Isotopes of einsteinium

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Einsteinium (Es) is an artificial element, and thus a standard atomic mass 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 19 known radioisotopes from 240Es to 258Es, and 3 nuclear isomers (250mEs, 254mEs, and 256mEs) The longest-lived isotope is 252Es with a half-life of 471.7 days.

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[1][n 1]
daughter
isotope(s)
nuclear
spin
excitation energy
240Es 99 141 240.06892(43)# 1# s 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 2] 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
258Es 99 159 258.09952(32)# 3# min
  1. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
    SF: Spontaneous fission
  2. ^ Most common isotope

Notes[edit]

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References[edit]

  1. ^ http://www.nucleonica.net/unc.aspx


Isotopes of californium Isotopes of einsteinium Isotopes of fermium
Table of nuclides