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Isotopes of californium

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Actinides[1] by decay chain Half-life
range (a)
Fission products of 235U by yield[2]
4n 4n + 1 4n + 2 4n + 3 4.5–7% 0.04–1.25% <0.001%
228Ra 4–6 a 155Euþ
248Bk[3] > 9 a
244Cmƒ 241Puƒ 250Cf 227Ac 10–29 a 90Sr 85Kr 113mCdþ
232Uƒ 238Puƒ 243Cmƒ 29–97 a 137Cs 151Smþ 121mSn
249Cfƒ 242mAmƒ 141–351 a

No fission products have a half-life
in the range of 100 a–210 ka ...

241Amƒ 251Cfƒ[4] 430–900 a
226Ra 247Bk 1.3–1.6 ka
240Pu 229Th 246Cmƒ 243Amƒ 4.7–7.4 ka
245Cmƒ 250Cm 8.3–8.5 ka
239Puƒ 24.1 ka
230Th 231Pa 32–76 ka
236Npƒ 233Uƒ 234U 150–250 ka 99Tc 126Sn
248Cm 242Pu 327–375 ka 79Se
1.33 Ma 135Cs
237Npƒ 1.61–6.5 Ma 93Zr 107Pd
236U 247Cmƒ 15–24 Ma 129I
244Pu 80 Ma

... nor beyond 15.7 Ma[5]

232Th 238U 235Uƒ№ 0.7–14.1 Ga

Californium (Cf) has no stable isotopes. There are 20 known radioisotopes ranging from 237Cf to 256Cf and one nuclear isomer, 249mCf. A standard atomic mass cannot be given due to Californium being an artificial element. The isotope with the longest half-life is 251Cf with a half-life of 900 years.

Californium-252

Fission neutrons of californium-252 have an energy range of 0 to 13 MeV with a mean value of 2.3 MeV and a most probable value of 1 MeV.[6]

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[7][n 1]
daughter
isotope(s)
nuclear
spin
excitation energy
237Cf 98 139 237.06207(54)# 2.1(3) s SF (various) 5/2+#
β+ 237Bk
α 233Cm
238Cf 98 140 238.06141(43)# 21.1(13) ms SF (various) 0+
β+ (rare) 238Bk
α (rare) 234Cm
239Cf 98 141 239.06242(23)# 60(30) s
[39(+37-12) s]
α 235Cm 5/2+#
β+ (rare) 239Bk
240Cf 98 142 240.06230(22)# 1.06(15) min α (98%) 236Cm 0+
SF (2%) (various)
β+ (rare) 240Bk
241Cf 98 143 241.06373(27)# 3.78(70) min β+ (75%) 241Bk 7/2-#
α (25%) 237Cm
242Cf 98 144 242.06370(4) 3.49(15) min α (80%) 238Cm 0+
β+ (20%) 242Bk
SF (.014%) (various)
243Cf 98 145 243.06543(15)# 10.7(5) min β+ (86%) 243Bk (1/2+)
α (14%) 239Cm
244Cf 98 146 244.066001(3) 19.4(6) min α (99%) 240Cm 0+
EC (1%) 244Bk
245Cf 98 147 245.068049(3) 45.0(15) min β+ (64%) 245Bk (5/2+)
α (36%) 241Cm
246Cf 98 148 246.0688053(22) 35.7(5) h α 242Cm 0+
EC (5E-4%) 246Bk
SF (2E-4%) (various)
247Cf 98 149 247.071001(9) 3.11(3) h EC (99.96%) 247Bk (7/2+)#
α (.04%) 243Cm
248Cf 98 150 248.072185(6) 333.5(28) d α (99.99%) 244Cm 0+
SF (.0029%) (various)
249Cf 98 151 249.0748535(24) 351(2) a α 245Cm 9/2-
SF (5E-7%) (various)
249mCf 144.98(5) keV 45(5) µs 5/2+
250Cf 98 152 250.0764061(22) 13.08(9) a α (99.92%) 246Cm 0+
SF (.077%) (various)
251Cf[n 2] 98 153 251.079587(5) 900(40) a α 247Cm 1/2+
252Cf 98 154 252.081626(5) 2.645(8) a α (96.9%) 248Cm 0+
SF (3.09%)[n 3] (various)
253Cf 98 155 253.085133(7) 17.81(8) d β- (99.69%) 253Es (7/2+)
α (.31%) 249Cm
254Cf 98 156 254.087323(13) 60.5(2) d SF (99.69%) (various) 0+
α (.31%) 250Cm
β-β- (rare) 254Fm
255Cf 98 157 255.09105(22)# 85(18) min β- (99.99%) 255Es (7/2+)
SF (.001%) (various)
α (1E-5%) 251Cm
256Cf 98 158 256.09344(32)# 12.3(12) min SF (99%) (various) 0+
β- (1%) 256Es
α (1E-6%) 252Cm
β-β- (rare) 256Fm
  1. ^ Abbreviations:
    EC: Electron capture
    SF: Spontaneous fission
  2. ^ High neutron cross-section, tends to absorb neutrons
  3. ^ High neutron emitter, average 3.7 neutrons per fission

Notes

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

  • Isotope masses from:
    • G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. doi:10.1016/j.nuclphysa.2003.11.001.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  • Isotopic compositions and standard atomic masses from:
  • Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • Other
  1. ^ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
  2. ^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
  3. ^ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
    "The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk248 with a half-life greater than 9 [years]. No growth of Cf248 was detected, and a lower limit for the β half-life can be set at about 104 [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
  4. ^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
  5. ^ Excluding those "classically stable" nuclides with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is eight quadrillion years.
  6. ^ Dicello, J. F. (1972). "Radiation Quality of Californium-252". Physics in Medicine and Biology. 17 (3): 345. doi:10.1088/0031-9155/17/3/301. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  7. ^ http://www.nucleonica.net/unc.aspx