Isotopes of gadolinium

Naturally occurring gadolinium (₆₄Gd) is composed of 6 stable isotopes, ¹⁵⁴Gd, ¹⁵⁵Gd, ¹⁵⁶Gd, ¹⁵⁷Gd, ¹⁵⁸Gd and ¹⁶⁰Gd, and 1 radioisotope, ¹⁵²Gd, with ¹⁵⁸Gd being the most abundant (24.84% natural abundance). The predicted double beta decay of ¹⁶⁰Gd has never been observed; only a lower limit on its half-life of more than 1.3×10²¹ years has been set experimentally.^[5]

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 1.79×10^6 y α ^146Sm ^152Gd 0.2% 1.08×10^14 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 ^160Gd 21.9% stable
Standard atomic weight Ar°(Gd)
	157.25±0.03^[3] 157.25±0.03 (abridged)^[4]
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Thirty-three radioisotopes have been characterized, with the most stable being alpha-decaying ¹⁵²Gd (naturally occurring) with a half-life of 1.08×10¹⁴ years, and ¹⁵⁰Gd with a half-life of 1.79×10⁶ years. All of the remaining radioactive isotopes have half-lives less than 100 years, the majority of these having half-lives less than 24.6 seconds. Gadolinium isotopes have 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 primary decay mode at atomic weights lower than the most abundant stable isotope, ¹⁵⁸Gd, is electron capture, and the primary mode at higher atomic weights is beta decay. The primary decay products for isotopes lighter than ¹⁵⁸Gd are isotopes of europium and the primary products of heavier isotopes are isotopes of terbium.

List of isotopes

Nuclide ^[n 1]	Z	N	Isotopic mass (Da) ^[n 2]^[n 3]	Half-life ^[n 4]^[n 5]	Decay mode ^[n 6]	Daughter isotope ^[n 7]^[n 8]	Spin and parity ^[n 9]^[n 5]	Natural abundance (mole fraction)
	Excitation energy^[n 5]							Normal proportion	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	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(10) 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 10]	^144Sm	0+
^149Gd	64	85	148.919341(4)	9.28(10) d	β^+	^149Eu	7/2−
					α (4.34×10^−4%)	^145Sm
^150Gd	64	86	149.918659(7)	1.79(8)×10^6 y	α^[n 11]	^146Sm	0+
^151Gd	64	87	150.920348(4)	124(1) d	EC	^151Eu	7/2−
					α (1.1(6)×10^−6%)	^147Sm
^152Gd^[n 12]	64	88	151.9197910(27)	1.08(8)×10^14 y	α^[n 13]	^148Sm	0+	0.0020(1)
^153Gd	64	89	152.9217495(27)	240.4(10) d	EC	^153Eu	3/2−
^153m1Gd	95.1737(12) keV			3.5(4) μs			(9/2+)
^153m2Gd	171.189(5) keV			76.0(14) μs			(11/2−)
^154Gd	64	90	153.9208656(27)	Observationally Stable^[n 14]			0+	0.0218(3)
^155Gd^[n 15]	64	91	154.9226220(27)	Observationally Stable^[n 16]			3/2−	0.1480(12)
^155mGd	121.05(19) keV			31.97(27) ms	IT	^155Gd	11/2−
^156Gd^[n 15]	64	92	155.9221227(27)	Stable			0+	0.2047(9)
^156mGd	2137.60(5) keV			1.3(1) μs			7-
^157Gd^[n 15]	64	93	156.9239601(27)	Stable			3/2−	0.1565(2)
^158Gd^[n 15]	64	94	157.9241039(27)	Stable			0+	0.2484(7)
^159Gd^[n 15]	64	95	158.9263887(27)	18.479(4) h	β^−	^159Tb	3/2−
^160Gd^[n 15]	64	96	159.9270541(27)	Observationally Stable^[n 17]			0+	0.2186(19)
^161Gd	64	97	160.9296692(29)	3.646(3) min	β^−	^161Tb	5/2−
^162Gd	64	98	161.930985(5)	8.4(2) min	β^−	^162Tb	0+
^163Gd	64	99	162.93399(32)#	68(3) s	β^−	^163Tb	7/2+#
^164Gd	64	100	163.93586(43)#	45(3) s	β^−	^164Tb	0+
^165Gd	64	101	164.93938(54)#	10.3(16) s	β^−	^165Tb	1/2−#
^166Gd	64	102	165.94160(64)#	4.8(10) s	β^−	^166Tb	0+
^167Gd	64	103	166.94557(64)#	4.2(3) s	β^−	^167Tb	5/2−#
^168Gd	64	104	167.94836(75)#	3.03(16) s	β^−	^168Tb	0+
^169Gd	64	105	168.95287(86)#	750(210) ms	β^−	^169Tb	7/2−#
^170Gd	64	106		675+94 −75 ms^[6]	β^−	^170Tb	0+
^171Gd	64	107		392+145 −136 ms^[6]	β^−	^171Tb
^172Gd	64	108		163+113 −99 ms^[6]	β^−	^172Tb	0+
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. Theorized to also undergo β⁺β⁺ decay to ¹⁴⁸Sm
11. Theorized to also undergo β⁺β⁺ decay to ¹⁵⁰Sm
12. primordial radionuclide
13. Theorized to also undergo β⁺β⁺ decay to ¹⁵²Sm
14. Believed to undergo α decay to ¹⁵⁰Sm
15. Fission product
16. Believed to undergo α decay to ¹⁵¹Sm
17. Believed to undergo β⁻β⁻ decay to ¹⁶⁰Dy with a half-life over 1.3×10²¹ 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]

References

1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
2. Chiera, Nadine M.; Dressler, Rugard; Sprung, Peter; Talip, Zeynep; Schumann, Dorothea (2023). "Determination of the half-life of gadolinium-148". Applied Radiation and Isotopes. 194. Elsevier BV: 110708. doi:10.1016/j.apradiso.2023.110708. ISSN 0969-8043.
3. "Standard Atomic Weights: Gadolinium". CIAAW. 1969.
4. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
5. F. A. Danevich; et al. (2001). "Quest for double beta decay of ¹⁶⁰Gd and Ce isotopes". Nuclear Physics A. 694 (1–2): 375–391. arXiv:nucl-ex/0011020. Bibcode:2001NuPhA.694..375D. doi:10.1016/S0375-9474(01)00983-6. S2CID 11874988.
6. Kiss, G. G.; Vitéz-Sveiczer, A.; Saito, Y.; et al. (2022). "Measuring the β-decay properties of neutron-rich exotic Pm, Sm, Eu, and Gd isotopes to constrain the nucleosynthesis yields in the rare-earth region". The Astrophysical Journal. 936 (107): 107. Bibcode:2022ApJ...936..107K. doi:10.3847/1538-4357/ac80fc. hdl:2117/375253.
7. Council, National Research; Sciences, Division on Engineering Physical; Board, Aeronautics Space Engineering; Board, Space Studies; Committee, Radioisotope Power Systems (2009). Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration. CiteSeerX 10.1.1.367.4042. doi:10.17226/12653. ISBN 978-0-309-13857-4.
8. . pnl.gov. Archived from the original on 2009-05-27.
9. . BCIT Chemistry Resource Center. British Columbia Institute of Technology. Archived from the original on 23 August 2011. Retrieved 30 March 2011.

• 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.
• "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
• 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.