Md
 * rowspan=4 style="text-align:right" | 101
 * rowspan=4 style="text-align:right" | 159
 * rowspan=4|260.10365(34)#
 * rowspan=4|27.8(8) d
 * SF
 * (various)
 * rowspan=4|
 * α (<5%)
 * 256Es
 * EC (<5%)
 * 260Fm
 * β− (<3.5%)
 * 260No
 * SF
 * (various)
 * rowspan=4|
 * α (<5%)
 * 256Es
 * EC (<5%)
 * 260Fm
 * β− (<3.5%)
 * 260No
 * β− (<3.5%)
 * 260No
 * 260No

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Isotopes of mendelevium


text:
Mahaica-Berbice

Mahaica-Berbice (Region 5) is a region of Guyana, bordering the Atlantic Ocean to the north, the region of East Berbice-Corentyne to the east, the region of Upper Demerara-Berbice to the south and the region of Demerara-Mahaica to the west.

It contains the villages of Rosignol, Fort Wellington, and Mahaicony.

The Mahaica River runs along the region's western border. The Berbice River is the eastern border. The Mahaicony and Abary Rivers run south to north.

Population
The Government of Guyana has administered three official censuses since the 1980 administrative reforms, in 1980, 1991 and 2002. In 2012, the population of Mahaica-Berbice was recorded at 49,723 people. Official census records for the population of the Mahaica-Berbice region are as follows:

 * 2012 : 49,723
 * 2002 : 52,400
 * 1991 : 51,280
 * 1980 : 53,898

Communities
(including name variants):

 * Abary
 * Bel Air
 * Belladrum
 * Blairmont (Blairmont Place)
 * Burma
 * Bush Lot
 * Catherinas Lust
 * Cotton Tree
 * Esau and Jacob
 * Fort Wellington
 * Gordon Table
 * Governor Light
 * Hopetown
 * Ithaca
 * Jacoba
 * Lichfield (Forty-two)
 * Mahaicony (Mahaicony Village)
 * Mora Point
 * Moraikobai (Moraikobe)
 * Mortice
 * Number 4 (Edderton Village)
 * Number 7 (Blairmont)
 * Number 8 (Inverness)
 * Number 9 (Expectation)
 * Number 11 (Woodley Park)
 * Number 40 Village (Seafield, Forty)
 * Number 41 (Forty-one Village)
 * Perth (Perth Village)
 * Pine Ground
 * Rising Sun
 * Rosignol
 * Saint Francis Mission
 * Saint John
 * Tempe
 * Washington
 * Weldaad

title: Mahaica-Berbice


text:
Isotopes of nobelium

Nobelium (102No) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized (and correctly identified) was 254No in 1966. There are fourteen known radioisotopes, which are 248No to 260No and 262No, and many isomers. The longest-lived isotope is 259No with a half-life of 58 minutes. The longest-lived isomer is 251m1No with a half-life of 1.02 seconds.

List of isotopes

 * 248No
 * style="text-align:right" | 102
 * style="text-align:right" | 146
 * 248.08662(24)#
 * <2 μs
 * 0+
 * rowspan=2|249No
 * rowspan=2 style="text-align:right" | 102
 * rowspan=2 style="text-align:right" | 147
 * rowspan=2|249.0878(3)#
 * rowspan=2|38.3(28) ms
 * α
 * 245Fm
 * rowspan=2|5/2+
 * SF (<0.23%)
 * (various)
 * 245Fm
 * rowspan=2|5/2+
 * SF (<0.23%)
 * (various)
 * (various)

 * rowspan=2|250No
 * rowspan=2 style="text-align:right" | 102
 * rowspan=2 style="text-align:right" | 148
 * rowspan=2|250.08756(22)#
 * rowspan=2|4.0(4) μs
 * SF
 * (various)
 * rowspan=2|0+
 * α (rare)
 * 246Fm
 * rowspan=2 style="text-indent:1em" | 250m1No
 * rowspan=2 colspan="3" style="text-indent:2em" |~1250 keV
 * rowspan=2|23(4) μs
 * IT
 * 250No
 * rowspan=2|(6+)
 * SF (<3.5%)
 * (various)
 * style="text-indent:1em" | 250m2No
 * colspan="3" style="text-indent:2em" |
 * IT
 * 250m1No
 * rowspan=3|251No
 * rowspan=3 style="text-align:right" | 102
 * rowspan=3 style="text-align:right" | 149
 * rowspan=3|251.088945(4)
 * rowspan=3|0.80(1) s
 * α (91%)
 * 247Fm
 * rowspan=3|(7/2+)
 * β+ (9%)
 * 251Md
 * SF (0.14%)
 * (various)
 * rowspan=2 style="text-indent:1em" | 251m1No
 * rowspan=2 colspan="3" style="text-indent:2em" | 105(3) keV
 * rowspan=2|1.02(3) s
 * α
 * 247mFm
 * rowspan=2|(1/2+)
 * β+?
 * 251Md
 * style="text-indent:1em" | 251m2No
 * colspan="3" style="text-indent:2em" | >1700 keV
 * ~2 μs
 * IT
 * 251No
 * rowspan=3|252No
 * rowspan=3 style="text-align:right" | 102
 * rowspan=3 style="text-align:right" | 150
 * rowspan=3|252.088967(10)
 * rowspan=3|2.42(6) s
 * α (70.1%)
 * 248Fm
 * rowspan=3|0+
 * SF (29.1%)
 * (various)
 * β+ (0.8%)
 * 252Md
 * style="text-indent:1em" | 252m1No
 * colspan="3" style="text-indent:2em" | 1254 keV
 * 100(3) ms
 * IT
 * 252No
 * (8−)
 * style="text-indent:1em" | 252m2No
 * colspan="3" style="text-indent:2em" |
 * 921(118) μs
 * IT
 * 252No
 * rowspan=3|253No
 * rowspan=3 style="text-align:right" | 102
 * rowspan=3 style="text-align:right" | 151
 * rowspan=3|253.090564(7)
 * rowspan=3|1.57(2) min
 * α (55%)
 * 249Fm
 * rowspan=3|(9/2−)
 * β+ (45%)
 * 253Md
 * SF (rare)
 * (various)
 * style="text-indent:1em" | 253m1No
 * colspan="3" style="text-indent:2em" | 167.5(5) keV
 * 30.3(1.6) μs
 * IT
 * 253No
 * (5/2+)
 * style="text-indent:1em" | 253m2No
 * colspan="3" style="text-indent:2em" | 1196(107) keV
 * 706(24) μs
 * IT
 * 253No
 * 19/2+#
 * style="text-indent:1em" | 253m3No
 * colspan="3" style="text-indent:2em" | 1256(113) keV
 * 552(15) μs
 * IT
 * 253No
 * 25/2+#
 * rowspan=3|254No
 * rowspan=3 style="text-align:right" | 102
 * rowspan=3 style="text-align:right" | 152
 * rowspan=3|254.090956(11)
 * rowspan=3|51.2(4) s
 * α (90%)
 * 250Fm
 * rowspan=3|0+
 * β+ (10%)
 * 254Md
 * SF (0.17%)
 * (various)
 * rowspan=3 style="text-indent:1em" | 254m1No
 * rowspan=3 colspan="3" style="text-indent:2em" | 1296.4(1.1) keV
 * rowspan=3|264.9(1.4) ms
 * IT (98.0%)
 * 254No
 * rowspan=3|(8−)
 * SF (2.0%)
 * (various)
 * α (<1%)
 * 250Fm
 * rowspan=2 style="text-indent:1em" | 254m2No
 * rowspan=2 colspan="3" style="text-indent:2em" | 3217(300)# keV
 * rowspan=2|184(3) μs
 * IT
 * 254m1No
 * rowspan=2|16+#
 * SF (<1.2%)
 * (various)
 * rowspan=2|255No
 * rowspan=2 style="text-align:right" | 102
 * rowspan=2 style="text-align:right" | 153
 * rowspan=2|255.093191(16)
 * rowspan=2|3.52(18) min
 * α (61.4%)
 * 251Fm
 * rowspan=2|1/2+
 * β+ (38.6%)
 * 255Md
 * style="text-indent:1em" | 255m1No
 * colspan="3" style="text-indent:2em" | 240–300 keV
 * 109(9) μs
 * IT
 * 255No
 * (11/2−)
 * style="text-indent:1em" | 255m2No
 * colspan="3" style="text-indent:2em" | 1400–1600 keV
 * 77(6) μs
 * IT
 * 255m1No
 * (19/2,21/2,23/2)
 * style="text-indent:1em" | 255m3No
 * colspan="3" style="text-indent:2em" | ≥1500 keV
 * IT
 * 255m1No
 * (≥19/2)
 * rowspan=3|256No
 * rowspan=3 style="text-align:right" | 102
 * rowspan=3 style="text-align:right" | 154
 * rowspan=3|256.094283(8)
 * rowspan=3|2.91(5) s
 * α (99.47%)
 * 252Fm
 * rowspan=3|0+
 * SF (0.53%)
 * (various)
 * EC (rare)
 * 256Md
 * style="text-indent:1em" | 256mNo
 * colspan="3" style="text-indent:2em" |
 * IT
 * 256No
 * (5−,7−)
 * rowspan=2|257No
 * rowspan=2 style="text-align:right" | 102
 * rowspan=2 style="text-align:right" | 155
 * rowspan=2|257.096888(7)
 * rowspan=2|24.5(5) s
 * α
 * 253Fm
 * rowspan=2|(3/2+)
 * β+ (rare)
 * 257Md
 * rowspan=2|258No
 * rowspan=2 style="text-align:right" | 102
 * rowspan=2 style="text-align:right" | 156
 * rowspan=2|258.09821(11)#
 * rowspan=2|1.23(12) ms
 * SF
 * (various)
 * rowspan=2|0+
 * α (rare)
 * 254Fm
 * rowspan=3|259No
 * rowspan=3 style="text-align:right" | 102
 * rowspan=3 style="text-align:right" | 157
 * rowspan=3|259.10103(11)#
 * rowspan=3|58(5) min
 * α (75%)
 * 255Fm
 * rowspan=3|9/2+
 * EC (25%)
 * 259Md
 * SF (<10%) )
 * (various)
 * 260No
 * style="text-align:right" | 102
 * style="text-align:right" | 158
 * 260.10264(22)#
 * 106(8) ms
 * SF
 * (various)
 * 0+
 * colspan="3" style="text-indent:2em" |
 * IT
 * 256No
 * (5−,7−)
 * rowspan=2|257No
 * rowspan=2 style="text-align:right" | 102
 * rowspan=2 style="text-align:right" | 155
 * rowspan=2|257.096888(7)
 * rowspan=2|24.5(5) s
 * α
 * 253Fm
 * rowspan=2|(3/2+)
 * β+ (rare)
 * 257Md
 * rowspan=2|258No
 * rowspan=2 style="text-align:right" | 102
 * rowspan=2 style="text-align:right" | 156
 * rowspan=2|258.09821(11)#
 * rowspan=2|1.23(12) ms
 * SF
 * (various)
 * rowspan=2|0+
 * α (rare)
 * 254Fm
 * rowspan=3|259No
 * rowspan=3 style="text-align:right" | 102
 * rowspan=3 style="text-align:right" | 157
 * rowspan=3|259.10103(11)#
 * rowspan=3|58(5) min
 * α (75%)
 * 255Fm
 * rowspan=3|9/2+
 * EC (25%)
 * 259Md
 * SF (<10%) )
 * (various)
 * 260No
 * style="text-align:right" | 102
 * style="text-align:right" | 158
 * 260.10264(22)#
 * 106(8) ms
 * SF
 * (various)
 * 0+
 * 260No
 * style="text-align:right" | 102
 * style="text-align:right" | 158
 * 260.10264(22)#
 * 106(8) ms
 * SF
 * (various)
 * 0+
 * 0+

