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Isotopes of lanthanum

Naturally occurring lanthanum (57La) is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.911% natural abundance). There are 39 radioisotopes that have been characterized, with the most stable being 138La, with a half-life of 1.03×1011 years; 137La, with a half-life of 60,000 years and 140La, with a half-life of 40.289 hours. The remaining radioactive isotopes have half-lives that are less than a day and the majority of these less than a minute. This element also has 12 nuclear isomers, the longest-lived of which is 132mLa, with a half-life of 24.3 minutes. Lighter isotopes mostly decay to isotopes of barium and heavy ones mostly decay to isotopes of cerium. 138La can decay to both.

Isotopes of lanthanum (57La)
Main isotopes[1] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
137La synth 6×104 y ε 137Ba
138La 0.0890% 1.03×1011 y β+ 138Ba
β− 138Ce
139La 99.9% stable
140La synth 40.289 h β− 140Ce
Standard atomic weight Ar°(La)
Stable Z/N chart of La and Ba

The known isotopes of lanthanum range from 116La to 155La.

List of isotopes

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Nuclide
[n 1]		 Z N Isotopic mass (Da)[4]
[n 2][n 3]		 Discovery
year[5][6]		 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
116La[7] 57 59 115.95701(35)# 2022 50(22) ms p (~60%) 115Ba
β+ (~40%) 116Ba
116mLa[7] 182 keV 2022 2.0+2.8
−0.8 μs		 IT 116La
117La 57 60 116.95033(22)# 2001 21.6(31) ms p (94%) 116Ba (3/2+)
β+ (6%) 117Ba
117mLa[7] 192 keV 2022 2.7+1.3
−0.7 μs		 IT 117La (7/2−)
118La[8] 57 61 117.94673(32)# 2025 200# ms [>310 ns] 1−#
119La[8] 57 62 118.94093(32)# 2025 1# s [>310 ns] 11/2−#
120La 57 63 119.93820(32)# 1984 2.8(2) s β+ 120Ba 4+[9]
β+, p (?%) 119Cs
121La 57 64 120.93324(32)# 1988 5.3(2) s β+ 121Ba 11/2−#
122La 57 65 121.93071(32)# 1984 8.6(5) s β+ 122Ba 2+[9]
β+, p (?%) 121Cs
123La 57 66 122.92630(21)# 1978 17(3) s β+ 123Ba 11/2−#
124La 57 67 123.924574(61) 1978 29.21(17) s β+ 124Ba (7−, 8−)
124mLa[n 10] 100(100)# keV 1997 21(4) s β+ 124Ba 2−#
125La 57 68 124.920816(28) 1973 64.8(12) s β+ 125Ba 11/2−#
125mLa 107.00(10) keV 1999 390(40) ms IT 125La (3/2+)
126La 57 69 125.919513(97) 1961 54(2) s β+ 126Ba 5−#
126mLa[n 10] 210(410) keV 1998 20(20) s β+ 126Ba 1−#
127La 57 70 126.916375(28) 1963 5.1(1) min β+ 127Ba (11/2−)
127mLa 14.2(4) keV 1973 3.7(4) min β+ 127Ba (3/2+)
128La 57 71 127.915592(58) 1961 5.18(14) min β+ 128Ba (5+)
128mLa[n 10] 100(100)# keV 1997 < 1.4 min β+ 128Ba (1+, 2−)
129La 57 72 128.912696(23) 1963 11.6(2) min β+ 129Ba (3/2+)
129mLa 172.33(20) keV 1969 560(50) ms IT 129La (11/2−)
130La 57 73 129.912369(28) 1961 8.7(1) min β+ 130Ba 3(+)
130mLa 214.0(5) keV 2012 742(28) ns IT 130La (5+)
131La 57 74 130.910070(30) 1951 59(2) min β+ 131Ba 3/2+
