Isotopes of berkelium
From Wikipedia, the free encyclopedia
Berkelium (97Bk) is an artificial 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 243Bk in 1949. There are twenty known radioisotopes, from 233Bk to 253Bk (except 237Bk), and seven nuclear isomers. The longest-lived isotope known is 247Bk with a half-life of 1,380 years; however 248Bk, which has not been observed to decay, may live longer.
The isotope commonly used in study, though, is 249Bk, as is it the only berkelium isotope that can be usefully extracted from reactor actinides and accumulated in weighable quantities.
List of isotopes
| Nuclide [n 1] |
Z | N | Isotopic mass (Da)[3] [n 2][n 3] |
Discovery year |
Half-life[1] |
Decay mode[1] [n 4] |
Daughter isotope |
Spin and parity[1] [n 5][n 6] | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy[n 6] | |||||||||||||||||||
| 233Bk | 97 | 136 | 233.05665(25)# | 2015 | 40(30) s | α (82%) | 229Am | 3/2−# | |||||||||||
| β+? (18%) | 233Cm | ||||||||||||||||||
| 234Bk | 97 | 137 | 234.05732(16)# | 2016 | 20(5) s | α (>80%) | 230Am | 3−# | |||||||||||
| β+ (<20%) | 234Cm | ||||||||||||||||||
| 235Bk[4] | 97 | 138 | 235.05665(43)# | 2026 | 1# min | α | 231Am | 3/2−# | |||||||||||
| β+ | 235Cm | ||||||||||||||||||
| 236Bk | 97 | 139 | 236.05748(39)# | 2017 | 26(10) s | β+ (99.96%) | 236Cm | 4+# | |||||||||||
| β+, SF (0.04%) | (various) | ||||||||||||||||||
| 238Bk | 97 | 141 | 238.05820(28)# | 1994 | 2.40(8) min | β+ (99.95%) | 238Cm | 1# | |||||||||||
| β+, SF (0.048%) | (various) | ||||||||||||||||||
| 239Bk | 97 | 142 | 239.05824(22)# | (2010)[n 7] | 100# s | β+ | 239Cm | (7/2+) | |||||||||||
| 240Bk | 97 | 143 | 240.05976(16)# | 1980 | 4.8(8) min | β+? | 240Cm | 7−# | |||||||||||
| α? | 236Am | ||||||||||||||||||
| β+, SF (0.0013%) | (various) | ||||||||||||||||||
| 241Bk | 97 | 144 | 241.06010(18)# | 2003 | 4.6(4) min | β+ | 241Cm | (7/2+) | |||||||||||
| 242Bk | 97 | 145 | 242.06200(14)# | 1972 | 7.0(13) min | β+ | 242Cm | 3+# | |||||||||||
| β+, SF (<3×10−5%) | (various) | ||||||||||||||||||
| 242mBk | 2000(200)# keV | 1979 | 600(100) ns | SF | (various) | ||||||||||||||
| 243Bk | 97 | 146 | 243.063006(5) | 1950 | 4.6(2) h | β+ (99.85%) | 243Cm | 3/2− | |||||||||||
| α (0.15%) | 239Am | ||||||||||||||||||
| 244Bk | 97 | 147 | 244.065179(15) | 1972 | 5.02(3) h | β+ (99.994%)[n 8] | 244Cm | 4− | |||||||||||
| α (0.006%) | 240Am | ||||||||||||||||||
| 244mBk | 1500(500)# keV | 2014 | 820(60) ns | SF | (various) | ||||||||||||||
| 245Bk | 97 | 148 | 245.0663598(19) | 1951 | 4.95(3) d | EC (99.88%) | 245Cm | 3/2− | |||||||||||
| α (0.12%) | 241Am | ||||||||||||||||||
| 246Bk | 97 | 149 | 246.06867(6) | 1954 | 1.80(2) d | β+ | 246Cm | 2(−) | |||||||||||
| 247Bk | 97 | 150 | 247.070306(6) | 1965 | 1.38(25)×103 y | α | 243Am | 3/2− | |||||||||||
| SF? | (various) | ||||||||||||||||||
| 248Bk | 97 | 151 | 248.07314(5) | 1956 | >9 y | α? | 244Am | 6+# | |||||||||||
| EC? | 248Cm | ||||||||||||||||||
| β−? | 248Cf | ||||||||||||||||||
| 248mBk[n 9] | −20(50) keV | 1965 | 23.7(2) h | β− (70%) | 248Cf | 1(−) | |||||||||||||
| EC (30%) | 248Cm | ||||||||||||||||||
| 249Bk[n 10] | 97 | 152 | 249.0749831(13) | 1954 | 327.2(3) d | β− | 249Cf | 7/2+ | |||||||||||
| α (0.00145%) | 245Am | ||||||||||||||||||
| SF (4.7×10−8%) | (various) | ||||||||||||||||||
| 249mBk | 8.777(14) keV | (1960)[n 11] | 300 μs | IT | 249Bk | 3/2− | |||||||||||||
| 250Bk | 97 | 153 | 250.078317(3) | 1954 | 3.212(5) h | β− | 250Cf | 2− | |||||||||||
| 250m1Bk | 35.59(10) keV | 1966 | 29(1) μs | IT | 250Bk | 4+ | |||||||||||||
| 250m2Bk | 85.6(16) keV | 1966 | 213(8) μs | IT | 250Bk | 7+ | |||||||||||||
| 251Bk | 97 | 154 | 251.080761(12) | 1967 | 55.6(11) min | β− | 251Cf | (3/2−) | |||||||||||
| 251mBk | 35.5(13) keV | (1966)[n 12] | 58(4) μs | IT | 251Bk | (7/2+) | |||||||||||||
| 252Bk | 97 | 155 | 252.08431(22)# | (1992) | 1.8(5) min | β− | 252Cf | ||||||||||||
| 253Bk | 97 | 156 | 253.08688(39)# | (1992) | 60# min | β−? | 253Cf | 3/2-# | |||||||||||
| This table header & footer: | |||||||||||||||||||
- mBk – Excited nuclear isomer.
- ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- Modes of decay:
EC: Electron capture SF: Spontaneous fission - ( ) spin value – Indicates spin with weak assignment arguments.
- # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- Populated, but not properties measured, not included in discovery database
- NUBASE2020 question-marks this decay, but it has been observed directly, see e.g. the IAEA Chart of Nuclides.
- Order of ground state and isomer is uncertain.
- Most common isotope
- Only published in a conference proceeding and not a refereed journal
- Half-life not measured, not included in discovery database
Actinides vs fission products
| Actinides[5] by decay chain | Half-life range (a) |
Fission products of 235U by yield[6] | ||||||
|---|---|---|---|---|---|---|---|---|
| 4n (Thorium) |
4n + 1 (Neptunium) |
4n + 2 (Radium) |
4n + 3 (Actinium) |
4.5–7% | 0.04–1.25% | <0.001% | ||
| 228Ra№ | 4–6 a | 155Euþ | ||||||
| 248Bk[7] | > 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 | |||||
| 241Amƒ | 251Cfƒ[8] | 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[9] | ||||||
| 232Th№ | 238U№ | 235Uƒ№ | 0.7–14.1 Ga | |||||
| ||||||||