 * 262No
 * style="text-align:right" | 102
 * style="text-align:right" | 160
 * 262.10746(39)#
 * ~5 ms
 * SF
 * (various)
 * 0+
 * 0+

Cold fusion
This cold fusion reaction was first studied in 1979 at Flerov Laboratory of Nuclear Reactions (FLNR). Further work in 1988 at GSI measured EC and SF branchings in 254No. In 1989, the FLNR used the reaction to measure SF decay characteristics for the two isomers of 254No. The measurement of the 2n excitation function was reported in 2001 by Yuri Oganessian at the FLNR.
 * 208Pb(48Ca,xn)256−xNo (x=1,2,3,4)

Patin et al. at the LBNL reported in 2002 the synthesis of 255–251No in the 1-4n exit channels and measured further decay data for these isotopes.

The reaction has recently been used at Jyväskylän Yliopisto Fysiikan Laitos (JYFL) using the RITU set-up to study K-isomerism in 254No. The scientists were able to measure two K-isomers with half-lives of 275 ms and 198 s, respectively. They were assigned to 8− and 16+ K-isomeric levels.

The reaction was used in 2004–5 at the FLNR to study the spectroscopy of 255–253No. The team were able to confirm an isomeric level in 253No with a half-life of 43.5 s.

This reaction was studied in 2003 at the FLNR in a study of the spectroscopy of 250No.
 * 208Pb(44Ca,xn)252−xNo (x=2)

The measurement of the 2n excitation function for this reaction was reported in 2001 by Yuri Oganessian and co-workers at the FLNR. The reaction was used in 2004–5 to study the spectroscopy of 253No.
 * 207Pb(48Ca,xn)255−xNo (x=2)

The measurement of the 1-4n excitation functions for this reaction were reported in 2001 by Yuri Oganessian and co-workers at the FLNR. The 2n channel was further studied by the GSI to provide a spectroscopic determination of K-isomerism in 252No. A K-isomer with spin and parity 8− was detected with a half-life of 110 ms.
 * 206Pb(48Ca,xn)254−xNo (x=1,2,3,4)

The measurement of the 2n excitation function for this reaction was reported in 2001 by Yuri Oganessian at the FLNR. They reported a new isotope 250No with a half-life of 36 μs. The reaction was used in 2003 to study the spectroscopy of 250No.They were able to observe two spontaneous fission activities with half-lives of 5.6 μs and 54 μs and assigned to 250No and 249No, respectively. The latter activity was later assigned to a K-isomer in 250No. The reaction was reported in 2006 by Peterson et al. at the Argonne National Laboratory (ANL) in a study of SF in 250No. They detected two activities with half-lives of 3.7 μs and 43  μs and both assigned to 250No, the latter associated with a K-isomer. In 2020, a team at FLNR repeated this reaction and found a new 9.1-MeV alpha particle activity correlated to 245Fm and 241Cf, which they assigned to the new isotope 249No.
 * 204Pb(48Ca,xn)252−xNo (x=2,3)

Hot fusion
The cross sections for the 4-6n exit channels have been measured for this reaction at the FLNR.
 * 232Th(26Mg,xn)258−xNo (x=4,5,6)

This reaction was first studied in 1964 at FLNR. The team were able to detect decays from 252Fm and 250Fm. The 252Fm activity was associated with an ~8 s half-life and assigned to 256102 from the 4n channel, with a yield of 45 nb. They were also able to detect a 10 s spontaneous fission activity also tentatively assigned to 256102. Further work in 1966 on the reaction examined the detection of 250Fm decay using chemical separation and a parent activity with a half-life of ~50 s was reported and correctly assigned to 254102. They also detected a 10 s spontaneous fission activity tentatively assigned to 256102. The reaction was used in 1969 to study some initial chemistry of nobelium at the FLNR. They determined eka-ytterbium properties, consistent with nobelium as the heavier homologue. In 1970, they were able to study the SF properties of 256No. In 2002, Patin et al. reported the synthesis of 256No from the 4n channel but were unable to detect 257No.
 * 238U(22Ne,xn)260−xNo (x=4,5,6)

The cross section values for the 4-6n channels have also been studied at the FLNR.

This reaction was studied in 1964 at FLNR. No spontaneous fission activities were observed.
 * 238U(20Ne,xn)258−xNo

The cross sections for the 4-6n exit channels have been measured for this reaction at the FLNR.
 * 236U(22Ne,xn)258−xNo (x=4,5,6)

This reaction was studied in 1970 at the FLNR. It was used to study the SF decay properties of 252No.
 * 235U(22Ne,xn)257−xNo (x=5)

The synthesis of neutron deficient nobelium isotopes was studied in 1975 at the FLNR. In their experiments they observed a 250 s SF activity, which they tentatively assigned to 250No in the 5n exit channel. Later results have not been able to confirm this activity and it is currently unidentified.
 * 233U(22Ne,xn)255−xNo

This reaction was studied in 1966 at the FLNR. The team identified an 8.2 s SF activity tentatively assigned to 256102.
 * 242Pu(18O,xn)260−xNo (x=4?)

This reaction was first studied in 1958 at the FLNR. The team measured ~8.8 MeV alpha particles with a half-life of 30 s and assigned to 253,252,251102. A repeat in 1960 produced 8.9 MeV alpha particles with a half-life of 2–40 s and assigned to 253102 from the 4n channel. Confidence in these results was later diminished.
 * 241Pu(16O,xn)257−xNo

This reaction was studied in 1970 at the FLNR in an effort to study the SF decay properties of 252No.
 * 239Pu(18O,xn)257−xNo (x=5)

This reaction was first studied in 1958 at the FLNR. The team were able to measure ~8.8 MeV alpha particles with a half-life of 30 s and assigned to253,252,251102. A repeat in 1960 was unsuccessful and it was concluded the first results were probably associated with background effects.
 * 239Pu(16O,xn)255−xNo

This reaction was studied in 1966 at the FLNR. The team were able to detect 250Fm using chemical techniques and determined an associated half-life significantly higher than the reported 3 s by Berkeley for the supposed parent 254No. Further work later the same year measured 8.1 MeV alpha particles with a half-life of 30–40 s.
 * 243Am(15N,xn)258−xNo (x=4)

This reaction was studied in 1966 at the FLNR. They were unable to detect the 8.1 MeV alpha particles detected when using a N-15 beam.
 * 243Am(14N,xn)257−xNo

The decay properties of 252No were examined in 1977 at Oak Ridge. The team calculated a half-life of 2.3 s and measured a 27% SF branching.
 * 241Am(15N,xn)256−xNo (x=4)

The synthesis of the new isotope 259No was reported in 1973 from the LBNL using this reaction.
 * 248Cm(18O,αxn)262−xNo (x=3)

This reaction was first studied in 1967 at the LBNL. The new isotopes 258No,257No and 256No were detected in the 3-5n channels. The reaction was repeated in 1970 to provide further decay data for 257No.
 * 248Cm(13C,xn)261−xNo (x=3?,4,5)

This reaction was studied in 1967 at the LBNL in their seminal study of nobelium isotopes. The reaction was used in 1990 at the LBNL to study the SF of256No.
 * 248Cm(12C,xn)260−xNo (4,5?)

This reaction was studied in 1967 at the LBNL in their seminal study of nobelium isotopes.
 * 246Cm(13C,xn)259−xNo (4?,5?)

