Isotopes of curium

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Isotopes of curium  (96Cm)
Main isotopes [1] Decay
abun­dance half-life (t1/2) mode pro­duct
242Cm synth 162.8 d α 238Pu
SF –
CD 208Pb
243Cmsynth29.1 yα 239Pu
ε 243Am
SF–
244Cmsynth18.11 yα 240Pu
SF–
245Cmsynth8250 yα 241Pu
SF–
246Cmsynth4760 yα 242Pu
SF–
247Cmsynth1.56×107 yα 243Pu
248Cmsynth3.480×105 yα 244Pu
SF–
250Cmsynth8300 ySF–
α 246Pu
β− 250Bk

Curium (96Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was 242Cm in 1944, which has 146 neutrons.

Contents

There are 19 known radioisotopes ranging from 233Cm to 251Cm. There are also ten known nuclear isomers. The longest-lived isotope is 247Cm, with half-life 15.6 million years – orders of magnitude longer than that of any known isotope beyond curium, and long enough to study as a possible extinct radionuclide that would be produced by the r-process. [2] [3] The longest-lived known isomer is 246mCm with a half-life of 1.12 seconds.

List of isotopes


Nuclide
[n 1] 		Z N Isotopic mass (Da) [4]
[n 2] [n 3] 		Half-life [1]
[n 4] 		Decay
mode [1]
[n 5] 		Daughter
isotope
Spin and
parity [1]
[n 6] [n 4]
Excitation energy [n 4]
233Cm96137233.050771(87)27(10) s β+ (80%)233Am3/2+#
α (20%)229Pu
234Cm96138234.050159(18)52(9) sβ+ (71%)234Am0+
α (27%)230Pu
SF (2%)(various)
235Cm96139235.05155(11)#7(3) minβ+ (96%)235Am5/2+#
α (4%)231Pu
236Cm96140236.051372(19)6.8(8) minβ+ (82%)236Am0+
α (18%)232Pu
237Cm96141237.052869(80)>10# minα (?%)233Pu5/2+#
238Cm96142238.053082(13)2.2(4) h EC (96.11%)238Am0+
α (3.84%)234Pu
SF (0.048%)(various)
239Cm96143239.05491(16)2.5(4) hβ+239Am7/2−#
α (6.2x10−3%)235Pu
240Cm96144240.0555282(20)30.4(37) dα236Pu0+
SF (3.9×10−6%)(various)
241Cm96145241.0576512(17)32.8(2) dEC (99.0%)241Am1/2+
α (1.0%)237Pu
242Cm96146242.0588342(12)162.8(2) dα [n 7] 238Pu0+
SF (6.2×10−6%)(various)
CD (1.1×10−14%) [n 8] 208Pb
34Si
242mCm2800(100) keV180(70) ns
243Cm96147243.0613873(16)29.1(1) yα (99.71%)239Pu5/2+
EC (0.29%)243Am
SF (5.3×10−9%)(various)
243mCm87.4(1) keV1.08(3) μs IT 243Cm1/2+
244Cm96148244.0627506(12)18.11(3) yα240Pu0+
SF (1.37×10−4%)(various)
244m1Cm1040.181(11) keV34(2) msIT244Cm6+
244m2Cm1100(900)# keV>500 nsSF(various)
245Cm96149245.0654910(12)8250(70) yα241Pu7/2+
SF (6.1×10−7%)(various)
245mCm355.92(10) keV290(20) nsIT245Cm1/2+
246Cm96150246.0672220(16)4706(40) yα (99.97%)242Pu0+
SF (0.02615%)(various
246mCm1179.66(13) keV1.12(24) sIT246Cm8−
247Cm96151247.0703527(41)1.56(5)×107 yα243Pu9/2−
247m1Cm227.38(19) keV26.3(3) μsIT247Cm5/2+
247m2Cm404.90(3) keV100.6(6) nsIT247Cm1/2+
248Cm96152248.0723491(25)3.48(6)×105 yα (91.61%) [n 9] 244Pu0+
SF (8.39%)(various)
248mCm1458.1(10) keV146(18) μsIT248Cm8−#
249Cm96153249.0759540(25)64.15(3) minβ−249Bk1/2+
249mCm48.76(4) keV23 μsα245Pu7/2+
250Cm96154250.078358(11)8300# ySF (74%) [n 10] (various)0+
α (?%)246Pu
β− (?%)250Bk
251Cm96155251.082285(24)16.8(2) minβ−251Bk(3/2+)
This table header & footer:
  1. ↑ mCm – Excited nuclear isomer.
  2. ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. 1 2 3 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. ↑ Modes of decay:
    CD: Cluster decay
    EC: Electron capture
    SF: Spontaneous fission
  6. ↑ ( ) spin value – Indicates spin with weak assignment arguments.
  7. ↑ Theoretically capable of β+β+ decay to 242Pu
  8. ↑ Heaviest known nuclide to undergo cluster decay
  9. ↑ Theoretically capable of β−β− decay to 248Cf
  10. ↑ The nuclide with the lowest atomic number known to undergo spontaneous fission as the main decay mode