131mLa 304.52(24) keV 1966 170(10) μs IT 131La 11/2−
132La 57 75 131.910119(39) 1951 4.59(4) h β+ 132Ba 2−
132mLa 188.20(11) keV 1969 24.3(5) min IT (76%) 132La 6−
β+ (24%) 132Ba
133La 57 76 132.908218(30) 1950 3.912(8) h β+ 133Ba 5/2+
134La 57 77 133.908514(21) 1951 6.45(16) min β+ 134Ba 1+
134mLa 440(100)# keV 1985 29(4) μs IT 134La (6−)
135La 57 78 134.906984(10) 1948 18.91(2) h β+ 135Ba 5/2+
136La 57 79 135.907635(57) 1950 9.87(3) min β+ 136Ba 1+
136m1La 259.5(3) keV 1966 114(5) ms IT 136La (7−)
136m2La 2520.6(4) keV 2015 187(27) ns IT 136La (14+)
137La 57 80 136.9064504(18) 1948 6(2)×104 y EC 137Ba 7/2+
137mLa 1869.50(21) keV 1982 342(25) ns IT 137La 19/2−
138La[n 11] 57 81 137.90712404(45) 1947 1.03(1)×1011 y β+ (65.5%) 138Ba 5+ 8.881(71)×10−4
β− (34.5%) 138Ce
138m1La 72.57(3) keV 1975 116(5) ns IT 138La (3)+
138m2La 738.80(20) keV 2014 2.0(3) μs IT 138La 7−
139La[n 12] 57 82 138.90636293(65) 1924 Stable 7/2+ 0.9991119(71)
139mLa 1800.4(4) keV 2012 315(35) ns IT 139La (17/2+)
140La[n 12] 57 83 139.90948729(65) 1935 40.289(4) h β− 140Ce 3−
141La 57 84 140.9109712(44) 1951 3.92(3) h β− 141Ce (7/2+)
142La 57 85 141.9140908(67) 1953 91.1(5) min β− 142Ce 2−
142mLa 145.82(8) keV 1983 0.87(17) μs IT 142La (4)−
143La 57 86 142.9160795(79) 1951 14.2(1) min β− 143Ce (7/2)+
144La 57 87 143.919646(14) 1967 44.0(7) s β− 144Ce (3−)
145La 57 88 144.921808(13) 1974 24.8(20) s β− 145Ce (5/2+)
146La 57 89 145.9256880(18) 1974 9.9(1) s β− 146Ce (5−)
146mLa 141.5(24) keV 1979 6.08(22) s β− 146Ce (1−, 2−)
147La 57 90 146.928418(12) 1979 4.026(20) s β− (99.96%) 147Ce (5/2+)
β−, n (0.041%) 146Ce
148La 57 91 147.932679(21) 1982 1.414(25) s β− (99.82%) 148Ce (2−)
β−, n (0.18%) 147Ce
149La 57 92 148.93535(21) 1979 1.071(22) s β− (98.57%) 149Ce (3/2−)
β−, n (1.43%) 148Ce
150La 57 93 149.9395475(27) 1993 504(15) ms β− (97.3%) 150Ce (3+)
β−, n (2.7%) 149Ce
151La 57 94 150.94277(47) 1994 465(24) ms β− 151Ce 1/2+#
152La 57 95 151.94709(32)# 1994 287(16) ms β− 152Ce 2−#
153La 57 96 152.95055(32)# 1994 245(18) ms β− 153Ce 1/2+#
154La 57 97 153.95542(32)# 2017 161(15) ms β− 154Ce 2−#
155La 57 98 154.95928(43)# 2017 101(28) ms β− 155Ce 1/2+#
156La 57 99 155.96452(43)# 2017 84(78) ms β− 156Ce 4+#
157La 57 100 156.96879(32)# 2018 30# ms
[> 550 ns]		 1/2+#
158La[10] 57 101 2026
This table header & footer:
  1. ↑ mLa – 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. 1 2 3 # – 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
    n:Neutron emission
    p:Proton emission
  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. 1 2 3 Order of ground state and isomer is uncertain.
  11. ↑ Primordial radionuclide
  12. 1 2 Fission product

See also

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Daughter products other than lanthanum