This reaction was studied in 1958 by scientists at the LBNL using a 5% 246Cm curium target. They were able to measure 7.43 MeV decays from250Fm, associated with a 3 s 254No parent activity, resulting from the 4n channel. The 3 s activity was later reassigned to 252No, resulting from reaction with the predominant 244Cm component in the target. It could however not be proved that it was not due to the contaminant250mFm, unknown at the time. Later work in 1959 produced 8.3 MeV alpha particles with a half-life of 3 s and a 30% SF branch. This was initially assigned to 254No and later reassigned to 252No, resulting from reaction with the 244Cm component in the target. The reaction was restudied in 1967 and activities assigned to 254No and 253No were detected.
 * 246Cm(12C,xn)258−xNo (4,5)

This reaction was first studied in 1957 at the Nobel Institute in Stockholm. The scientists detected 8.5 MeV alpha particles with a half-life of 10 minutes. The activity was assigned to 251No or 253No. The results were later dismissed as background. The reaction was repeated by scientists at the LBNL in 1958 but they were unable to confirm the 8.5 MeV alpha particles. The reaction was further studied in 1967 at the LBNL and an activity assigned to 253No was measured.
 * 244Cm(13C,xn)257−xNo (x=4)

This reaction was studied in 1958 by scientists at the LBNL using a 95% 244Cm curium target. They were able to measure 7.43 MeV decays from250Fm, associated with a 3 s 254No parent activity, resulting from the reaction (246Cm,4n). The 3 s activity was later reassigned to252No, resulting from reaction (244Cm,4n). It could however not be proved that it was not due to the contaminant 250mFm, unknown at the time. Later work in 1959 produced 8.3 MeV alpha particles with a half-life of 3 s and a 30% SF branch. This was initially assigned to 254No and later reassigned to 252No, resulting from reaction with the 244Cm component in the target. The reaction was restudied in 1967 at the LBNL and a new activity assigned to 251No was measured.
 * 244Cm(12C,xn)256−xNo (x=4,5)

This reaction was studied at the LBNL in 1961 as part of their search for element 104. They detected 8.2 MeV alpha particles with a half-life of 15 s. This activity was assigned to a Z=102 isotope. Later work suggests an assignment to 257No, resulting most likely from the α3n channel with the 252Cf component of the californium target.
 * 252Cf(12C,αxn)260−xNo (x=3?)

This reaction was studied at the LBNL in 1961 as part of their search for element 103. They detected 8.2 MeV alpha particles with a half-life of 15 s. This activity was assigned to a Z=102 isotope. Later work suggests an assignment to 257No, resulting most likely from the p5n channel with the 252Cf component of the californium target.
 * 252Cf(11B,pxn)262−xNo (x=5?)

This reaction was first studied in 1970 at the LBNL in a study of 255No. It was studied in 1971 at the Oak Ridge Laboratory. They were able to measure coincident Z=100 K X-rays from 255No, confirming the discovery of the element.
 * 249Cf(12C,αxn)257−xNo (x=2)

As decay products
Isotopes of nobelium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:

Isotopes
Twelve radioisotopes of nobelium have been characterized, with the most stable being 259No with a half-life of 58 minutes. Longer half-lives are expected for the as-yet-unknown 261No and 263No. An isomeric level has been found in 253No and K-isomers have been found in 250No, 252No and 254No to date.

 * Chronology of isotope discovery

Nuclear isomerism
The study of K-isomerism was recently studied by physicists at the University of Jyväskylä physics laboratory (JYFL). They were able to confirm a previously reported K-isomer and detected a second K-isomer. They assigned spins and parities of 8− and 16+ to the two K-isomers.
 * 254No

In 1971, Bemis et al. was able to determine an isomeric level decaying with a half-life of 31 s from the decay of 257Rf. This was confirmed in 2003 at the GSI by also studying the decay of 257Rf. Further support in the same year from the FLNR appeared with a slightly higher half-life of 43.5 s, decaying by M2 gamma emission to the ground state.
 * 253No

In a recent study by the GSI into K-isomerism in even-even isotopes, a K-isomer with a half-life of 110 ms was detected for 252No. A spin and parity of 8− was assigned to the isomer.
 * 252No

In 2003, scientists at the FLNR reported that they had been able to synthesise 249No, which decayed by SF with a half-life of 54 μs. Further work in 2006 by scientists at the ANL showed that the activity was actually due to a K-isomer in 250No. The ground state isomer was also detected with a very short half-life of 3.7 μs.
 * 250No

Cold fusion
The table below provides cross-sections and excitation energies for cold fusion reactions producing nobelium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Hot fusion
The table below provides cross-sections and excitation energies for hot fusion reactions producing nobelium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Retracted isotopes
In 2003, scientists at the FLNR claimed to have discovered 249No, which would have been the lightest known isotope of nobelium. However, subsequent work showed that the 54 μs fission activity instead originated from an excited state of 250No. The discovery of this isotope was later reported in 2020; its decay properties differed from the 2003 claims.

title: Isotopes of nobelium


text:
Isotopes of lawrencium

Lawrencium (103Lr) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 258Lr in 1961. There are fourteen known isotopes from 251Lr to 266Lr, and seven isomers. The longest-lived known isotope is 266Lr with a half-life of 11 hours.

List of isotopes

 * rowspan=2|251Lr
 * rowspan=2 style="text-align:right" | 103
 * rowspan=2 style="text-align:right" | 148
 * rowspan=2|251.09418(32)#
 * rowspan=2|$24.4 ms$
 * α
 * 247Md
 * rowspan=2|7/2−
 * SF
 * (various)
 * style="text-indent:1em" | 251mLr
 * colspan="3" style="text-indent:2em" | 117(27) keV
 * α
 * 247Md
 * 1/2−
 * rowspan=3|252Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 149
 * rowspan=3|252.09526(26)#
 * rowspan=3|369(75) ms [$42 ms$]
 * α (~98%)
 * 248Md
 * rowspan=3|
 * SF (~2%)
 * (various)
 * β+?
 * 252No
 * rowspan=3|253Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 150
 * rowspan=3|253.09509(22)#
 * rowspan=3|632(46) ms
 * α (>97%)
 * 249Md
 * rowspan=3|(7/2−)
 * SF (1.0%)
 * (various)
 * β+ (<2%)
 * 253No
 * rowspan=3 style="text-indent:1em" | 253mLr
 * rowspan=3 colspan="3" style="text-indent:2em" | 30(100)# keV
 * rowspan=3|1.32(14) s
 * α (>86%)
 * 249Md
 * rowspan=3|(1/2−)
 * SF (12%)
 * (various)
 * β+ (<2%)
 * 253No
 * rowspan=3|254Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 151
 * rowspan=3|254.096240(100)
 * rowspan=3|11.9(9) s
 * α (71.7%)
 * 250Md
 * rowspan=3|(4+)
 * β+ (28.3%)
 * 254No
 * SF (<0.1%)
 * (various)
 * rowspan=3 style="text-indent:1em" | 254mLr
 * rowspan=3 colspan="3" style="text-indent:2em" | 110(6) keV
 * rowspan=3|20.3(4.2) s
 * α
 * 250Md
 * rowspan=3|(1-)
 * β+
 * 254No
 * IT?
 * 254Lr
 * rowspan=3|255Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 152
 * rowspan=3|255.096562(19)
 * rowspan=3|31.1(1.1) s
 * α (85%)
 * 251Md
 * rowspan=3|1/2−
 * β+ (15%)
 * 255No
 * SF (rare)
 * (various)
 * rowspan=2 style="text-indent:1em" | 255m1Lr
 * rowspan=2 colspan="3" style="text-indent:2em" | 32(2) keV
 * rowspan=2|2.54(5) s
 * IT (~60%)
 * 255Lr
 * rowspan=2|(7/2−)
 * α (~40%)
 * 251Md
 * style="text-indent:1em" | 255m2Lr
 * colspan="3" style="text-indent:2em" | 796(12) keV
 * <1 μs
 * IT
 * 255m1Lr
 * (15/2+)
 * style="text-indent:1em" | 255m3Lr
 * colspan="3" style="text-indent:2em" | 1465(12) keV
 * 1.78(0.05) ms
 * IT
 * 255m2Lr
 * (25/2+)
 * rowspan=3|256Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 153
 * rowspan=3|256.09849(9)
 * rowspan=3|27.9(1.0) s
 * α (85%)
 * 252Md
 * rowspan=3|(0-,3-)#
 * β+ (15%)
 * 256No
 * SF (<0.03%)
 * (various)
 * rowspan=3|257Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 154
 * rowspan=3|257.09942(5)#
 * rowspan=3|$0.36 s$
 * α
 * 253Md
 * rowspan=3|(9/2+,7/2-)
 * β+ (rare)
 * 257No
 * SF (rare)
 * (various)
 * rowspan=2 style="text-indent:1em" | 257mLr
 * rowspan=2 colspan="3" style="text-indent:2em" | 100(50)# keV
 * rowspan=2|$1.24 s$
 * α
 * 253Md
 * rowspan=2|(1/2−)
 * IT
 * 257Lr
 * rowspan=2|258Lr
 * rowspan=2 style="text-align:right" | 103
 * rowspan=2 style="text-align:right" | 155
 * rowspan=2|258.10176(11)#
 * rowspan=2|$200 ms$
 * α (97.4%)
 * 254Md
 * rowspan=2|
 * β+ (2.6%)
 * 258No
 * rowspan=3|259Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 156
 * rowspan=3|259.10290(8)#
 * rowspan=3|6.2(3) s
 * α (78%)
 * 255Md
 * rowspan=3|1/2-#
 * SF (22%)
 * (various)
 * β+ (rare)
 * 259No
 * rowspan=3|260Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 157
 * rowspan=3|260.10551(13)#
 * rowspan=3|3.0(5) min
 * α (80%)
 * 256Md
 * rowspan=3|
 * β+ (20%)
 * 260No
 * SF (rare)
 * (various)
 * rowspan=2|261Lr
 * rowspan=2 style="text-align:right" | 103
 * rowspan=2 style="text-align:right" | 158
 * rowspan=2|261.10688(22)#
 * rowspan=2|39(12) min
 * SF
 * (various)
 * rowspan=2|1/2-#
 * α (<10%)
 * 257Md
 * rowspan=3|262Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 159
 * rowspan=3|262.10961(22)#
 * rowspan=3|~4 h
 * β+
 * 262No
 * rowspan=3|
 * SF (<10%)
 * (various)
 * α (<7.5%)
 * 258Md
 * 264Lr
 * style="text-align:right" | 103
 * style="text-align:right" | 161
 * 264.11420(47)#
 * $3.54 s$ h
 * SF
 * (various)
 * 266Lr
 * style="text-align:right" | 103
 * style="text-align:right" | 163
 * 266.11983(56)#
 * 22(14) h [$4.8$]
 * SF
 * (various)
 * β+ (20%)
 * 260No
 * SF (rare)
 * (various)
 * rowspan=2|261Lr
 * rowspan=2 style="text-align:right" | 103
 * rowspan=2 style="text-align:right" | 158
 * rowspan=2|261.10688(22)#
 * rowspan=2|39(12) min
 * SF
 * (various)
 * rowspan=2|1/2-#
 * α (<10%)
 * 257Md
 * rowspan=3|262Lr
 * rowspan=3 style="text-align:right" | 103
 * rowspan=3 style="text-align:right" | 159
 * rowspan=3|262.10961(22)#
 * rowspan=3|~4 h
 * β+
 * 262No
 * rowspan=3|
 * SF (<10%)
 * (various)
 * α (<7.5%)
 * 258Md
 * 264Lr
 * style="text-align:right" | 103
 * style="text-align:right" | 161
 * 264.11420(47)#
 * $11 h$ h
 * SF
 * (various)
 * 266Lr
 * style="text-align:right" | 103
 * style="text-align:right" | 163
 * 266.11983(56)#
 * 22(14) h [⇭⇭⇭]
 * SF
 * (various)
 * (various)
 * 266Lr
 * style="text-align:right" | 103
 * style="text-align:right" | 163
 * 266.11983(56)#
 * 22(14) h [⇭⇭⇭]
 * SF
 * (various)
 * SF
 * (various)