Actinides vs fission products

Actinides and fission products by half-life
Actinides [5] by decay chain Half-life
range (a)		 Fission products of 235U by yield [6]
4n 4n + 1 4n + 2 4n + 3 4.5–7%0.04–1.25%<0.001%
228 Ra№ 4–6 a 155 Euþ
248 Bk [7] > 9 a
244 Cmƒ 241 Puƒ 250 Cf 227 Ac№ 10–29 a 90 Sr 85 Kr 113m Cdþ
232 Uƒ 238 Puƒ 243 Cmƒ 29–97 a 137 Cs 151 Smþ 121m Sn
249 Cfƒ 242m Amƒ141–351 a

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

241 Amƒ 251 Cfƒ [8] 430–900 a
226 Ra№ 247 Bk1.3–1.6 ka
240 Pu 229 Th 246 Cmƒ 243 Amƒ4.7–7.4 ka
245 Cmƒ 250 Cm8.3–8.5 ka
239 Puƒ24.1 ka
230 Th№ 231 Pa№32–76 ka
236 Npƒ 233 Uƒ 234 U№ 150–250 ka 99 Tc₡ 126 Sn
248 Cm 242 Pu 327–375 ka 79 Se₡
1.33 Ma 135 Cs₡
237 Npƒ 1.61–6.5 Ma 93 Zr 107 Pd
236 U 247 Cmƒ 15–24 Ma 129 I₡
244 Pu80 Ma

... nor beyond 15.7 Ma [9]

232 Th№ 238 U№ 235 Uƒ№0.7–14.1 Ga

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References

  1. 1 2 3 4 Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ↑ Côté, Benoit; Eichler, Marius; Yagüe López, Andrés; Vassh, Nicole; Mumpower, Matthew R.; Világos, Blanka; Soós, Benjámin; Arcones, Almudena; Sprouse, Trevor M.; Surman, Rebecca; Pignatari, Marco; Pető, Mária K.; Wehmeyer, Benjamin; Rauscher, Thomas; Lugaro, Maria (26 February 2021). "129I and 247Cm in meteorites constrain the last astrophysical source of solar r-process elements". Science. 371 (6532): 945–948. arXiv: 2006.04833 . Bibcode:2021Sci...371..945C. doi:10.1126/science.aba1111. PMID   33632846. S2CID   232050526.
  3. ↑ Davis, A.M.; McKeegan, K.D. (2014). "Short-Lived Radionuclides and Early Solar System Chronology". Treatise on Geochemistry: 383. doi:10.1016/B978-0-08-095975-7.00113-3. ISBN   9780080983004.
  4. ↑ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  5. ↑ 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.
  6. ↑ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
  7. ↑ 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]."
  8. ↑ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
  9. ↑ 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.
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