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 1.8×106 y α 146Sm
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
160Gd 21.9% stable
Standard atomic weight Ar°(Gd)
  • 157.25±0.03
  • 157.25±0.03 (abridged)[3][4]

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 have half-lives less than 24.6 seconds. Gadolinium isotopes have 10 metastable isomers, with the most stable being 143mGd (t1/2 = 110 seconds), 145mGd (t1/2 = 85 seconds) and 141mGd (t1/2 = 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.

Gadolinium-153 has a half-life of 240.4 ± 10 days 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.[6] It can also detect the loss of calcium in the hip and back bones, allowing the ability to diagnose osteoporosis.[7]

Gadolinium-148 would be ideal for radioisotope thermoelectric generators due to its 87-year half-life, high density, and dominant alpha decay mode. However, gadolinium-148 cannot be economically synthesized in sufficient quantities to power a RTG.[8]

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
134Gd 64 70 133.95537(43)# 0.4# s 0+
135Gd 64 71 134.95257(54)# 1.1(2) s 3/2−
136Gd 64 72 135.94734(43)# 1# s [>200 ns] β+ 136Eu
137Gd 64 73 136.94502(43)# 2.2(2) s β+ 137Eu 7/2+#
β+, p (rare) 136Sm
138Gd 64 74 137.94012(21)# 4.7(9) s β+ 138Eu 0+
138mGd 2232.7(11) keV 6(1) µs (8−)
139Gd 64 75 138.93824(21)# 5.7(3) s β+ 139Eu 9/2−#
β+, p (rare) 138Sm
139mGd 250(150)# keV 4.8(9) s 1/2+#
140Gd 64 76 139.93367(3) 15.8(4) s β+ 140Eu 0+
141Gd 64 77 140.932126(21) 14(4) s β+ (99.97%) 141Eu (1/2+)
β+, p (.03%) 140Sm
141mGd 377.8(2) keV 24.5(5) s β+ (89%) 141Eu (11/2−)
IT (11%) 141Gd
142Gd 64 78 141.92812(3) 70.2(6) s β+ 142Eu 0+
143Gd 64 79 142.92675(22) 39(2) s β+ 143Eu (1/2)+
β+, α (rare) 139Pm
β+, p (rare) 142Sm
143mGd 152.6(5) keV 110.0(14) s β+ 143Eu (11/2−)
β+, α (rare) 139Pm
β+, p (rare) 142Sm
144Gd 64 80 143.92296(3) 4.47(6) min β+ 144Eu 0+
145Gd 64 81 144.921709(20) 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 82 145.918311(5) 48.27(10) d EC 146Eu 0+
147Gd 64 83 146.919094(3) 38.06(12) h β+ 147Eu 7/2−
147mGd 8587.8(4) keV 510(20) ns (49/2+)
148Gd 64 84 147.918115(3) 86.9(39) y[9] α 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)×106 y α 146Sm 0+
151Gd 64 87 150.920348(4) 124(1) d EC 151Eu 7/2−
α (10−6%) 147Sm
152Gd[n 10] 64 88 151.9197910(27) 1.08(8)×1014 y α[n 11] 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 12] 0+ 0.0218(3)
155Gd[n 13] 64 91 154.9226220(27) Observationally Stable[n 14] 3/2− 0.1480(12)
155mGd 121.05(19) keV 31.97(27) ms IT 155Gd 11/2−
156Gd[n 13] 64 92 155.9221227(27) Stable[n 15] 0+ 0.2047(9)
156mGd 2137.60(5) keV 1.3(1) µs 7-
157Gd[n 13] 64 93 156.9239601(27) Stable[n 15] 3/2− 0.1565(2)
158Gd[n 13] 64 94 157.9241039(27) Stable[n 15] 0+ 0.2484(7)
159Gd[n 13] 64 95 158.9263887(27) 18.479(4) h β− 159Tb 3/2−
160Gd[n 13] 64 96 159.9270541(27) Observationally Stable[n 16] 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[10]		 β− 170Tb 0+
171Gd 64 107 392+145
−136 ms[10]		 β− 171Tb
172Gd 64 108 163+113
−99 ms[10]		 β− 172Tb 0+
This table header & footer:
  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. primordial radionuclide
  11. Theorized to also undergo β+β+ decay to 152Sm
  12. Believed to undergo α decay to 150Sm
  13. Fission product
  14. Believed to undergo α decay to 151Sm
  15. Theoretically capable of spontaneous fission
  16. Believed to undergo β−β− decay to 160Dy with a half-life over 1.3×1021 years

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. Elsevier BV. 194: 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; et al. (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. "PNNL: Isotope Sciences Program – Gadolinium-153". pnl.gov. Archived from the original on 2009-05-27.
  7. "Gadolinium". BCIT Chemistry Resource Center. British Columbia Institute of Technology. Archived from the original on 23 August 2011. Retrieved 30 March 2011.
  8. 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.
  9. Chiera, Nadine M.; Dressler, Rugard; Sprung, Peter; Talip, Zeynep; Schumann, Dorothea (2023). "Determination of the half-life of gadolinium-148". Applied Radiation and Isotopes. Elsevier BV. 194: 110708. doi:10.1016/j.apradiso.2023.110708. ISSN 0969-8043.
  10. 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.
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