Cold fusion
This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Evidence was provided for the formation of 253Lr in the 2n exit channel. In 2022, two states (253Lr and 253mLr) were found.
 * 205Tl(50Ti,xn)255−xLr (x=2)

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. In 2022, two states (251Lr and 251mLr) were found.
 * 203Tl(50Ti,xn)253−xLr (x=2)

This reaction was reported in 1984 by Yuri Oganessian at the FLNR. The team was able to detect decays of 246Cf, a descendant of 254Lr.
 * 208Pb(48Ti,pxn)255−xLr (x=1?)

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Results are not readily available.
 * 208Pb(45Sc,xn)253−xLr

This reaction has been used to study the spectroscopic properties of 255Lr. The team at GANIL used the reaction in 2003 and the team at the FLNR used it between 2004–2006 to provide further information for the decay scheme of 255Lr. The work provided evidence for an isomeric level in 255Lr.
 * 209Bi(48Ca,xn)257−xLr (x=2)

Hot fusion
This reaction was first studied in 1965 by the team at the FLNR. They were able to detect activity with a characteristic decay of 45 seconds, which was assigned to256Lr or 257Lr. Later work suggests an assignment to 256Lr. Further studies in 1968 produced an 8.35–8.60 MeV alpha activity with a half-life of 35 seconds. This activity was also initially assigned to 256Lr or 257Lr and later to solely 256Lr.
 * 243Am(18O,xn)261−xLr (x=5)

This reaction was studied in 1970 by the team at the FLNR. They were able to detect an 8.38 MeV alpha activity with a half-life of 20s. This was assigned to255Lr.
 * 243Am(16O,xn)259−xLr (x=4)

This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to assign alpha activities to260Lr,259Lr and 258Lr from the 3-5n exit channels.
 * 248Cm(15N,xn)263−xLr (x=3,4,5)

This reaction was studied in 1988 at the LBNL in order to assess the possibility of producing 262Lr and 261Lr without using the exotic 254Es target. It was also used to attempt to measure an electron capture (EC) branch in 261mRf from the 5n exit channel. After extraction of the Lr(III) component, they were able to measure the spontaneous fission of 261Lr with an improved half-life of 44 minutes. The production cross-section was 700 pb. On this basis, a 14% electron capture branch was calculated if this isotope was produced via the 5n channel rather than the p4n channel. A lower bombarding energy (93 MeV c.f. 97 MeV) was then used to measure the production of 262Lr in the p3n channel. The isotope was successfully detected and a yield of 240 pb was measured. The yield was lower than expected compared to the p4n channel. However, the results were judged to indicate that the 261Lr was most likely produced by a p3n channel and an upper limit of 14% for the electron capture branch of 261mRf was therefore suggested.
 * 248Cm(18O,pxn)265−xLr (x=3,4)

This reaction was studied briefly in 1958 at the LBNL using an enriched 244Cm target (5% 246Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25 seconds. Later results suggest a tentative assignment to 257Lr from the 3n channel
 * 246Cm(14N,xn)260−xLr (x=3?)

This reaction was studied briefly in 1958 at the LBNL using an enriched 244Cm target (5% 246Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25s. Later results suggest a tentative assignment to 257Lr from the 3n channel with the 246Cm component. No activities assigned to reaction with the 244Cm component have been reported.
 * 244Cm(14N,xn)258−xLr

This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to detect an activity assigned to 260Lr. The reaction was further studied in 1988 to study the aqueous chemistry of lawrencium. A total of 23 alpha decays were measured for 260Lr, with a mean energy of 8.03 MeV and an improved half-life of 2.7 minutes. The calculated cross-section was 8.7 nb.
 * 249Bk(18O,αxn)263−xLr (x=3)

This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% 252Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to 257Lr. Later results suggest a reassignment to 258Lr, resulting from the 5n exit channel. The 8.4 MeV activity was also assigned to 257Lr. Later results suggest a reassignment to 256Lr. This is most likely from the 33% 250Cf component in the target rather than from the 7n channel. The 8.2 MeV was subsequently associated with nobelium.
 * 252Cf(11B,xn)263−xLr (x=5,7??)

This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% 252Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to 257Lr. Later results suggest a reassignment to 258Lr. The 8.4 MeV activity was also assigned to 257Lr. Later results suggest a reassignment to 256Lr. The 8.2 MeV was subsequently associated with nobelium.
 * 252Cf(10B,xn)262−xLr (x=4,6)

This reaction was studied in 1971 at the LBNL. They were able to identify a 0.7s alpha activity with two alpha lines at 8.87 and 8.82 MeV. This was assigned to257Lr.
 * 250Cf(14N,αxn)260−xLr (x=3)

This reaction was first studied in 1970 at the LBNL in an attempt to study the aqueous chemistry of lawrencium. They were able to measure a Lr3+ activity. The reaction was repeated in 1976 at Oak Ridge and 26s 256Lr was confirmed by measurement of coincident X-rays.
 * 249Cf(11B,xn)260−xLr (x=4)

This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activity assigned to 258Lr from the p2n channel.
 * 249Cf(12C,pxn)260−xLr (x=2)

This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activities assigned to 258Lr and 257Lr from the α2n and α3n and channels. The reaction was repeated in 1976 at Oak Ridge and the synthesis of 258Lr was confirmed.
 * 249Cf(15N,αxn)260−xLr (x=2,3)

This reaction was studied in 1987 at the LLNL. They were able to detect new spontaneous fission (SF) activities assigned to 261Lr and 262Lr, resulting from transfer from the 22Ne nuclei to the 254Es target. In addition, a 5 ms SF activity was detected in delayed coincidence with nobelium K-shell X-rays and was assigned to 262No, resulting from the electron capture of 262Lr.
 * 254Es + 22Ne – transfer

Decay products
Isotopes of lawrencium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:

Isotopes
Fourteen isotopes of lawrencium plus seven isomers have been synthesized with 266Lr being the longest-lived and the heaviest, with a half-life of 11 hours. 251Lr is the lightest isotope of lawrencium to be produced to date.

Lawrencium-253 isomers
A study of the decay properties of 257Db (see dubnium) in 2001 by Hessberger et al. at the GSI provided some data for the decay of 253Lr. Analysis of the data indicated the population of an isomeric level in 253Lr from the decay of the corresponding isomer in 257Db. The ground state was assigned spin and parity of 7/2−, decaying by emission of an 8794 keV alpha particle with a half-life of 0.57 s. The isomeric level was assigned spin and parity of 1/2−, decaying by emission of an 8722 keV alpha particle with a half-life of 1.49 s.

Lawrencium-255 isomers
Recent work on the spectroscopy of 255Lr formed in the reaction 209Bi(48Ca,2n)255Lr has provided evidence for an isomeric level.

title: Isotopes of lawrencium


text:
Isotopes of rutherfordium

Rutherfordium (104Rf) is a synthetic element and thus has no stable isotopes. A standard atomic weight cannot be given. The first isotope to be synthesized was either 259Rf in 1966 or 257Rf in 1969. There are 16 known radioisotopes from 253Rf to 270Rf (3 of which, 266Rf, 268Rf, and 270Rf, are unconfirmed) and several isomers. The longest-lived isotope is 267Rf with a half-life of 48 minutes, and the longest-lived isomer is 263mRf with a half-life of 8 seconds.

