ISOTOPES OF ERBIUM

Naturally occurring 'Erbium' ('Er') is composed of 6 stable isotopes, Er-162, Er-164, Er-166, Er-167, Er-168, and Er-170 with Er-166 being the most abundant (33.503% natural abundance). 29 radioisotopes have been characterized, with the most stable being Er-169 with a half life of 9.4 days, Er-172 with a half-life of 49.3 hours, Er-160 with a half-life of 28.58 hours, Er-165 with a half-life of 10.36 hours, and Er-171 with a half life of 7.516 hours. All of the remaining radioactive isotopes have half-lifes that are less than 3.5 hours, and the majority of these have half lifes that are less than 4 minutes. This element also has 13 meta states, with the most stable being Er-167m (t_½ 2.269 seconds).
The isotopes of erbium range in atomic weight from 142.9663 u (Er-143) to 176.9541 u (Er-177). The primary decay mode before the most abundant stable isotope, Er-166, is electron capture, and the primary mode after is beta decay. The primary decay products before Er-166 are element 67 (holmium) isotopes, and the primary products after are element 69 (thulium) isotopes.

Standard atomic mass: 167.259(3) u

Contents

Table

Notes

References

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
143Er	68	75	142.96634(64)#	200# ms	9/2-#
144Er	68	76	143.96038(43)#	400# ms [>200 ns]	0+
145Er	68	77	144.95739(43)#	900(300) ms	1/2+#
146Er	68	78	145.95200(32)#	1.7(6) s	0+
147Er	68	79	146.94949(32)#	~2.5 s	(1/2+)
147mEr	100(50)# keV			2.5(2) s	(11/2-)
148Er	68	80	147.94455(21)#	4.6(2) s	0+
149Er	68	81	148.94231(3)	4(2) s	(1/2+)
149m1Er	741.8(2) keV			8.9(2) s	(11/2-)
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	0+
151Er	68	83	150.937449(18)	23.5(13) s	(7/2-)
151m1Er	2585.5(6) keV			580(20) ms	(27/2-)
151m2Er	10286+X keV			0.42(5) µs	(67/2,69/2,71/2)
152Er	68	84	151.935050(11)	10.3(1) s	0+
153Er	68	85	152.935063(9)	37.1(2) s	7/2(-)
154Er	68	86	153.932783(6)	3.73(9) min	0+
155Er	68	87	154.933209(7)	5.3(3) min	7/2-
156Er	68	88	155.931065(26)	19.5(10) min	0+
157Er	68	89	156.93192(3)	18.65(10) min	3/2-
157mEr	155.4(3) keV			76(6) ms	(9/2+)
158Er	68	90	157.929893(27)	2.29(6) h	0+
159Er	68	91	158.930684(5)	36(1) min	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	0+
161Er	68	93	160.929995(10)	3.21(3) h	3/2-
161mEr	396.44(4) keV			7.5(7) µs	11/2-
162Er	68	94	161.928778(4)	STABLE [>140E+12 a]	0+	0.00139(5)
163Er	68	95	162.930033(6)	75.0(4) min	5/2-
163mEr	445.5(6) keV			580(100) ns	(11/2-)
164Er	68	96	163.929200(3)	STABLE	0+	0.01601(3)
165Er	68	97	164.930726(3)	10.36(4) h	5/2-
166Er	68	98	165.9302931(27)	STABLE	0+	0.33503(36)
167Er	68	99	166.9320482(27)	STABLE	7/2+	0.22869(9)
167mEr	207.801(5) keV			2.269(6) s	1/2-
168Er	68	100	167.9323702(27)	STABLE	0+	0.26978(18)
169Er	68	101	168.9345904(27)	9.392(18) d	1/2-
170Er	68	102	169.9354643(30)	STABLE [>320E+15 a]	0+	0.14910(36)
171Er	68	103	170.9380298(30)	7.516(2) h	5/2-
171mEr	198.6(1) keV			210(10) ns	1/2-
172Er	68	104	171.939356(5)	49.3(3) h	0+
173Er	68	105	172.94240(21)#	1.434(17) min	(7/2-)
174Er	68	106	173.94423(32)#	3.2(2) min	0+
175Er	68	107	174.94777(43)#	1.2(3) min	(9/2+)
176Er	68	108	175.95008(43)#	20# s	0+
177Er	68	109	176.95405(54)#	3# s	1/2-#

Notes

★ Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.

★ 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 Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in ''Nuclear Physics'' A729 (2003).

★ Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). ''Pure Appl. Chem.'' Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).

★ Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.

★
★ Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).

★
★ National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).

★
★ David R. Lide (ed.), Norman E. Holden in ''CRC Handbook of Chemistry and Physics, 85th Edition'', online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.