Isotopes of einsteinium (₉₉Es)

Main isotopes^[1]			Decay
	abundance	half-life (t_1/2)	mode	product
²⁵²Es	synth	471.7 d	α	²⁴⁸Bk
			ε	²⁵²Cf
			β⁻	²⁵²Fm
²⁵³Es	synth	20.47 d	SF	–
²⁵³Es	synth	20.47 d	α	²⁴⁹Bk
²⁵⁴Es	synth	275.7 d	ε	²⁵⁴Cf
			β⁻	²⁵⁴Fm
			α	²⁵⁰Bk
²⁵⁵Es	synth	39.8 d	β⁻	²⁵⁵Fm
			α	²⁵¹Bk
			SF	–

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 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.

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]}
Nuclide ^{[n 1]}	Excitation energy^{[n 6]}			Half-life	Decay mode ^{[n 4]}	Daughter isotope	Spin and parity ^{[n 5]}^{[n 6]}
²⁴⁰Es^[2]	99	141	240.06892(43)#	6(2) s	α (70%)	²³⁶Bk
					β⁺ (25.2%)	²⁴⁰Cf
					β⁺, SF (4.8%)	(various)
²⁴¹Es^[3]	99	142	241.06854(24)#	4.3+2.4 −1.2 s	α	²³⁷Bk	3/2−#
²⁴¹Es^[3]	99	142	241.06854(24)#	4.3+2.4 −1.2 s	β⁺	²⁴¹Cf	3/2−#
²⁴²Es^[4]	99	143	242.06975(35)#	17.8(16) s	α (57%)	²³⁸Bk
					β⁺ (41.7%)	²⁴²Cf
					β⁺, SF (1.3%)	(various)
²⁴³Es^[4]	99	144	243.06955(25)#	23(3) s	β⁺ (61%)	²⁴³Cf	(7/2+,3/2−)
²⁴³Es^[4]	99	144	243.06955(25)#	23(3) s	α (39%)	²³⁹Bk	(7/2+,3/2−)
²⁴⁴Es	99	145	244.07088(20)#	37(4) s	β⁺ (94.69%)	²⁴⁴Cf
					α (5.3%)	²⁴⁰Bk
					β⁺, SF (0.011%)	(various)
²⁴⁵Es^[5]	99	146	245.07132(22)#	1.11(6) min	β⁺ (51%)	²⁴⁵Cf	(3/2−)
²⁴⁵Es^[5]	99	146	245.07132(22)#	1.11(6) min	α (49%)	²⁴¹Bk	(3/2−)
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+
²⁴⁹Es	99	150	249.07641(3)#	102.2(6) min	α (.57%)	²⁴⁵Bk	7/2+
²⁵⁰Es	99	151	250.07861(11)#	8.6(1) h	β⁺ (97%)	²⁵⁰Cf	(6+)
²⁵⁰Es	99	151	250.07861(11)#	8.6(1) h	α (3%)	²⁴⁶Bk	(6+)
^250mEs	200(150)# keV			2.22(5) h	EC (99%)	²⁵⁰Cf	1(−)
^250mEs	200(150)# keV			2.22(5) h	α (1%)	²⁴⁶Bk	1(−)
²⁵¹Es	99	152	251.079992(7)	33(1) h	EC (99.51%)	²⁵¹Cf	(3/2−)
²⁵¹Es	99	152	251.079992(7)	33(1) h	α (.49%)	²⁴⁷Bk	(3/2−)
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+
²⁵³Es^{[n 7]}	99	154	253.0848247(28)	20.47(3) d	SF (8.7×10⁻⁶%)	(various)	7/2+
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+)
^256mEs	0(100)# keV			7.6 h	β⁻, SF (.002%)	(various)	(8+)
²⁵⁷Es	99	158	257.09598(44)#	7.7(2) d	β⁻	²⁵⁷Fm	7/2+#
²⁵⁷Es	99	158	257.09598(44)#	7.7(2) d	α	²⁵³Bk	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).
^ Most common isotope

References

^ 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.
^ 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. hdl:1885/110868. ISSN 0370-2693.
^ 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.
^ ^a ^b Antalic, S.; Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Heinz, S.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Šáro, Š. (20 November 2009). "Studies of neutron-deficient mendelevium isotopes at SHIP". The European Physical Journal A. 43 (1): 35. Bibcode:2010EPJA...43...35A. doi:10.1140/epja/i2009-10896-0. ISSN 1434-601X. S2CID 121963345.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.

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.
"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
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.

EC:	Electron capture
IT:	Isomeric transition
SF:	Spontaneous fission