References

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  1. 1 2 3 4 5 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. ↑ "Standard Atomic Weights: Lanthanum". CIAAW. 2005.
  3. ↑ 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.
  4. ↑ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3) 030003. doi:10.1088/1674-1137/abddaf.
  5. ↑ FRIB Nuclear Data Group. "Discovery of Nuclides Project, Isotope Database". doi:10.11578/frib/2279152.
  6. ↑ FRIB Nuclear Data Group. "Discovery of Nuclides Project, Isomer Database". doi:10.11578/frib/2572219.
  7. 1 2 3 Zhang, Wei; Cederwall, Bo; Aktas, Özge; Liu, Xiaoyu; Ertoprak, Aysegül; Nyberg, Ayse; Auranen, Kalle; Alayed, Betool; Badran, Hussam; Boston, Helen; Doncel, Maria; Forsberg, Ulrika; Grahn, Tuomas; Greenlees, Paul T.; Guo, Song; Heery, Jacob; Hilton, Joshua; Jenkins, David; Julin, Rauno; Juutinen, Sakari; Luoma, Minna; Neuvonen, Olavi; Ojala, Joonas; Page, Robert D.; Pakarinen, Janne; Partanen, Jari; Paul, Edward S.; Petrache, Costel; Rahkila, Panu; Ruotsalainen, Panu; Sandzelius, Mikael; Sarén, Jan; Szwec, Stuart; Tann, Holly; Uusitalo, Juha; Wadsworth, Robert (14 November 2022). "Observation of the proton emitter 116
    57    La
    59    "     (PDF). Communications Physics. 5 (1): 1–8. doi:10.1038/s42005-022-01069-w. ISSN 2399-3650. S2CID 253512231.
  8. 1 2 Suzuki, H; Fukuda, N; Takeda, H; Shimizu, Y; Yoshimoto, M; Togano, Y; Sato, H; Kitamura, N; Hanai, S; Momota, S; Kusaka, K; Yanagisawa, Y; Ohtake, M; Sumikama, T; Fukunishi, N; Michimasa, S (7 November 2025). "Discovery of Proton-Rich Radioactive Isotopes in the Z = 60 Region Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 238U Beam". Progress of Theoretical and Experimental Physics. 2025 (11). doi:10.1093/ptep/ptaf149.
  9. 1 2 Jodidar, P.M.; Petrache, C.M.; Lv, B.F.; Lawrie, E.A.; Astier, A.; Guo, S.; Zheng, K.K.; Auranen, K.; Briscoe, A.D.; Grahn, T.; Greenlees, P.T.; Illana, A.; Joukainen, H.; Julin, R.; Louko, J.; Luoma, M.; Jutila, H.; Ojala, J.; Pakarinen, J.; Plaza, A.M.; Rahkila, P.; Ruotsalainen, P.; Sarén, J.; Tolosa-Delgado, A.; Uusitalo, J.; Zimba, G.; Kuti, I.; Krakó, A.; Andreoiu, C.; Joss, D.T.; Page, R.D.; Cederlöf, E.A.; Ertoprak, A. (August 2024). "First observation of excited states in 120La and its impact on the shape evolution in the A ≈ 120 mass region" (PDF). Physics Letters B. 855 138806. doi:10.1016/j.physletb.2024.138806.
  10. ↑ Sumikama, Toshiyuki; Fukuda, Naoki; Kubo, Toshiyuki; Suzuki, Hiroshi; Takeda, Hiroyuki; Inabe, Naohito; Kameda, Daisuke; Ahn, Deuk Soon; Murai, Daichi; Yoshida, Koichi; Kusaka, Kensuke; Yanagisawa, Yoshiyuki; Ohtake, Masao; Shimizu, Yohei; Sato, Yuki; Sato, Hiromi; Otsu, Hideaki; Baba, Hidetada; Lorusso, Giuseppe; Söderström, Pär-Anders; Isobe, Tadaaki; Imai, Nobuaki; Mukai, Momo; Kimura, Sota; Miyatake, Hiroari; Iwasa, Naohito; Yagi, Ayumi; Yokoyama, Rin; Tarasov, Oleg Borisovich; Geissel, Hans (15 February 2026). "Expanding the Isotopic Frontier: Seven New Neutron-Rich Rare-Earth Isotopes Observed at RIKEN RI Beam Factory". Journal of the Physical Society of Japan. 95 (2). doi:10.7566/JPSJ.95.024202.
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