Isotopes of einsteinium

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

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)^[1]^{[n 1]}	daughter isotope(s)	nuclear spin
nuclide symbol	excitation energy			half-life	decay mode(s)^[1]^{[n 1]}	daughter isotope(s)	nuclear spin
²⁴⁰Es	99	141	240.06892(43)#	1# s	α	²³⁶Bk
²⁴⁰Es	99	141	240.06892(43)#	1# s	β⁺ (rare)	²⁴⁰Cf
²⁴¹Es	99	142	241.06854(24)#	10(5) s [8(+6-5) s]	α	²³⁷Bk	(3/2-)
²⁴¹Es	99	142	241.06854(24)#	10(5) s [8(+6-5) s]	β⁺ (rare)	²⁴¹Cf	(3/2-)
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-#
²⁴³Es	99	144	243.06955(25)#	21(2) s	α (30%)	²³⁹Bk	3/2-#
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-)
²⁴⁵Es	99	146	245.07132(22)#	1.1(1) min	α (40%)	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 2]}	99	154	253.0848247(28)	20.47(3) d	α	²⁴⁹Bk	7/2+
²⁵³Es^{[n 2]}	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+#
²⁵⁸Es	99	159	258.09952(32)#	3# min

^ Abbreviations:
EC: Electron capture
IT: Isomeric transition
SF: Spontaneous fission
^ Most common isotope

Notes

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

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

Isotope masses from:
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter, J. K. Böhlke, P. De Bièvre, H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683. http://www.iupac.org/publications/pac/75/6/0683/pdf/.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. http://iupac.org/publications/pac/78/11/2051/pdf/. Lay summary.
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. Retrieved September 2005.
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0849304859.

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