Difference between revisions of "Isotopes of fermium"

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Revision as of 16:20, 24 September 2010

Fermium is an artificial element, and has no stable or naturally occuring isotopes. The first isotope to be discovered was 255100Fm, in fallout from the first test of a hydrogen bomb, codenamed 'Ivy Mike', in 1952. 250100Fm was discovered independently in 1954.

Symbol Z(p) N(n) Mass/u Excess energy
MeV
Binding energy/A
MeV
β-decay energy
MeV
Spin Half life Decay mode,
proportion
Excitation energy/MeV
242Fm 100 142 242.073 43(43)# 68 400(401)# 7465(2)# 0 0.8(2) ms SF (? %); α (? %)
243Fm 100 143 69260(220)# 72# 210(60) ms α;[Note 1] β+ (? %); SF (59%#)
244Fm 100 144 69010(280) 0 3.3(0.5) ms SF (≈100%); α (0.4%#)
245Fm 100 145 70220(280)# +½# 4.2(13) s α (? %); β+ (4.2%#); SF (0.13%#)
Values marked # are estimated from systematic trends rather than experimentally measured.
Spins quoted in parentheses are uncertain in value and/or parity.
Sources: Except as otherwise noted,
isotopic masses and associated energies are taken from the AME 2003 dataset;[1]
nuclear spins and decay properties are taken from NUBASE 2003.[2]

Notes and references

Notes

  1. The α ranching ratio depends on the uncertain branching ratio of the daughter 239Cf.

References

  1. Wapstra, A. H.; Audi, G.; Thibault, C. The AME2003 atomic mass evaluation (I). Evaluation of input data, adjustment procedures. Nucl. Phys. A 2003, 729, 129–336. DOI: 10.1016/j.nuclphysa.2003.11.002. Wapstra, A. H.; Audi, G.; Thibault, C. The AME2003 atomic mass evaluation (II). Tables, graphs, and references. Nucl. Phys. A 2003, 729, 337–676. DOI: 10.1016/j.nuclphysa.2003.11.003. Data tables.
  2. Audi, G.; Bersillon, O.; Blachot, J.; Wapstra, A. H. The NUBASE evaluation of nuclear and decay properties. Nucl. Phys. A 2003, 729, 3–128. doi:10.1016/j.nuclphysa.2003.11.001, <http://amdc.in2p3.fr/nubase/Nubase2003.pdf>.
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