Isotopes of erbium

Naturally occurring erbium (₆₈Er) is composed of 6 stable isotopes, with ¹⁶⁶Er being the most abundant (33.503% natural abundance). Thirty radioisotopes have been characterized with between 74 and 108 neutrons, or 142 to 177 nucleons, with the most stable being ¹⁶⁹Er with a half-life of 9.4 days, ¹⁷²Er with a half-life of 49.3 hours, ¹⁶⁰Er with a half-life of 28.58 hours, ¹⁶⁵Er with a half-life of 10.36 hours, and ¹⁷¹Er with a half-life of 7.516 hours. All of the remaining radioactive isotopes have half-lives that are less than 3.5 hours, and the majority of these have half-lives that are less than 4 minutes. This element also has 13 meta states, with the most stable being ^167mEr (t_1/2 2.269 seconds).

Main isotopes of erbium (₆₈Er)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^160Er syn 28.58 h ε ^160Ho ^162Er 0.139% stable ^164Er 1.601% stable ^165Er syn 10.36 h ε ^165Ho ^166Er 33.503% stable ^167Er 22.869% stable ^168Er 26.978% stable ^169Er syn 9.4 d β^− ^169Tm ^170Er 14.910% stable ^171Er syn 7.516 h β^− ^171Tm ^172Er syn 49.3 h β^− ^172Tm
Standard atomic weight Ar, standard(Er)	167.259(3)[1]

