Isotopes of einsteinium

Isotopes of einsteinium (₉₉Es)
ε	252Cf
SF	–
β−	254Fm
α	251Bk
SF	–
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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 8 nuclear isomers. The longest-lived isotope is ²⁵²Es with a half-life of 471.7 days or 1.291 years; the second longest, ²⁵⁴Es with half-life of 275.7 days is more available.

List of isotopes

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]}
Nuclide ^{[n 1]}	Excitation energy^{[n 6]}			Half-life^[1]	Decay mode^[1] ^{[n 4]}	Daughter isotope	Spin and parity^[1] ^{[n 5]}^{[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	99	142	241.06859(25)#	4.3+2.4 −1.2 s^[3]	α	²³⁷Bk	3/2−#
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+)
²⁴³Es	99	144	243.06951(22)#	22.1(14) s	β⁺? (39%)	²⁴³Cf	(7/2+)
^243mEs^{[n 7]}	50(50)# keV			>50# μs	IT?	²⁴³Es	3/2−#
					α?	²³⁹Bk
					β⁺?	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−)
²⁴⁵Es	99	146	245.07119(18)#	1.11(6) min	α (49%)	²⁴¹Bk	(3/2−)
^245mEs^{[n 7]}	30(15)# keV			>50# μs	IT?	²⁴⁵Es	7/2+#
					α?	²⁴¹Bk
					β⁺?	²⁴⁵Cf
²⁴⁶Es	99	147	246.07281(10)	7.5(5) min	β⁺ (90.1%)	²⁴⁶Cf	4−#
					α (9.9%)	²⁴²Bk
					β⁺, SF (0.003%)	(various)
²⁴⁷Es	99	148	247.073622(21)	4.55(26) min	β⁺ (93%)	²⁴⁷Cf	(7/2+)
²⁴⁷Es	99	148	247.073622(21)	4.55(26) min	α (7%)	²⁴³Bk	(7/2+)
^247mEs^{[n 7]}	50(50)# keV			>20# μs	IT?	²⁴⁷Es	(3/2−)
					α?	²⁴³Bk
					β⁺	²⁴⁷Cf
²⁴⁸Es	99	149	248.07547(6)#	24(3) min	β⁺ (99.75%)	²⁴⁸Cf	2−#
					α (0.25%)	²⁴⁴Bk
					β⁺, SF (3.5×10⁻⁴%)	(various)
²⁴⁹Es	99	150	249.07641(3)#	102.2(6) min	β⁺ (99.43%)	²⁴⁹Cf	7/2+
²⁴⁹Es	99	150	249.07641(3)#	102.2(6) min	α (0.57%)	²⁴⁵Bk	7/2+
²⁵⁰Es	99	151	250.07861(11)#	8.6(1) h	β⁺	²⁵⁰Cf	6(+)
^250mEs^{[n 7]}	200(150)# keV			2.22(5) h	β⁺	²⁵⁰Cf	1(−)
²⁵¹Es	99	152	251.079991(6)	33(1) h	EC (99.5%)	²⁵¹Cf	3/2−
²⁵¹Es	99	152	251.079991(6)	33(1) h	α (0.5%)	²⁴⁷Bk	3/2−
^251mEs	8.4(10) keV			>200# μs	IT?	²⁵¹Es	(7/2+)
^251mEs	8.4(10) keV			>200# μs	EC?	²⁵¹Cf	(7/2+)
²⁵²Es	99	153	252.08298(5)	471.7(19) d	α (78%)	²⁴⁸Bk	(4+)
²⁵²Es	99	153	252.08298(5)	471.7(19) d	EC (22%)	²⁵²Cf	(4+)
²⁵³Es^{[n 8]}	99	154	253.0848212(13)	20.47(3) d	α	²⁴⁹Bk	7/2+
²⁵³Es^{[n 8]}	99	154	253.0848212(13)	20.47(3) d	SF (8.7×10⁻⁶%)	(various)	7/2+
^253mEs	106(4) keV			>10# μs	IT?	²⁵³Es	3/2−#
²⁵⁴Es	99	155	254.088024(3)	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%)	²⁵⁴Fm	2+
					IT (<3%)	²⁵⁴Es
					α (0.32%)	²⁵⁰Bk
					EC (0.076%)	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 (0.0041%)	(various)
²⁵⁶Es	99	157	256.09360(11)#	7.6 h	β⁻	²⁵⁶Fm	7+#
²⁵⁶Es	99	157	256.09360(11)#	7.6 h	β⁻, SF (0.002%)	(various)	7+#
^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+#
This table header & footer: view

^ ^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.
^ ^a ^b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ ^a ^b ^c ^d ^e Order of ground state and isomer is uncertain.
^ Most common isotope
^ Theoretically capable of electron capture to ²⁵⁴Cf

References

^ ^a ^b ^c ^d 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.
^ 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.
^ 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.
^ 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). arXiv:2408.01714. doi:10.1103/PhysRevC.109.034311. ISSN 2469-9985.

[2] Es – Excited nuclear isomer.

[4] ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

[TMS-5] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[6] Modes of decay:

EC: Electron capture

IT: Isomeric transition

SF: Spontaneous fission

[7] ( ) spin value – Indicates spin with weak assignment arguments.

[TNN-8] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[order-11] Order of ground state and isomer is uncertain.

[12] Most common isotope

[13] Theoretically capable of electron capture to ²⁵⁴Cf

[NUBASE2020-1] 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.

[AME2020_II-3] 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.

[9] 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.

[10] 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). arXiv:2408.01714. doi:10.1103/PhysRevC.109.034311. ISSN 2469-9985.

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