List of isotopes

 * rowspan=2|253Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 149
 * rowspan=2|253.10044(44)#
 * rowspan=2|9.9(1.2) ms
 * SF (83%)
 * (various)
 * rowspan=2|(1/2+)
 * α (17%)
 * 249No
 * style="text-indent:1em" | 253m1Rf
 * colspan="3" style="text-indent:2em" | 200(150)# keV
 * 52.8(4.4) μs
 * SF
 * (various)
 * (7/2+)
 * style="text-indent:1em" | 253m2Rf
 * colspan="3" style="text-indent:2em" | >1020 keV
 * IT
 * 253m1Rf
 * rowspan=2|254Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 150
 * rowspan=2|254.10005(30)#
 * rowspan=2|23.2(1.1) μs
 * SF (100%)
 * (various)
 * rowspan=2|0+
 * α (<1.5%)
 * 250No
 * style="text-indent:1em" | 254m1Rf
 * colspan="3" style="text-indent:2em" | >1350 keV
 * 4.7(1.1) μs
 * IT
 * 254Rf
 * (8-)
 * style="text-indent:1em" | 254m2Rf
 * colspan="3" style="text-indent:2em" |
 * 247(73) μs
 * IT
 * 254m1Rf
 * (16+)
 * rowspan=3|255Rf
 * rowspan=3 style="text-align:right" | 104
 * rowspan=3 style="text-align:right" | 151
 * rowspan=3|255.10127(12)#
 * rowspan=3|1.69(3) s
 * SF (50.9%)
 * (various)
 * rowspan=3|(9/2−)
 * α (49.1%)
 * 251No
 * β+ (<6%)
 * 255Lr
 * style="text-indent:1em" | 255m1Rf
 * colspan="3" style="text-indent:2em" | 150 keV
 * 50(17) μs
 * IT
 * 255Rf
 * (5/2+)
 * style="text-indent:1em" | 255m2Rf
 * colspan="3" style="text-indent:2em" | 1103 keV
 * IT
 * 255Rf
 * (19/2+)
 * style="text-indent:1em" | 255m3Rf
 * colspan="3" style="text-indent:2em" | 1303 keV
 * IT
 * 255Rf
 * (25/2+)
 * rowspan=2|256Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 152
 * rowspan=2|256.101152(19)
 * rowspan=2|6.67(9) ms
 * SF (99.68%)
 * (various)
 * rowspan=2|0+
 * α (0.32%)
 * 252No
 * style="text-indent:1em" | 256m1Rf
 * colspan="3" style="text-indent:2em" | ~1120 keV
 * 25(2) μs
 * IT
 * 256Rf
 * style="text-indent:1em" | 256m2Rf
 * colspan="3" style="text-indent:2em" | ~1400 keV
 * 17(2) μs
 * IT
 * 256m1Rf
 * style="text-indent:1em" | 256m3Rf
 * colspan="3" style="text-indent:2em" | >2200 keV
 * 27(5) μs
 * IT
 * 256m2Rf
 * rowspan=3|257Rf
 * rowspan=3 style="text-align:right" | 104
 * rowspan=3 style="text-align:right" | 153
 * rowspan=3|257.102917(12)
 * rowspan=3|$0.66 ms$
 * α (89.3%)
 * 253No
 * rowspan=3|(1/2+)
 * β+ (9.4%)
 * 257mLr
 * SF (1.3%)
 * (various)
 * rowspan=4 style="text-indent:1em" | 257m1Rf
 * rowspan=4 colspan="3" style="text-indent:2em" | 74 keV
 * rowspan=4|4.37(5) s
 * α (80.54%)
 * 253No
 * rowspan=4|(11/2-)
 * IT (14.2%)
 * 257Rf
 * β+ (4.86%)
 * 257Lr
 * SF (0.4%)
 * (various)
 * style="text-indent:1em" | 257m2Rf
 * colspan="3" style="text-indent:2em" | ~1125 keV
 * 134.9(77) μs
 * IT
 * 257m1Rf
 * (21/2, 23/2)
 * rowspan=2|258Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 154
 * rowspan=2|258.10343(3)
 * rowspan=2|12.5(5) ms
 * SF (95.1%)
 * (various)
 * rowspan=2|0+
 * α (4.9%)
 * 254No
 * style="text-indent:1em" | 258m1Rf
 * colspan="3" style="text-indent:2em" | 1200(300)# keV
 * IT
 * 258Rf
 * style="text-indent:1em" | 258m2Rf
 * colspan="3" style="text-indent:2em" | 1500(500)# keV
 * 15(10) μs
 * IT
 * 258m1Rf
 * rowspan=2|259Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 155
 * rowspan=2|259.10560(8)#
 * rowspan=2| 2.63(26) s
 * α (85%)
 * 255No
 * rowspan=2| 3/2+#
 * β+ (15%)
 * 259Lr
 * rowspan=2|260Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 156
 * rowspan=2|260.10644(22)#
 * rowspan=2|21(1) ms
 * SF
 * (various)
 * rowspan=2|0+
 * α (<20%)
 * 256No
 * rowspan=3|261Rf
 * rowspan=3 style="text-align:right" | 104
 * rowspan=3 style="text-align:right" | 157
 * rowspan=3|261.10877(5)
 * rowspan=3|75(7) s
 * α
 * 257No
 * rowspan=3|9/2+#
 * β+ (<14%)
 * 261Lr
 * SF (<11%)
 * (various)
 * rowspan=2 style="text-indent:1em" | 261mRf
 * rowspan=2 colspan="3" style="text-indent:2em" | 70(100)# keV
 * rowspan=2|1.9(4) s
 * SF (73%)
 * (various)
 * rowspan=2|3/2+#
 * α (27%)
 * 257No
 * 262Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 158
 * 262.10993(24)#
 * SF
 * (various)
 * 0+
 * style="text-indent:1em" | 262mRf
 * colspan="3" style="text-indent:2em" | 600(400)# keV
 * 47(5) ms
 * SF
 * (various)
 * high
 * rowspan=2|263Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 159
 * rowspan=2|263.1125(2)#
 * rowspan=2|11(3) min
 * SF (77%)
 * (various)
 * rowspan=2|3/2+#
 * α (23%)
 * 259No
 * style="text-indent:1em" | 263mRf
 * colspan="3" style="text-indent:2em" |
 * SF
 * (various)
 * 1/2#
 * 265Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 161
 * 265.11668(39)#
 * SF
 * (various)
 * 266Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 162
 * 266.11817(50)#
 * 23 s#
 * SF
 * (various)
 * 0+
 * 267Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 163
 * 267.12179(62)#
 * SF
 * (various)
 * 13/2−#
 * 268Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 164
 * 268.12397(77)#
 * 1.4 s#
 * SF
 * (various)
 * 0+
 * 270Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 166
 * 20 ms#
 * SF
 * (various)
 * 0+
 * (various)
 * high
 * rowspan=2|263Rf
 * rowspan=2 style="text-align:right" | 104
 * rowspan=2 style="text-align:right" | 159
 * rowspan=2|263.1125(2)#
 * rowspan=2|11(3) min
 * SF (77%)
 * (various)
 * rowspan=2|3/2+#
 * α (23%)
 * 259No
 * style="text-indent:1em" | 263mRf
 * colspan="3" style="text-indent:2em" |
 * SF
 * (various)
 * 1/2#
 * 265Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 161
 * 265.11668(39)#
 * SF
 * (various)
 * 266Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 162
 * 266.11817(50)#
 * 23 s#
 * SF
 * (various)
 * 0+
 * 267Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 163
 * 267.12179(62)#
 * SF
 * (various)
 * 13/2−#
 * 268Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 164
 * 268.12397(77)#
 * 1.4 s#
 * SF
 * (various)
 * 0+
 * 270Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 166
 * 20 ms#
 * SF
 * (various)
 * 0+
 * 1.4 s#
 * SF
 * (various)
 * 0+
 * 270Rf
 * style="text-align:right" | 104
 * style="text-align:right" | 166
 * 20 ms#
 * SF
 * (various)
 * 0+
 * (various)
 * 0+

Nucleosynthesis
Super-heavy elements such as rutherfordium are produced by bombarding lighter elements in particle accelerators that induces fusion reactions. Whereas most of the isotopes of rutherfordium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers.

Depending on the energies involved, the former are separated into "hot" and "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets (actinides), giving rise to compound nuclei at high excitation energy (~40–50 MeV) that may either fission or evaporate several (3 to 5) neutrons. In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20 MeV), which decreases the probability that these products will undergo fission reactions. As the fused nuclei cool to the ground state, they require emission of only one or two neutrons, and thus, allows for the generation of more neutron-rich products. The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).

Hot fusion studies
The synthesis of rutherfordium was first attempted in 1964 by the team at Dubna using the hot fusion reaction of neon-22 projectiles with plutonium-242 targets:
 * + →  + 3 or 5.

The first study produced evidence for a spontaneous fission with a 0.3 second half-life and another one at 8 seconds. While the former observation was eventually retracted, the latter eventually became associated with the 259Rf isotope. In 1966, the Soviet team repeated the experiment using a chemical study of volatile chloride products. They identified a volatile chloride with eka-hafnium properties that decayed fast through spontaneous fission. This gave strong evidence for the formation of RfCl4, and although a half-life was not accurately measured, later evidence suggested that the product was most likely 259Rf. The team repeated the experiment several times over the next few years, and in 1971, they revised the spontaneous fission half-life for the isotope at 4.5 seconds.

In 1969, researchers at the University of California led by Albert Ghiorso, tried to confirm the original results reported at Dubna. In a reaction of curium-248 with oxygen-16, they were unable to confirm the result of the Soviet team, but managed to observe the spontaneous fission of 260Rf with a very short half-life of 10–30 ms:
 * + →  + 4.

In 1970, the American team also studied the same reaction with oxygen-18 and identified 261Rf with a half-life of 65 seconds (later refined to 75 seconds). Later experiments at the Lawrence Berkeley National Laboratory in California also revealed the formation of a short-lived isomer of 262Rf (which undergoes spontaneous fission with a half-life of 47 ms), and spontaneous fission activities with long lifetimes tentatively assigned to 263Rf.

The reaction of californium-249 with carbon-13 was also investigated by the Ghiorso team, which indicated the formation of the short-lived 258Rf (which undergoes spontaneous fission in 11 ms):
 * + →  + 4.

In trying to confirm these results by using carbon-12 instead, they also observed the first alpha decays from 257Rf.

The reaction of berkelium-249 with nitrogen-14 was first studied in Dubna in 1977, and in 1985, researchers there confirmed the formation of the 260Rf isotope which quickly undergoes spontaneous fission in 28 ms:
 * + →  + 3.

In 1996 the isotope 262Rf was observed in LBNL from the fusion of plutonium-244 with neon-22:
 * + →  + 4 or 5.

The team determined a half-life of 2.1 seconds, in contrast to earlier reports of 47 ms and suggested that the two half-lives might be due to different isomeric states of 262Rf. Studies on the same reaction by a team at Dubna, lead to the observation in 2000 of alpha decays from 261Rf and spontaneous fissions of 261mRf.

The hot fusion reaction using a uranium target was first reported at Dubna in 2000:
 * + →  + x  (x = 3, 4, 5, 6).

They observed decays from 260Rf and 259Rf, and later for 259Rf. In 2006, as part of their program on the study of uranium targets in hot fusion reactions, the team at LBNL also observed 261Rf.

Cold fusion studies
The first cold fusion experiments involving element 104 were done in 1974 at Dubna, by using light titanium-50 nuclei aimed at lead-208 isotope targets:
 * + →  + x  (x = 1, 2, or 3).

The measurement of a spontaneous fission activity was assigned to 256Rf, while later studies done at the Gesellschaft für Schwerionenforschung Institute (GSI), also measured decay properties for the isotopes 257Rf, and 255Rf.

