Isotopes of einsteinium
Einsteinium (99Es) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered (in nuclear fallout from an H-bomb test) was 253Es in 1952. There are 18 known radioisotopes from 240Es to 257Es, and 3 nuclear isomers (250mEs, 254mEs, and 256mEs). The longest-lived isotope is 252Es with a half-life of 471.7 days, or around 1.293 years.
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List of isotopes
| Nuclide [n 1] |
Z | N | Isotopic mass (Da) [n 2][n 3] |
Half-life |
Decay mode [n 4] |
Daughter isotope |
Spin and parity [n 5][n 6] |
|---|---|---|---|---|---|---|---|
| Excitation energy[n 6] | |||||||
| 240Es | 99 | 141 | 240.06892(43)# | 6(2) s[1] | α | 236Bk | |
| β+ (rare) | 240Cf | ||||||
| 241Es | 99 | 142 | 241.06854(24)# | 10(5) s [8(+6−5) s] |
α | 237Bk | (3/2−) |
| β+ (rare) | 241Cf | ||||||
| 242Es | 99 | 143 | 242.06975(35)# | 13.5(25) s | α (99.94%) | 238Bk | |
| β+, SF (.6%) | (various) | ||||||
| β+ (rare) | 242Cf | ||||||
| 243Es | 99 | 144 | 243.06955(25)# | 21(2) s | β+ (70%) | 243Cf | 3/2−# |
| α (30%) | 239Bk | ||||||
| 244Es | 99 | 145 | 244.07088(20)# | 37(4) s | β+ (94.69%) | 244Cf | |
| α (5.3%) | 240Bk | ||||||
| β+, SF (.01%) | (various) | ||||||
| 245Es | 99 | 146 | 245.07132(22)# | 1.1(1) min | β+ (60%) | 245Cf | (3/2−) |
| α (40%) | 241Bk | ||||||
| 246Es | 99 | 147 | 246.07290(24)# | 7.7(5) min | β+ (90.1%) | 246Cf | 4−# |
| α (9.9%) | 242Bk | ||||||
| β+, SF (.003%) | (various) | ||||||
| 247Es | 99 | 148 | 247.07366(3)# | 4.55(26) min | β+ (93%) | 247Cf | 7/2+# |
| α (7%) | 243Bk | ||||||
| SF (9×10−5%) | (various) | ||||||
| 248Es | 99 | 149 | 248.07547(6)# | 27(5) min | β+ (99.75%) | 248Cf | 2−#, 0+# |
| α (.25%) | 244Bk | ||||||
| β+, SF (3×10−5%) | (various) | ||||||
| 249Es | 99 | 150 | 249.07641(3)# | 102.2(6) min | β+ (99.43%) | 249Cf | 7/2+ |
| α (.57%) | 245Bk | ||||||
| 250Es | 99 | 151 | 250.07861(11)# | 8.6(1) h | β+ (97%) | 250Cf | (6+) |
| α (3%) | 246Bk | ||||||
| 250mEs | 200(150)# keV | 2.22(5) h | EC (99%) | 250Cf | 1(−) | ||
| α (1%) | 246Bk | ||||||
| 251Es | 99 | 152 | 251.079992(7) | 33(1) h | EC (99.51%) | 251Cf | (3/2−) |
| α (.49%) | 247Bk | ||||||
| 252Es | 99 | 153 | 252.08298(5) | 471.7(19) d | α (76%) | 248Bk | (5−) |
| EC (24%) | 252Cf | ||||||
| β− (.01%) | 252Fm | ||||||
| 253Es[n 7] | 99 | 154 | 253.0848247(28) | 20.47(3) d | α | 249Bk | 7/2+ |
| SF (8.7×10−6%) | (various) | ||||||
| 254Es | 99 | 155 | 254.088022(5) | 275.7(5) d | α | 250Bk | (7+) |
| EC (10−4%) | 254Cf | ||||||
| SF (3×10−6%) | (various) | ||||||
| β− (1.74×10−6%) | 254Fm | ||||||
| 254mEs | 84.2(25) keV | 39.3(2) h | β− (98%) | 254Fm | 2+ | ||
| IT (3%) | 254Es | ||||||
| α (.33%) | 250Bk | ||||||
| EC (.078%) | 254Cf | ||||||
| SF (.0045%) | (various) | ||||||
| 255Es | 99 | 156 | 255.090273(12) | 39.8(12) d | β− (92%) | 255Fm | (7/2+) |
| α (8%) | 251Bk | ||||||
| SF (.0041%) | (various) | ||||||
| 256Es | 99 | 157 | 256.09360(11)# | 25.4(24) min | β− | 256Fm | (1+, 0−) |
| 256mEs | 0(100)# keV | 7.6 h | β− (99.99%) | 256Fm | (8+) | ||
| β−, SF (.002%) | (various) | ||||||
| 257Es | 99 | 158 | 257.09598(44)# | 7.7(2) d | β− | 257Fm | 7/2+# |
| α | 253Bk | ||||||
- mEs – 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 IT: Isomeric transition 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).
- Most common isotope
References
- Konki, J.; et al. (10 Jan 2017). "Towards saturation of the electron-capture delayed fission probability: The new isotopes 240Es and 236Bk". Physics Letters B. 764: 265–270. Bibcode:2017PhLB..764..265K. doi:10.1016/j.physletb.2016.11.038. ISSN 0370-2693.
- Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- Isotopic compositions and standard atomic masses from:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
- Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.
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