ISOTOPES OF SAMARIUM

Naturally occurring 'Samarium' ('Sm') is composed of 4 stable isotopes, ¹⁴⁴Sm, ¹⁵⁰Sm, ¹⁵²Sm and ¹⁵⁴Sm, and 3 extremely long-lived radioisotopes, ¹⁴⁷Sm (1.06y), ¹⁴⁸Sm (7y) and ¹⁴⁹Sm (>2y), with ¹⁵²Sm being the most abundant (26.75% natural abundance).
¹⁵¹Sm has a halflife of 90 years, and ¹⁴⁵Sm has a halflife of 340 days. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds. This element also has 5 meta states with the most stable being ^141mSm (t_½ 22.6 minutes), ^143m1Sm (t_½ 66 seconds) and ^139mSm (t_½ 10.7 seconds).
The primary decay mode before the most abundant stable isotope, ¹⁵²Sm, is electron capture, and the primary mode after is beta minus decay. The primary decay products before ¹⁵²Sm are element Pm (promethium) isotopes, and the primary products after are element Eu (europium) isotopes.

Standard atomic mass: 150.36(2) 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
128Sm	62	66	127.95808(54)#	0.5# s	0+
129Sm	62	67	128.95464(54)#	550(100) ms	5/2+#
130Sm	62	68	129.94892(43)#	1# s	0+
131Sm	62	69	130.94611(32)#	1.2(2) s	5/2+#
132Sm	62	70	131.94069(32)#	4.0(3) s	0+
133Sm	62	71	132.93867(21)#	2.90(17) s	(5/2+)
134Sm	62	72	133.93397(21)#	10(1) s	0+
135Sm	62	73	134.93252(17)	10.3(5) s	(7/2+)
135mSm	0(300)# keV			2.4(9) s	(3/2+,5/2+)
136Sm	62	74	135.928276(13)	47(2) s	0+
136mSm	2264.7(11) keV			15(1) µs	(8-)
137Sm	62	75	136.92697(5)	45(1) s	(9/2-)
137mSm	180(50)# keV			20# s	1/2+#
138Sm	62	76	137.923244(13)	3.1(2) min	0+
139Sm	62	77	138.922297(12)	2.57(10) min	1/2+
139mSm	457.40(22) keV			10.7(6) s	11/2-
140Sm	62	78	139.918995(13)	14.82(12) min	0+
141Sm	62	79	140.918476(9)	10.2(2) min	1/2+
141mSm	176.0(3) keV			22.6(2) min	11/2-
142Sm	62	80	141.915198(6)	72.49(5) min	0+
143Sm	62	81	142.914628(4)	8.75(8) min	3/2+
143m1Sm	753.99(16) keV			66(2) s	11/2-
143m2Sm	2793.8(13) keV			30(3) ms	23/2(-)
144Sm	62	82	143.911999(3)	STABLE	0+	0.0307(7)
144mSm	2323.60(8) keV			880(25) ns	6+
145Sm	62	83	144.913410(3)	340(3) d	7/2-
145mSm	8786.2(7) keV			990(170) ns [0.96(+19-15) µs]	(49/2+)
146Sm	62	84	145.913041(4)	1.03(5)E+8 a	0+
147Sm	62	85	146.9148979(26)	1.06(2)E+11 a	7/2-	0.1499(18)
148Sm	62	86	147.9148227(26)	7(3)E+15 a	0+	0.1124(10)
149Sm	62	87	148.9171847(26)	STABLE [>2E+15 a]	7/2-	0.1382(7)
150Sm	62	88	149.9172755(26)	STABLE	0+	0.0738(1)
151Sm	62	89	150.9199324(26)	90(8) a	5/2-
151mSm	261.13(4) keV			1.4(1) µs	(11/2)-
152Sm	62	90	151.9197324(27)	STABLE	0+	0.2675(16)
153Sm	62	91	152.9220974(27)	46.284(4) h	3/2+
153mSm	98.37(10) keV			10.6(3) ms	11/2-
154Sm	62	92	153.9222093(27)	STABLE [>2.3E+18 a]	0+	0.2275(29)
155Sm	62	93	154.9246402(28)	22.3(2) min	3/2-
156Sm	62	94	155.925528(10)	9.4(2) h	0+
156mSm	1397.55(9) keV			185(7) ns	5-
157Sm	62	95	156.92836(5)	8.03(7) min	(3/2-)
158Sm	62	96	157.92999(8)	5.30(3) min	0+
159Sm	62	97	158.93321(11)	11.37(15) s	5/2-
160Sm	62	98	159.93514(21)#	9.6(3) s	0+
161Sm	62	99	160.93883(32)#	4.8(8) s	7/2+#
162Sm	62	100	161.94122(54)#	2.4(5) s	0+
163Sm	62	101	162.94536(75)#	1# s	1/2-#
164Sm	62	102	163.94828(86)#	500# ms	0+
165Sm	62	103	164.95298(97)#	200# ms	5/2-#

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.