Isotopes of einsteinium

(Redirected from Einsteinium-250m)

Einsteinium (99Es) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be discovered (in nuclear fallout from the Ivy Mike H-bomb test) was 253Es in 1952. There are 18 known radioisotopes from 240Es to 257Es, and 4 nuclear isomers. The longest-lived isotope is 252Es with a half-life of 471.7 days, or around 1.293 years.

Isotopes of einsteinium (99Es)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
252Es synth 471.7 d α 248Bk
ε 252Cf
β 252Fm
253Es synth 20.47 d SF
α 249Bk
254Es synth 275.7 d ε 254Cf
β 254Fm
α 250Bk
255Es synth 39.8 d β 255Fm
α 251Bk
SF

List of isotopes

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

Spin and
parity[1]
[n 5][n 6]
Excitation energy[n 6]
240Es 99 141 240.06895(39)# 6.0(17) s α (70%) 236Bk 4−#
β+ (30%) 240Cf
β+, SF (0.16%) (various)
241Es[3] 99 142 241.06859(25)# 4.3+2.4
−1.2
 s
α 237Bk 3/2−#
β+? 241Cf
242Es[4] 99 143 242.06957(28)# 16.9(8) s β+ 242Cf 2+#
α (41%) 238Bk
β+, SF (1.5%) (various)
243Es 99 144 243.06951(22)# 22.1(14) s α (61%) 239Bk (7/2+)
β+ (39%) 243Cf
244Es 99 145 244.07088(20)# 37(4) s β+ (95%) 244Cf 6+#
α (5%) 240Bk
β+, SF (0.011%) (various)
245Es 99 146 245.07119(18)# 1.11(6) min β+ (51%) 245Cf (3/2−)
α (49%) 241Bk
245mEs[n 7] 30(15)# keV >50# us IT? 245Es 7/2+#
α? 241Bk
β+? 245Cf
246Es 99 147 246.072806(97) 7.5(5) min β+ (90.1%) 246Cf 4−#
α (9.9%) 242Bk
β+, SF (.003%) (various)
247Es 99 148 247.073622(21) 4.55(26) min β+ (93%) 247Cf (7/2+)
α (7%) 243Bk
SF? (various)
248Es 99 149 248.075469(56)# 24(3) min β+ (99.75%) 248Cf 2−#
α (.25%) 244Bk
β+, SF (3.5×10−4%) (various)
249Es 99 150 249.076409(32)# 102.2(6) min β+ (99.43%) 249Cf 7/2+
α (.57%) 245Bk
250Es 99 151 250.07861(11)# 8.6(1) h β+ 250Cf 6(+)
α? 246Bk
250mEs[n 7] 200(150)# keV 2.22(5) h β+ 250Cf 1(−)
α? 246Bk
251Es 99 152 251.0799914(57) 33(1) h EC (99.5%) 251Cf 3/2−
α (.5%) 247Bk
252Es 99 153 252.082979(54) 471.7(19) d α (78(2)%) 248Bk (4+)
EC (22(2)%) 252Cf
253Es[n 8] 99 154 253.0848212(13) 20.47(3) d α 249Bk 7/2+
SF (8.7×10−6%) (various)
254Es 99 155 254.0880243(32) 275.7(5) d α[n 9] 250Bk 7+
β (1.74×10−4%) 254Fm
SF (<3×10−6%) (various)
254mEs 80.4(11) keV 39.3(2) h β (98(2)%) 254Fm 2+
IT (<3%) 254Es
α (0.32(1)%) 250Bk
EC (0.076(7)%) 254Cf
SF (<0.045%) (various)
255Es 99 156 255.090274(12) 39.8(12) d β (92.0%) 255Fm (7/2+)
α (8.0%) 251Bk
SF (.0041%) (various)
256Es 99 157 256.09360(11)# 7.6 h β 256Fm 7+#
β, SF (.002%) (various)
256mEs[n 7] 0(100)# keV 25.4(12) min β 256Fm 0+#
257Es 99 158 257.09598(44)# 7.7(2) d β 257Fm 7/2+#
α? 253Bk
This table header & footer:
  1. ^ mEs – 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. ^ Modes of decay:
    EC: Electron capture
    IT: Isomeric transition
    SF: Spontaneous fission
  5. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  6. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  7. ^ a b c Order of ground state and isomer is uncertain.
  8. ^ Most common isotope
  9. ^ Theoretically capable of electron capture to 254Cf[1]

References

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  1. ^ a b c d e 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. ^ 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.
  3. ^ Khuyagbaatar, J.; Albers, H. M.; Block, M.; Brand, H.; Cantemir, R. A.; Di Nitto, A.; Düllmann, Ch. E.; Götz, M.; Götz, S.; Heßberger, F. P.; Jäger, E.; Kindler, B.; Kratz, J. V.; Krier, J.; Kurz, N.; Lommel, B.; Lens, L.; Mistry, A.; Schausten, B.; Uusitalo, J.; Yakushev, A. (1 October 2020). "Search for Electron-Capture Delayed Fission in the New Isotope 244Md". Physical Review Letters. 125 (14): 142504. Bibcode:2020PhRvL.125n2504K. doi:10.1103/PhysRevLett.125.142504. PMID 33064498. S2CID 223546973.
  4. ^ Khuyagbaatar, J.; Cantemir, R. A.; Düllmann, Ch. E.; Jäger, E.; Kindler, B.; Krier, J.; Kurz, N.; Lommel, B.; Schausten, B.; Yakushev, A. (2024-03-18). "Decay properties of the neutron-deficient isotope Es 242". Physical Review C. 109 (3). doi:10.1103/PhysRevC.109.034311. ISSN 2469-9985.