Open main menu

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.

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

List of isotopesEdit

Nuclide
[n 1]
Z N Isotopic mass (u)
[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
  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. ^ Most common isotope

ReferencesEdit

  1. ^ 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.