Isotopes of gadolinium

Naturally occurring gadolinium (₆₄Gd) is composed of 6 stable isotopes, ¹⁵⁴Gd, ¹⁵⁵Gd, ¹⁵⁶Gd, ¹⁵⁷Gd, ¹⁵⁸Gd and ¹⁶⁰Gd, and 1 long-lived radioisotope, ¹⁵²Gd, with ¹⁵⁸Gd being the most abundant (24.84% natural abundance). The predicted double beta decay of ¹⁶⁰Gd has never been observed.

Isotopes of gadolinium (₆₄Gd)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 148Gd synth 86.9 y[2] α 144Sm 150Gd synth 1.79×106 y α 146Sm 151Gd synth 123.9 d ε 151Eu α 147Sm 152Gd 0.2% 1.08×1014 y α 148Sm 153Gd synth 240.6 d ε 153Eu 154Gd 2.18% stable 155Gd 14.8% stable 156Gd 20.5% stable 157Gd 15.7% stable 158Gd 24.8% stable 159Gd synth 18.479 h β− 159Tb 160Gd 21.9% stable
Standard atomic weight Ar°(Gd)
	157.249±0.002[3] 157.25±0.01 (abridged)[4]
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Thirty-three radioisotopes have been characterized, with the three most stable being alpha emitters: ¹⁵²Gd (naturally occurring) with a half-life of 1.08×10¹⁴ years, ¹⁵⁰Gd with a half-life of 1.79×10⁶ years, and ¹⁴⁸Gd (theoretically not beta-stable) with a half-life of 86.9 years. All of the remaining radioactive isotopes have half-lives less than a year, the majority of these having half-lives less than two minutes. There are also 10 metastable isomers, with the most stable being ^143mGd (t_1/2 = 110 seconds), ^145mGd (t_1/2 = 85 seconds) and ^141mGd (t_1/2 = 24.5 seconds).

The isotopes with atomic masses lower than the most abundant stable isotope, ¹⁵⁸Gd, primarily decay by electron capture to isotopes of europium. At higher atomic masses, the primary decay mode is beta decay to isotopes of terbium.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da)[5] [n 2][n 3]	Half-life[1] [n 4][n 5]	Decay mode[1] [n 6]	Daughter isotope [n 7][n 8]	Spin and parity[1] [n 9][n 5]	Natural abundance (mole fraction)
	Excitation energy[n 5]							Normal proportion[1]	Range of variation
135Gd	64	71	134.95250(43)#	1.1(2) s	β+ (98%)	135Eu	(5/2+)
					β+, p (98%)	134Sm
136Gd	64	72	135.94730(32)#	1# s [>200 ns]	β+?	136Eu	0+
					β+, p?	135Sm
137Gd	64	73	136.94502(32)#	2.2(2) s	β+	137Eu	(7/2)+#
					β+, p?	136Sm
138Gd	64	74	137.94025(22)#	4.7(9) s	β+	138Eu	0+
138mGd	2232.6(11) keV			6.2(0.2) μs	IT	138Gd	(8−)
139Gd	64	75	138.93813(21)#	5.7(3) s	β+	139Eu	9/2−#
					β+, p?	138Sm
139mGd[n 10]	250(150)# keV			4.8(9) s	β+	139Eu	1/2+#
					β+, p?	138Sm
140Gd	64	76	139.933674(30)	15.8(4) s	β+ (67(8)%)	140Eu	0+
					EC (33(8)%)
141Gd	64	77	140.932126(21)	14(4) s	β+ (99.97%)	141Eu	(1/2+)
					β+, p (0.03%)	140Sm
141mGd	377.76(9) keV			24.5(5) s	β+ (89%)	141Eu	(11/2−)
					IT (11%)	141Gd
142Gd	64	78	141.928116(30)	70.2(6) s	EC (52(5)%)	142Eu	0+
					β+ (48(5)%)
143Gd	64	79	142.92675(22)	39(2) s	β+	143Eu	1/2+
					β+, p?	142Sm
					β+, α?	139Pm
143mGd	152.6(5) keV			110.0(14) s	β+	143Eu	11/2−
					β+, p?	142Sm
					β+, α?	139Pm
144Gd	64	80	143.922963(30)	4.47(6) min	β+	144Eu	0+
144mGd	3433.1(5) keV			145(30) ns	IT	144Gd	(10+)
145Gd	64	81	144.921710(21)	23.0(4) min	β+	145Eu	1/2+
145mGd	749.1(2) keV			85(3) s	IT (94.3%)	145Gd	11/2−
					β+ (5.7%)	145Eu
146Gd	64	82	145.9183185(44)	48.27(9) d	EC	146Eu	0+
147Gd	64	83	146.9191010(20)	38.06(12) h	β+	147Eu	7/2−
147mGd	8587.8(5) keV			510(20) ns	IT	147Gd	49/2+
148Gd	64	84	147.9181214(16)	86.9(39) y[2]	α[n 11]	144Sm	0+
149Gd	64	85	148.9193477(36)	9.28(10) d	β+	149Eu	7/2−
					α (4.3×10−4%)	145Sm
150Gd	64	86	149.9186639(65)	1.79(8)×106 y	α[n 12]	146Sm	0+
151Gd	64	87	150.9203549(32)	123.9(10) d	EC	151Eu	7/2−
					α (1.1×10−6%)	147Sm
152Gd[n 13]	64	88	151.9197984(11)	1.08(8)×1014 y	α[n 14]	148Sm	0+	0.0020(1)
153Gd	64	89	152.9217569(11)	240.6(7) d	EC	153Eu	3/2−
153m1Gd	95.1737(8) keV			3.5(4) μs	IT	153Gd	9/2+
153m2Gd	171.188(4) keV			76.0(14) μs	IT	153Gd	(11/2−)
154Gd[n 15]	64	90	153.9208730(11)	Observationally Stable[n 16]			0+	0.0218(2)
155Gd[n 15]	64	91	154.9226294(11)	Observationally Stable[n 17]			3/2−	0.1480(9)
155mGd	121.10(19) keV			31.97(27) ms	IT	155Gd	11/2−
156Gd[n 15]	64	92	155.9221301(11)	Stable			0+	0.2047(3)
156mGd	2137.60(5) keV			1.3(1) μs	IT	156Gd	7-
157Gd[n 15]	64	93	156.9239674(10)	Stable			3/2−	0.1565(4)
157m1Gd	63.916(5) keV			460(40) ns	IT	157Gd	5/2+
157m2Gd	426.539(23) keV			18.5(23) μs	IT	157Gd	11/2−
158Gd[n 15]	64	94	157.9241112(10)	Stable			0+	0.2484(8)
159Gd[n 15]	64	95	158.9263958(11)	18.479(4) h	β−	159Tb	3/2−
160Gd[n 15]	64	96	159.9270612(12)	Observationally Stable[n 18]			0+	0.2186(3)
161Gd	64	97	160.9296763(16)	3.646(3) min	β−	161Tb	5/2−
162Gd	64	98	161.9309918(43)	8.4(2) min	β−	162Tb	0+
163Gd	64	99	162.93409664(86)	68(3) s	β−	163Tb	7/2+
163mGd	138.22(20) keV			23.5(10) s	IT?	163Gd	1/2−
					β−	163Tb
164Gd	64	100	163.9359162(11)	45(3) s	β−	164Tb	0+
164mGd	1095.8(4) keV			589(18) ns	IT	164Gd	(4−)
165Gd	64	101	164.9393171(14)	11.6(10) s	β−	165Tb	1/2−#
166Gd	64	102	165.9416304(17)	5.1(8) s	β−	166Tb	0+
166mGd	1601.5(11) keV			950(60) ns	IT	166Gd	(6−)
167Gd	64	103	166.9454900(56)	4.2(3) s	β−	167Tb	5/2−#
168Gd	64	104	167.94831(32)#	3.03(16) s	β−	168Tb	0+
169Gd	64	105	168.95288(43)#	750(210) ms	β−	169Tb	7/2−#
					β−, n? (<0.7%)[6]	168Tb
170Gd	64	106	169.95615(54)#	675+94 −75 ms[6]	β−	170Tb	0+
					β−, n? (<3%)[6]	169Tb
171Gd	64	107	170.96113(54)#	392+145 −136 ms[6]	β−	171Tb	9/2+#
					β−, n? (<10%)[6]	170Tb
172Gd	64	108	171.96461(32)#	163+113 −99 ms[6]	β−	172Tb	0+#
					β−, n? (<50%)[6]	171Tb
This table header & footer: view