In 1974 researchers at Dubna investigated the reaction of lead-207 with titanium-50 to produce the isotope 255Rf. In a 1994 study at GSI using the lead-206 isotope, 255Rf as well as 254Rf were detected. 253Rf was similarly detected that year when lead-204 was used instead.

Decay studies
Most isotopes with an atomic mass below 262 have also observed as decay products of elements with a higher atomic number, allowing for refinement of their previously measured properties. Heavier isotopes of rutherfordium have only been observed as decay products. For example, a few alpha decay events terminating in 267Rf were observed in the decay chain of darmstadtium-279 since 2004:

This further underwent spontaneous fission with a half-life of about 1.3 h.

Investigations on the synthesis of the dubnium-263 isotope in 1999 at the University of Bern revealed events consistent with electron capture to form 263Rf. A rutherfordium fraction was separated, and several spontaneous fission events with long half-lives of about 15 minutes were observed, as well as alpha decays with half-lives of about 10 minutes. Reports on the decay chain of flerovium-285 in 2010 showed five sequential alpha decays that terminate in 265Rf, which further undergoes spontaneous fission with a half-life of 152 seconds.

Some experimental evidence was obtained in 2004 for a heavier isotope, 268Rf, in the decay chain of an isotope of moscovium:

However, the last step in this chain was uncertain. After observing the five alpha decay events that generate dubnium-268, spontaneous fission events were observed with a long half-life. It is unclear whether these events were due to direct spontaneous fission of 268Db, or 268Db produced electron capture events with long half-lives to generate 268Rf. If the latter is produced and decays with a short half-life, the two possibilities cannot be distinguished. Given that the electron capture of 268Db cannot be detected, these spontaneous fission events may be due to 268Rf, in which case the half-life of this isotope cannot be extracted. A similar mechanism is proposed for the formation of the even heavier isotope 270Rf as a short-lived daughter of 270Db (in the decay chain of 294Ts, first synthesized in 2010) which then undergoes spontaneous fission:

According to a 2007 report on the synthesis of nihonium, the isotope 282Nh was twice observed to undergo a similar decay to form 266Db. In one case this underwent spontaneous fission with a half-life of 22 minutes. Given that the electron capture of 266Db cannot be detected, these spontaneous fission events may be due to 266Rf, in which case the half-life of this isotope cannot be extracted. In the other case, no spontaneous fission event was observed; it could have been missed, or 266Db might have undergone two more alpha decays to long-lived 258Md, with a half-life (51.5 d) longer than the total time of the experiment.

Nuclear isomerism

Several early studies on the synthesis of 263Rf have indicated that this nuclide decays primarily by spontaneous fission with a half-life of 10–20 minutes. More recently, a study of hassium isotopes allowed the synthesis of atoms of 263Rf decaying with a shorter half-life of 8 seconds. These two different decay modes must be associated with two isomeric states, but specific assignments are difficult due to the low number of observed events.

During research on the synthesis of rutherfordium isotopes utilizing the 244Pu(22Ne,5n)261Rf reaction, the product was found to undergo exclusive 8.28 MeV alpha decay with a half-life of 78 seconds. Later studies at GSI on the synthesis of copernicium and hassium isotopes produced conflicting data, as 261Rf produced in the decay chain was found to undergo 8.52 MeV alpha decay with a half-life of 4 seconds. Later results indicated a predominant fission branch. These contradictions led to some doubt on the discovery of copernicium. The first isomer is currently denoted 261aRf (or simply 261Rf) whilst the second is denoted 261bRf (or 261mRf). However, it is thought that the first nucleus belongs to a high-spin ground state and the latter to a low-spin metastable state. The discovery and confirmation of 261bRf provided proof for the discovery of copernicium in 1996.

A detailed spectroscopic study of the production of 257Rf nuclei using the reaction 208Pb(50Ti,n)257Rf allowed the identification of an isomeric level in 257Rf. The work confirmed that 257gRf has a complex spectrum with 15 alpha lines. A level structure diagram was calculated for both isomers. Similar isomers were reported for 256Rf also.

Cold fusion
The table below provides cross-sections and excitation energies for cold fusion reactions producing rutherfordium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Hot fusion
The table below provides cross-sections and excitation energies for hot fusion reactions producing rutherfordium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

title: Isotopes of rutherfordium


text:
Isotopes of dubnium

Dubnium (105Db) is a synthetic element, thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 261Db in 1968. Thirteen radioisotopes are known, ranging from 255Db to 270Db (except 264Db, 265Db, and 269Db), along with one isomer (257mDb); two more isomers have been reported but are unconfirmed. The longest-lived known isotope is 268Db with a half-life of 16 hours.

List of isotopes
[$37 ms$] [$1.6 s$]
 * rowspan=2|255Db
 * rowspan=2 style="text-align:right" | 105
 * rowspan=2 style="text-align:right" | 150
 * rowspan=2|255.10707(45)#
 * rowspan=2|$19 s$
 * α (~50%)
 * 251Lr
 * rowspan=2|
 * SF (~50%)
 * (various)
 * rowspan=3|256Db
 * rowspan=3 style="text-align:right" | 105
 * rowspan=3 style="text-align:right" | 151
 * rowspan=3|256.10789(26)#
 * rowspan=3|1.7(4) s
 * rowspan=3 style="text-align:right" | 151
 * rowspan=3|256.10789(26)#
 * rowspan=3|1.7(4) s
 * α (70%)
 * 252Lr
 * rowspan=3|
 * β+ (30%)
 * 256Rf
 * SF (rare)
 * (various)
 * rowspan=3|257Db
 * rowspan=3 style="text-align:right" | 105
 * rowspan=3 style="text-align:right" | 152
 * rowspan=3|257.10758(22)#
 * rowspan=3|2.32(16) s
 * α (>92%)
 * 253Lr
 * rowspan=3|(9/2+)
 * SF (≤5%)
 * (various)
 * β+ (<3%)
 * 257Rf
 * rowspan=3 style="text-indent:1em" | 257mDb
 * rowspan=3 colspan="3" style="text-indent:2em" | 140(110)# keV
 * rowspan=3|0.67(7) s
 * α (>85%)
 * 253Lr
 * rowspan=3|(1/2−)
 * SF (≤12%)
 * (various)
 * β+ (<3%)
 * 257Rf
 * rowspan=2|258Db
 * rowspan=2 style="text-align:right" | 105
 * rowspan=2 style="text-align:right" | 153
 * rowspan=2|258.10929(33)#
 * rowspan=2|2.17(36) s
 * α (64%)
 * 254Lr
 * rowspan=2|(0-)
 * β+ (36%)
 * 258Rf
 * rowspan=2 style="text-indent:1em" | 258mDb
 * rowspan=2 colspan="3" style="text-indent:2em" | 51 keV
 * rowspan=2|4.41(21) s
 * α (77%)
 * 258Rf
 * rowspan=2|(5+,10−)
 * β+ (23%)
 * 258Db
 * 259Db
 * style="text-align:right" | 105
 * style="text-align:right" | 154
 * 259.10949(6)
 * 0.51(16) s
 * α
 * 255Lr
 * 9/2+#
 * rowspan=3|260Db
 * rowspan=3 style="text-align:right" | 105
 * rowspan=3 style="text-align:right" | 155
 * rowspan=3|260.1113(1)#
 * rowspan=3|1.52(13) s
 * α (90.4%)
 * 256Lr
 * rowspan=3|
 * SF (9.6%)
 * (various)
 * β+ (<2.5%)
 * 260Rf
 * style="text-indent:1em" | 260mDb
 * colspan="3" style="text-indent:2em" | 200(150)# keV
 * α
 * 256Lr
 * rowspan=2|261Db
 * rowspan=2 style="text-align:right" | 105
 * rowspan=2 style="text-align:right" | 156
 * rowspan=2|261.11192(12)#
 * rowspan=2|$4.1 s$
 * SF (73%)
 * (various)
 * rowspan=2|9/2+#
 * α (27%)
 * 257Lr
 * rowspan=2|262Db
 * rowspan=2 style="text-align:right" | 105
 * rowspan=2 style="text-align:right" | 157
 * rowspan=2|262.11407(15)#
 * rowspan=2|$33.8 s$
 * SF(β+?) (52%)
 * (various)
 * rowspan=2|
 * α (48%)
 * 258Lr
 * rowspan=3|263Db
 * rowspan=3 style="text-align:right" | 105
 * rowspan=3 style="text-align:right" | 158
 * rowspan=3|263.11499(18)#
 * rowspan=3|29(9) s
 * SF (73%)
 * (various)
 * rowspan=2|9/2+#
 * α (27%)
 * 257Lr
 * rowspan=2|262Db
 * rowspan=2 style="text-align:right" | 105
 * rowspan=2 style="text-align:right" | 157
 * rowspan=2|262.11407(15)#
 * rowspan=2|$27 s$
 * SF(β+?) (52%)
 * (various)
 * rowspan=2|
 * α (48%)
 * 258Lr
 * rowspan=3|263Db
 * rowspan=3 style="text-align:right" | 105
 * rowspan=3 style="text-align:right" | 158
 * rowspan=3|263.11499(18)#
 * rowspan=3|29(9) s
 * rowspan=3 style="text-align:right" | 105
 * rowspan=3 style="text-align:right" | 158
 * rowspan=3|263.11499(18)#
 * rowspan=3|29(9) s
 * SF (~56%)
 * (various)
 * rowspan=3|
 * α (~37%)
 * 259Lr
 * β+ (~6.9%)
 * 263Rf
 * rowspan=2|266Db
 * rowspan=2 style="text-align:right" | 105
 * rowspan=2 style="text-align:right" | 161
 * rowspan=2|266.12103(30)#
 * rowspan=2|$11 min$
 * SF
 * (various)
 * rowspan=2|
 * EC?
 * 266Rf
 * rowspan=2|267Db
 * rowspan=2 style="text-align:right" | 105
 * rowspan=2 style="text-align:right" | 162
 * rowspan=2|267.12247(44)#
 * rowspan=2|$1.4 h$
 * SF
 * (various)
 * rowspan=2|
 * EC?
 * 267Rf
 * rowspan=3|268Db
 * rowspan=3 style="text-align:right" | 105
 * rowspan=3 style="text-align:right" | 163
 * rowspan=3|268.12567(57)#
 * rowspan=3|$16 h$
 * α (51%)
 * 264Lr
 * rowspan=3|
 * SF (49%)
 * (various)
 * EC?
 * 268Rf
 * rowspan="3" | 270Db
 * rowspan="3" style="text-align:right" | 105
 * rowspan="3" style="text-align:right" | 165
 * rowspan="3" | 270.13136(64)#
 * rowspan="3" | $1 h$
 * α (~83%)
 * 266Lr
 * rowspan="3" |
 * SF (~17%)
 * (various)
 * EC?
 * 270Rf
 * rowspan="3" style="text-align:right" | 165
 * rowspan="3" | 270.13136(64)#
 * rowspan="3" | ⇭⇭⇭
 * α (~83%)
 * 266Lr
 * rowspan="3" |
 * SF (~17%)
 * (various)
 * EC?
 * 270Rf
 * EC?
 * 270Rf

Cold fusion
''This section deals with the synthesis of nuclei of dubnium by so-called "cold" fusion reactions. These are processes which create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only.''

