Isotopes of einsteinium

Isotopes of einsteinium (₉₉Es)

Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 252Es synth 471.7 d α 248Bk ε 252Cf β− 252Fm 253Es synth 20.47 d SF – 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 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, or around 1.293 years.

List of isotopes

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin
	excitation energy
240Es	99	141	240.06892(43)#	6(2) 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	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

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

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
• 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; 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.
  • 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. {{cite journal}}: Unknown parameter |laysummary= ignored (help)
• 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; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. {{cite web}}: Check date values in: |accessdate= (help)
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide (ed.). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9. {{cite book}}: Unknown parameter |nopp= ignored (|no-pp= suggested) (help)