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Isotopes of curium

  (Redirected from Curium-243)

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.

Main isotopes of curium (96Cm)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
242Cm syn 160 d SF
α 238Pu
243Cm syn 29.1 y α 239Pu
ε 243Am
SF
244Cm syn 18.1 y SF
α 240Pu
245Cm syn 8500 y SF
α 241Pu
246Cm syn 4730 y α 242Pu
SF
247Cm syn 1.56×107 y α 243Pu
248Cm syn 3.40×105 y α 244Pu
SF
250Cm syn 9000 y SF
α 246Pu
β 250Bk

There are 19 known radioisotopes with atomic masses ranging from 233Cm to 251Cm. There are also ten known nuclear isomers. The longest-lived isotope is 247Cm, with a half-life of 15.6 million years – several orders of magnitude longer than the half-life of all known nuclei of elements beyond curium in the periodic table. The longest-lived isomer is 246mCm with a half-life of 1.12 seconds.

List of isotopesEdit

Nuclide
[n 1]
Z N Isotopic mass (u)
[n 2][n 3]
Half-life
[n 4]
Decay
mode

[n 5]
Daughter
isotope

Spin and
parity
[n 6][n 4]
Excitation energy[n 4]
233Cm 96 137 233.05077(8) 27(10) s β+ (80%) 233Am 3/2+#
α (20%) 229Pu
234Cm 96 138 234.05016(2) 52(9) s β+ (71%) 234Am 0+
α (27%) 230Pu
SF (2%) (various)
235Cm 96 139 235.05143(22)# 5# min β+ 235Am 5/2+#
α 231Pu
236Cm 96 140 236.05141(22)# 6.8(0.8) min β+ (82%) 236Am 0+
α (18%) 232Pu
237Cm 96 141 237.05290(22)# 20# min β+ 237Am 5/2+#
α 233Pu
238Cm 96 142 238.05303(4) 2.4(1) h EC (90%) 238Am 0+
α (10%) 234Pu
239Cm 96 143 239.05496(11)# 2.5(0.4) h β+ (99.9%) 239Am (7/2−)
α (.1%) 235Pu
240Cm 96 144 240.0555295(25) 27(1) d α (99.5%) 236Pu 0+
EC (.5%) 240Am
SF (3.9×10−6%) (various)
241Cm 96 145 241.0576530(23) 32.8(2) d EC (99%) 241Am 1/2+
α (1%) 237Pu
242Cm[n 7] 96 146 242.0588358(20) 162.8(2) d α 238Pu 0+
SF (6.33×10−6%) (various)
CD (10−14%)[n 8] 208Pb
34Si
β+β+ (rare) 242Pu
242mCm 2800(100) keV 180(70) ns
243Cm 96 147 243.0613891(22) 29.1(1) y α (99.71%) 239Pu 5/2+
EC (.29%) 243Am
SF (5.3×10−9%) (various)
243mCm 87.4(1) keV 1.08(3) µs IT 243Cm 1/2+
244Cm[n 7] 96 148 244.0627526(20) 18.10(2) y α 240Pu 0+
SF (1.34×10−4%) (various)
244m1Cm 1040.188(12) keV 34(2) ms IT 244Cm 6+
244m2Cm 1100(900)# keV >500 ns SF (various)
245Cm 96 149 245.0654912(22) 8.5(1)×103 y α 241Pu 7/2+
SF (6.1×10−7%) (various)
245mCm 355.92(10) keV 290(20) ns IT 245Cm 1/2+
246Cm 96 150 246.0672237(22) 4.76(4)×103 y α (99.97%) 242Pu 0+
SF (.0261%) (various)
246mCm 1179.66(13) keV 1.12(0.24) s IT 246Cm 8-
247Cm 96 151 247.070354(5) 1.56(5)×107 y α 243Pu 9/2−
247m1Cm 227.38(19) keV 26.3(0.3) µs IT 247Cm 5/2+
247m2Cm 404.90(3) keV 100.6(0.6) ns IT 247Cm 1/2+
248Cm 96 152 248.072349(5) 3.48(6)×105 y α (91.74%) 244Pu 0+
SF (8.26%) (various)
ββ (rare) 248Cf
248mCm 1458.1(1) keV 146(18) µs IT 248Cm (8-)
249Cm 96 153 249.075953(5) 64.15(3) min β 249Bk 1/2(+)
249mCm 48.758(17) keV 23 µs α 245Pu (7/2+)
250Cm 96 154 250.078357(12) 8300# y SF (74%)[n 9] (various) 0+
α (18%) 246Pu
β (8%) 250Bk
251Cm 96 155 251.082285(24) 16.8(2) min β 251Bk (1/2+)
  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. ^ a b c # – 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. ^ a b Most common isotopes
  8. ^ Heaviest known nuclide to undergo cluster decay
  9. ^ The nuclide with the lowest atomic number known to undergo spontaneous fission as the main decay mode

Actinides vs fission productsEdit

Actinides and fission products by half-life
Actinides[1] by decay chain Half-life
range (y)
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 155Euþ
244Cmƒ 241Puƒ 250Cf 227Ac 10–29 90Sr 85Kr 113mCdþ
232Uƒ 238Puƒ 243Cmƒ 29–97 137Cs 151Smþ 121mSn
248Bk[3] 249Cfƒ 242mAmƒ 141–351

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

241Amƒ 251Cfƒ[4] 430–900
226Ra 247Bk 1.3 k – 1.6 k
240Pu 229Th 246Cmƒ 243Amƒ 4.7 k – 7.4 k
245Cmƒ 250Cm 8.3 k – 8.5 k
239Puƒ 24.1 k
230Th 231Pa 32 k – 76 k
236Npƒ 233Uƒ 234U 150 k – 250 k 99Tc 126Sn
248Cm 242Pu 327 k – 375 k 79Se
1.53 M 93Zr
237Npƒ 2.1 M – 6.5 M 135Cs 107Pd
236U 247Cmƒ 15 M – 24 M 129I
244Pu 80 M

... nor beyond 15.7 M years[5]

232Th 238U 235Uƒ№ 0.7 G – 14.1 G

Legend for superscript symbols
₡  has thermal neutron capture cross section in the range of 8–50 barns
ƒ  fissile
metastable isomer
№  primarily a naturally occurring radioactive material (NORM)
þ  neutron poison (thermal neutron capture cross section greater than 3k barns)
†  range 4–97 y: Medium-lived fission product
‡  over 200,000 y: Long-lived fission product

ReferencesEdit

  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 U-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 y. No growth of Cf248 was detected, and a lower limit for the β half-life can be set at about 104 y. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 y."
  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 nearly eight quadrillion years.