The first attempts to synthesise dubnium using cold fusion reactions were performed in 1976 by the team at FLNR, Dubna using the above reaction. They were able to detect a 5 s spontaneous fission (SF) activity which they assigned to 257Db. This assignment was later corrected to 258Db. In 1981, the team at GSI studied this reaction using the improved technique of correlation of genetic parent-daughter decays. They were able to positively identify258Db, the product from the 1n neutron evaporation channel. In 1983, the team at Dubna revisited the reaction using the method of identification of a descendant using chemical separation. They succeeded in measuring alpha decays from known descendants of the decay chain beginning with 258Db. This was taken as providing some evidence for the formation of dubnium nuclei. The team at GSI revisited the reaction in 1985 and were able to detect 10 atoms of 257Db. After a significant upgrade of their facilities in 1993, in 2000 the team measured 120 decays of 257Db, 16 decays of 256Db and decay of258Db in the measurement of the 1n, 2n and 3n excitation functions. The data gathered for 257Db allowed a first spectroscopic study of this isotope and identified an isomer, 257mDb, and a first determination of a decay level structure for 257Db. The reaction was used in spectroscopic studies of isotopes of mendelevium and einsteinium in 2003–2004.
 * 209Bi(50Ti,xn)259−xDb (x=1,2,3)

This reaction was studied by Yuri Oganessian and the team at Dubna in 1983. They observed a 2.6 s SF activity tentatively assigned to 256Db. Later results suggest a possible reassignment to 256Rf, resulting from the ~30% EC branch in 256Db.
 * 209Bi(49Ti,xn)258−xDb (x=2?)

This reaction was studied by Yuri Oganessian and the team at Dubna in 1983. They observed a 1.6 s activity with a ~80% alpha branch with a ~20% SF branch. The activity was tentatively assigned to 255Db. Later results suggest a reassignment to 256Db. In 2005, the team at the University of Jyväskylä studied this reaction. They observed three atoms of 255Db with a cross section of 40 pb.
 * 209Bi(48Ti,xn)257−xDb (x=1?,2)

The team at Dubna also studied this reaction in 1976 and were again able to detect the 5 s SF activity, first tentatively assigned to 257Db and later to258Db. In 2006, the team at LBNL reinvestigated this reaction as part of their odd-Z projectile program. They were able to detect 258Db and 257Db in their measurement of the 1n and 2n neutron evaporation channels.
 * 208Pb(51V,xn)259−xDb (x=1,2)

The team at Dubna also studied this reaction in 1976 but this time they were unable to detect the 5 s SF activity, first tentatively assigned to 257Db and later to 258Db. Instead, they were able to measure a 1.5 s SF activity, tentatively assigned to 255Db.
 * 207Pb(51V,xn)258−xDb

The team at Dubna also studied this reaction in 1976 and were again able to detect the 5 s SF activity, first tentatively assigned to 257Db and later to 258Db.
 * 205Tl(54Cr,xn)259−xDb (x=1?)

Hot fusion
''This section deals with the synthesis of nuclei of dubnium by so-called "hot" fusion reactions. These are processes which create compound nuclei at high excitation energy (~40–50 MeV, hence "hot"), leading to a reduced probability of survival from fission and quasi-fission. The excited nucleus then decays to the ground state via the emission of 3–5 neutrons.''

There are very limited reports that this reaction using a phosphorus-31 beam was studied in 1989 by Andreyev et al. at the FLNR. One source suggests that no atoms were detected whilst a better source from the Russians themselves indicates that 258Db was synthesised in the 5n channel with a yield of 120 pb.
 * 232Th(31P,xn)263−xDb (x=5)

In 2006, as part of their study of the use of uranium targets in superheavy element synthesis, the LBNL team led by Ken Gregorich studied the excitation functions for the 4n and 5n channels in this new reaction.
 * 238U(27Al,xn)265−xDb (x=4,5)

This reaction was first studied by Andreyev et al. at the FLNR, Dubna in 1992. They were able to observe 258Db and 257Db in the 5n and 6n exit channels with yields of 450 pb and 75 pb, respectively.
 * 236U(27Al,xn)263−xDb (x=5,6)

The first attempts to synthesis dubnium were performed in 1968 by the team at the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna, Russia. They observed two alpha lines which they tentatively assigned to 261Db and 260Db. They repeated their experiment in 1970 looking for spontaneous fission. They found a 2.2 s SF activity which they assigned to 261Db. In 1970, the Dubna team began work on using gradient thermochromatography in order to detect dubnium in chemical experiments as a volatile chloride. In their first run they detected a volatile SF activity with similar adsorption properties to NbCl5 and unlike HfCl4. This was taken to indicate the formation of nuclei of dvi-niobium as DbCl5. In 1971, they repeated the chemistry experiment using higher sensitivity and observed alpha decays from an dvi-niobium component, taken to confirm the formation of 260105. The method was repeated in 1976 using the formation of bromides and obtained almost identical results, indicating the formation of a volatile, dvi-niobium-like DbBr5.
 * 243Am(22Ne,xn)265−xDb (x=5)

In 2000, Chinese scientists at the Institute of Modern Physics (IMP), Lanzhou, announced the discovery of the previously unknown isotope 259Db formed in the 4n neutron evaporation channel. They were also able to confirm the decay properties for 258Db.
 * 241Am(22Ne,xn)263−xDb (x=4,5)

This reaction was first studied in 1999 at the Paul Scherrer Institute (PSI) in order to produce 262Db for chemical studies. Just 4 atoms were detected with a cross section of 260 pb. Japanese scientists at JAERI studied the reaction further in 2002 and determined yields for the isotope 262Db during their efforts to study the aqueous chemistry of dubnium.
 * 248Cm(19F,xn)267−xDb (x=4,5)

Following from the discovery of 260Db by Albert Ghiorso in 1970 at the University of California (UC), the same team continued in 1971 with the discovery of the new isotope 262Db. They also observed an unassigned 25 s SF activity, probably associated with the now-known SF branch of 263Db. In 1990, a team led by Kratz at LBNL definitively discovered the new isotope 263Db in the 4n neutron evaporation channel. This reaction has been used by the same team on several occasions in order to attempt to confirm an electron capture (EC) branch in 263Db leading to long-lived 263Rf (see rutherfordium).
 * 249Bk(18O,xn)267−xDb (x=4,5)

Following from the discovery of 260Db by Albert Ghiorso in 1970 at the University of California (UC), the same team continued in 1971 with the discovery of the new isotope 261Db.
 * 249Bk(16O,xn)265−xDb (x=4)

Following from the discovery of 260Db by Ghiorso in 1970 at LBNL, the same team continued in 1971 with the discovery of the new isotope 261Db.
 * 250Cf(15N,xn)265−xDb (x=4)

In 1970, the team at the Lawrence Berkeley National Laboratory (LBNL) studied this reaction and identified the isotope 260Db in their discovery experiment. They used the modern technique of correlation of genetic parent-daughter decays to confirm their assignment. In 1977, the team at Oak Ridge repeated the experiment and were able to confirm the discovery by the identification of K X-rays from the daughter lawrencium.
 * 249Cf(15N,xn)264−xDb (x=4)

In 1988, scientists as the Lawrence Livermore National Laboratory (LLNL) used the asymmetric hot fusion reaction with an einsteinium-254 target to search for the new nuclides 264Db and 263Db. Due to the low sensitivity of the experiment caused by the small 254Es target, they were unable to detect any evaporation residues (ER).
 * 254Es(13C,xn)267−xDb

Decay of heavier nuclides
Isotopes of dubnium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:

260Db
Recent data on the decay of 272Rg has revealed that some decay chains continue through 260Db with extraordinary longer life-times than expected. These decays have been linked to an isomeric level decaying by alpha decay with a half-life of ~19 s. Further research is required to allow a definite assignment.

258Db
Evidence for an isomeric state in 258Db has been gathered from the study of the decay of 266Mt and 262Bh. It has been noted that those decays assigned to an electron capture (EC) branch has a significantly different half-life to those decaying by alpha emission. This has been taken to suggest the existence of an isomeric state decaying by EC with a half-life of ~20 s. Further experiments are required to confirm this assignment.

257Db
A study of the formation and decay of 257Db has proved the existence of an isomeric state. Initially, 257Db was taken to decay by alpha emission with energies 9.16, 9.07 and 8.97 MeV. A measurement of the correlations of these decays with those of 253Lr have shown that the 9.16 MeV decay belongs to a separate isomer. Analysis of the data in conjunction with theory have assigned this activity to a meta stable state, 257mDb. The ground state decays by alpha emission with energies 9.07 and 8.97 MeV. Spontaneous fission of 257m,gDb was not confirmed in recent experiments.