The isotopes of erbium range in atomic weight from 141.9723 u (¹⁴²Er) to 176.9541 u (¹⁷⁷Er). The primary decay mode before the most abundant stable isotope, ¹⁶⁶Er, is electron capture, and the primary mode after is beta decay. The primary decay products before ¹⁶⁶Er are holmium isotopes, and the primary products after are thulium isotopes.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope [n 6]	Spin and parity [n 7][n 4]	Natural abundance (mole fraction)
	Excitation energy[n 4]							Normal proportion	Range of variation
^142Er	68	74	141.97231(47)#				0+
^143Er	68	75	142.96634(64)#	200# ms			9/2−#
^144Er	68	76	143.96038(43)#	400# ms [>200 ns]	β^+	^144Ho	0+
^145Er	68	77	144.95739(43)#	900(300) ms	β^+	^145Ho	1/2+#
					β^+, p (rare)	^144Dy
^146Er	68	78	145.95200(32)#	1.7(6) s	β^+	^146Ho	0+
					β^+, p	^145Dy
^147Er	68	79	146.94949(32)#	~2.5 s	β^+	^147Ho	(1/2+)
					β^+, p	^146Dy
^147mEr	100(50)# keV			2.5(2) s	β^+	^147Ho	(11/2−)
^148Er	68	80	147.94455(21)#	4.6(2) s	β^+ (99.85%)	^148Ho	0+
					β^+, p (.15%)	^147Dy
^149Er	68	81	148.94231(3)	4(2) s	β^+ (93%)	^149Ho	(1/2+)
					β^+, p (7%)	^148Dy
^149m1Er	741.8(2) keV			8.9(2) s	β^+ (96.5%)	^149Ho	(11/2−)
					IT (3.5%)	^149Er
					β^+, p (.18%)	^148Dy
^149m2Er	2611.1(3) keV			0.61(8) μs			(19/2+)
^149m3Er	3242.7+X keV			4.8(1) μs			(27/2−)
^150Er	68	82	149.937914(18)	18.5(7) s	β^+	^150Ho	0+
^151Er	68	83	150.937449(18)	23.5(13) s	β^+	^151Ho	(7/2−)
^151m1Er	2585.5(6) keV			580(20) ms	IT (95.3%)	^151Er	(27/2−)
					β^+ (4.7%)	^151Ho
^151m2Er	10286+X keV			0.42(5) μs			(67/2, 69/2, 71/2)
^152Er	68	84	151.935050(11)	10.3(1) s	α (90%)	^148Dy	0+
					β^+ (10%)	^152Ho
^153Er	68	85	152.935063(9)	37.1(2) s	α (53%)	^149Dy	7/2(−)
					β^+ (47%)	^153Ho
^154Er	68	86	153.932783(6)	3.73(9) min	β^+ (99.53%)	^154Ho	0+
					α (.47%)	^150Dy
^155Er	68	87	154.933209(7)	5.3(3) min	β^+ (99.98%)	^155Ho	7/2−
					α (.022%)	^151Dy
^156Er	68	88	155.931065(26)	19.5(10) min	β^+	^156Ho	0+
^157Er	68	89	156.93192(3)	18.65(10) min	β^+	^157Ho	3/2−
^157mEr	155.4(3) keV			76(6) ms	IT	^157Er	(9/2+)
^158Er	68	90	157.929893(27)	2.29(6) h	EC	^158Ho	0+
^159Er	68	91	158.930684(5)	36(1) min	β^+	^159Ho	3/2−
^159m1Er	182.602(24) keV			337(14) ns			9/2+
^159m2Er	429.05(3) keV			590(60) ns			11/2−
^160Er	68	92	159.929083(26)	28.58(9) h	EC	^160Ho	0+
^161Er	68	93	160.929995(10)	3.21(3) h	β^+	^161Ho	3/2−
^161mEr	396.44(4) keV			7.5(7) μs			11/2−
^162Er	68	94	161.928778(4)	Observationally Stable[n 8]			0+	0.00139(5)
^163Er	68	95	162.930033(6)	75.0(4) min	β^+	^163Ho	5/2−
^163mEr	445.5(6) keV			580(100) ns			(11/2−)
^164Er	68	96	163.929200(3)	Observationally Stable[n 9]			0+	0.01601(3)
^165Er	68	97	164.930726(3)	10.36(4) h	EC	^165Ho	5/2−
^166Er	68	98	165.9302931(27)	Observationally Stable[n 10]			0+	0.33503(36)
^167Er	68	99	166.9320482(27)	Observationally Stable[n 11]			7/2+	0.22869(9)
^167mEr	207.801(5) keV			2.269(6) s	IT	^167Er	1/2−
^168Er	68	100	167.9323702(27)	Observationally Stable[n 12]			0+	0.26978(18)
^169Er	68	101	168.9345904(27)	9.392(18) d	β^−	^169Tm	1/2−
^170Er	68	102	169.9354643(30)	Observationally Stable[n 13]			0+	0.14910(36)
^171Er	68	103	170.9380298(30)	7.516(2) h	β^−	^171Tm	5/2−
^171mEr	198.6(1) keV			210(10) ns			1/2−
^172Er	68	104	171.939356(5)	49.3(3) h	β^−	^172Tm	0+
^173Er	68	105	172.94240(21)#	1.434(17) min	β^−	^173Tm	(7/2−)
^174Er	68	106	173.94423(32)#	3.2(2) min	β^−	^174Tm	0+
^175Er	68	107	174.94777(43)#	1.2(3) min	β^−	^175Tm	(9/2+)
^176Er	68	108	175.95008(43)#	20# s	β^−	^176Tm	0+
^177Er	68	109	176.95405(54)#	3# s	β^−	^177Tm	1/2−#

1. ^mEr – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition
   p:	Proton emission

6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.
8. Believed to undergo α decay to ¹⁵⁸Dy or β⁺β⁺ to ¹⁶²Dy with a half-life over 140×10¹² years
9. Believed to undergo α decay to ¹⁶⁰Dy or β⁺β⁺ to ¹⁶⁴Dy
10. Believed to undergo α decay to ¹⁶²Dy
11. Believed to undergo α decay to ¹⁶³Dy
12. Believed to undergo α decay to ¹⁶⁴Dy
13. Believed to undergo α decay to ¹⁶⁶Dy or β⁻β⁻ to ¹⁷⁰Yb with a half-life over 320×10¹⁵ years

Erbium-169

Radiopharmaceutical.

References

1. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.

• 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. Lay summary.
• 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.