1. ^mGd – 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. Bold half-life – nearly stable, half-life longer than age of universe.
5. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
6. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition

7. Bold italics symbol as daughter – Daughter product is nearly stable.
8. Bold symbol as daughter – Daughter product is stable.
9. ( ) spin value – Indicates spin with weak assignment arguments.
10. Order of ground state and isomer is uncertain.
11. Theorized to also undergo β⁺β⁺ decay to ¹⁴⁸Sm
12. Theorized to also undergo β⁺β⁺ decay to ¹⁵⁰Sm
13. primordial radionuclide
14. Theorized to also undergo β⁺β⁺ decay to ¹⁵²Sm
15. Fission product
16. Believed to undergo α decay to ¹⁵⁰Sm
17. Believed to undergo α decay to ¹⁵¹Sm
18. Believed to undergo β⁻β⁻ decay to ¹⁶⁰Dy with a half-life over 3.1×10¹⁹ years

Gadolinium-148

With a half-life of 86.9±3.9 year via alpha decay alone,^[2] gadolinium-148 would be ideal for radioisotope thermoelectric generators. However, gadolinium-148 cannot be economically synthesized in sufficient quantities to power a RTG.^[7]

Gadolinium-153

Gadolinium-153 has a half-life of 240.4±10 d and emits gamma radiation with strong peaks at 41 keV and 102 keV. It is used as a gamma ray source for X-ray absorptiometry and fluorescence, for bone density gauges for osteoporosis screening, and for radiometric profiling in the Lixiscope portable x-ray imaging system, also known as the Lixi Profiler. In nuclear medicine, it serves to calibrate the equipment needed like single-photon emission computed tomography systems (SPECT) to make x-rays. It ensures that the machines work correctly to produce images of radioisotope distribution inside the patient. This isotope is produced in a nuclear reactor from europium or enriched gadolinium.^[8] It can also detect the loss of calcium in the hip and back bones, allowing the ability to diagnose osteoporosis.^[9]

See also

Daughter products other than gadolinium

• Isotopes of terbium
• Isotopes of europium
• Isotopes of samarium
• Isotopes of promethium