Cold fusion
The table below provides cross-sections and excitation energies for cold fusion reactions producing dubnium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Hot fusion
The table below provides cross-sections and excitation energies for hot fusion reactions producing dubnium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

title: Isotopes of dubnium


text:
Wikipedia:Requests for comment/Fenian Swine

Even though the User claims to be a Fenian, the name itself is an attack, and should not be allowed. Zoe 23:58, August 20, 2005 (UTC)

 * Considering the name to be "an attack" is your POV. This is a spurious listing.  Have you advised the user of this listing on his talk page Zoe, in accordance with guidance listed above?  I didn't think so.  Best go do it now so the 'defendant' can be heard. --84.66.120.77 07:23, 23 August 2005 (UTC)

 * Too late, I've done it for you --84.68.18.21 15:48, 23 August 2005 (UTC)

See also: Comments on WP:AN. --84.68.18.21 15:57, 23 August 2005 (UTC)

I am concerned about this user's behavior. Not only the negative response to several requests to change the name, which does appear inappropriate, but other behaviour as well. He nominated a user with fewer than fifty edits for admin. When I posted a polite question asking why, he gave a short reply, but not in English. This is not from an inability to use English but it appears more a refusal to respond to requests and questions. Jonathunder 16:03, 2005 August 23 (UTC)

 * He responded in Irish which, though kinda rude when addressed in English, somewhat corresponds to the Fenian image. Dunno why he uses the name myself - it's a bit juvenile - but he probably means no harm. - Pete C ✍ 17:34, 23 August 2005 (UTC)

 * Ok, so I checked what he said here, and it was Tá brón orm faoi seo, which simply means, "I'm sorry about this". Just FYI - Pete C ✍ 18:34, 23 August 2005 (UTC)

 * Thank you for the translation, Pete C. That helps. Jonathunder 19:40, 2005 August 23 (UTC)

 * Again as I have already said to user:zoe,have the common courtesy to inform me about this discussion and don't have it behind my back.Name means no harm.Get over it.Go raibh míle.--Fenian Swine 23:35, 23 August 2005 (UTC)

Sorry, "get over it" doesn't cut it. Your name is offensive. Change it. Period. Zoe 23:54, August 23, 2005 (UTC)

In other words-administrator abusing power,again.I will not change it.I assume your American.--Fenian Swine 00:03, 24 August 2005 (UTC)

 * People from more than one nation have advised you to change the name, F.S. Not that one's nationality has any bearing on the matter that I can see. Frankly, I'm not as concerned about your user name as I am about the tone of your responses. Please be polite and assume good faith. You'll be much more likely to get a positive response from others. Jonathunder 00:14, 2005 August 24 (UTC)

I have not been shown respect eg ''Your name is offensive. Change it. Period.'' by who else but Zoe.In other words she is unwilling to listen to my argument.Also this argument was started behind my back and I only found out about it through an anonimous user.That shows a huge lack of respest and I'm only willing to show zoe respect when she shoes it to me.signed serious editor --Fenian Swine 00:20, 24 August 2005 (UTC)

 * Can we open a subpage for this argument, please? Some of us have this page watchlisted.  Robert McClenon 00:23, 24 August 2005 (UTC)

 * Fenian Swine doesn't read like an "attack" to me. On the chance that it might be some set-phrase slur, however, I googled it, and it's not. It appears to be an allusion to the movie Michael Collins, in which it was part of a throw-away self-reference, not a term of ethnic abuse. A little context goes a long way. If the same name were adopted by an anti-Irish bigot, of course, the bigotry itself would be grounds for action. Unless there's a blanket policy against irreverence, therefore, the name doesn't seem to rise to the level of offensive. Seems pretty tame actually. In conclusion, I would ban the swine for his semiliterate American-bashing instead. Cheers. Squib 00:30, 24 August 2005 (UTC)

America bashing.I must be missing something huge here.When did I bash america.--Fenian Swine 00:34, 24 August 2005 (UTC)
 * Maybe I misperceived an association between your charge of abuse of power and your connected comment, "I assume your American." (Though I wasn't being entirely serious in any event.) Squib 00:42, 24 August 2005 (UTC)
 * No I just wanted to see if she was a Fenian or whether she was American.--Fenian Swine 00:57, 24 August 2005 (UTC)
 * Because after all, there are only two types of people in the word: Fenians and Americans. Acetic Acid 06:59, August 24, 2005 (UTC)
 * Yes .--Play Brian Moore 00:34, 26 August 2005 (UTC)

I see that Zoe has unilaterally blocked this user name. There is no concensus here for that action, nor one at WP:AN. I request, therefore, that A.N.Other admin unblocks this user name until a concensus is reached. --81.79.249.207 07:49, 24 August 2005 (UTC)

If someone is this offended, just change the name. The idea of a wiki is that everyone gets on. If you're really upsetting someone, stop doing it. Sometimes I have to remind myself that we are at least pretending to be here to build an encyclopaedia. The user name is calculated to offend. It offended. Well done. Now you've snared a hotheaded admin and can bait her. Double well done. Zoe, you've done the right thing, now I hope you'll walk away and not feed the fire any more. Clair de Lune 07:54, 24 August 2005 (UTC)

 * Exactly my point - "a hotheaded admin" - who is going to take action against this so called hot head? Which admin is big enough to restore this user name until there is concensus? Why should Fenian Swine be forced to change his user name on the whim of a "hotheaded admin's" POV.  As a result, he cannot participate in this discussion, how ridiculous is that? You also seem to be labouring under the misapprehension that I am Fenian Swine.  I hate to disappoint you, but I am not. --81.79.249.207 08:29, 24 August 2005 (UTC)

On a tangent, and I'm British by the way. If it was 'Fenian Scum' it would definitely be offensive; but 'Swine' has an archaic feel to it, and if someone is using it to describe themselves it seems harmless enough, albeit that passions run high in this field. ('Proddy Bastard' would be beyond the pale.) The problem is that the kind of text-based communication used on Wikipedia doesn't leave any room for nuance, irony or tone; and of course neither us nor any other Wikipedia editor knows Mr Swine as a person.

As for his concerns regarding people going behind his back, I often worry that Wikipedia's rules-bashing goes on out of sight of everyday users, and that one day I will find myself banned for violating a recently-introduced clause at one of Wikipedia's many ever-changing policy sub-pages, just as notification of Arthur Dent's house demolition was posted in an inaccessible, obscure location. I can understand why a new user might be angry at strangers judging him and discussing his fate behind the curtain; although there is a clear warning that new users should choose inoffensive usernames, there's nothing in the standard Wikipedia welcome message that suggests users should frequently check the Requests for Comment section. Where are the real decisions made? IRC? E-mail?

I believe that ''Your name is offensive. Change it. Period.'' is pretty poor form for anyone, certainly an admin on Wikipedia. This isn't Les Miserables. We aren't deliberately trying to root out the evildoers by provocing them, much as we might like to. Judging by her talk page, Zoe has been around for a long time; I have been in that situation myself, and I didn't like the kind of person I became.

Mr Swine's subsequent actions have damaged his position already, and this affair is not a shining example of anything. "Well, who the hell asked you?".-Ashley Pomeroy 11:04, 24 August 2005 (UTC)
 * What is this in relation to ie "Well, who the hell asked you?".--Muc Fíníneach 14:29, 24 August 2005 (UTC)

 * Stop blaspheming me --Mr Swine 16:44, 24 August 2005 (UTC)

I wonder why there was a request for comment made in the first place. Could have saved a lot of time. Squib 18:07, 24 August 2005 (UTC)
 * I agree l r.--Muc Fíníneach 22:26, 24 August 2005 (UTC)

 * Shining example of stage Irishmanship and sockpuppetry, maybe. Please see the latest on WP:AN. Bishonen | talk 22:23, 26 August 2005 (UTC)

Swines, eh?
Oink oink oink oink oink oink oink oink oink oink oink. — Rickyrab | Talk 03:58, 30 August 2005 (UTC)


text:
Tanaquil Le Clercq

Tanaquil Le Clercq (October 2, 1929 – December 31, 2000) was an American ballet dancer, born in Paris, France, who became a principal dancer with the New York City Ballet at the age of nineteen. Her dancing career ended abruptly when she was stricken with polio in Copenhagen during the company's European tour in 1956. Eventually regaining most of the use of her arms and torso, she remained paralyzed from the waist down for the rest of her life.

Biography
Le Clercq was the daughter of Jacques Georges Clemenceau Le Clercq, a European American intellectual, professor of French at Queens College in the 1950s-early 1970s, and his American wife, Edith (née Whittemore), who were married on June 28, 1928. Tanaquil studied ballet with Mikhail Mordkin before auditioning for the School of American Ballet in 1941, where she won a scholarship.

When Le Clercq was fifteen years old, famed choreographer George Balanchine asked her to perform with him in a dance he choreographed for a polio charity benefit. In an eerie portent of things to come, he played a character named Polio, and Le Clercq was his victim who became paralyzed and fell to the floor. Then, children tossed dimes at her character, prompting her to get up and dance again. She was considered Balanchine's first ballerina: she was trained in his style from childhood and she was one of his most important muses, together with dancers like Maria Tallchief and, later on, Suzanne Farrell. During Le Clercq's tenure with the company, Balanchine, Jerome Robbins, and Merce Cunningham all created roles for her. Le Clercq became a principal dancer with the New York City Ballet at the age of nineteen. Her dancing career ended abruptly when she was stricken with polio in Copenhagen during the company's European tour in 1956. Eventually regaining most of the use of her arms and torso, she remained paralyzed from the waist down for the rest of her life.

She reemerged as a dance teacher and as one student recalled, "used her hands and arms as legs and feet." She taught at Dance Theater of Harlem from 1974 to 1982.

Legacy
Le Clercq's life and career are profiled in the 2013 documentary film, Afternoon of a Faun: Tanaquil Le Clercq. Novelist Varley O'Connor created a fictional account of the relationship between Tanaquil LeClercq and George Balanchine in The Master's Muse (Scribner 2012).

Personal life
Tanaquil Le Clercq was the fourth and last wife (1952–1969) of George Balanchine, the pioneer of American ballet. He obtained a quick divorce from her to woo Suzanne Farrell (who refused Balanchine's marriage proposal and went on to marry another Balanchine dancer, Paul Mejia).

Le Clercq died of pneumonia in New York Hospital at the age of 71.

title: Tanaquil Le Clercq