Isotopes of lanthanum (₅₇La)

Main isotopes^[1]			Decay
	abundance	half-life (t_1/2)	mode	product
¹³⁷La	synth	6×10⁴ y	ε	¹³⁷Ba
¹³⁸La	0.089%	1.05×10¹¹ y	ε	¹³⁸Ba
¹³⁸La	0.089%	1.05×10¹¹ y	β⁻	¹³⁸Ce
¹³⁹La	99.911%	stable

Standard atomic weight A_r°(La)

138.90547±0.00007^[2]
138.91±0.01 (abridged)^[3]

Naturally occurring lanthanum (₅₇La) is composed of one stable (¹³⁹La) and one radioactive (¹³⁸La) isotope, with the stable isotope, ¹³⁹La, being the most abundant (99.91% natural abundance). There are 39 radioisotopes that have been characterized, with the most stable being ¹³⁸La, with a half-life of 1.02×10¹¹ years; ¹³⁷La, with a half-life of 60,000 years and ¹⁴⁰La, with a half-life of 1.6781 days. The remaining radioactive isotopes have half-lives that are less than a day and the majority of these have half-lives that are less than 1 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.

The isotopes of lanthanum range in atomic weight from 115.96 u (¹¹⁶La) to 154.96 u (¹⁵⁵La).

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)		Note
Nuclide ^{[n 1]}	Excitation energy^{[n 5]}			Half-life ^{[n 4]}^{[n 5]}	Decay mode ^{[n 6]}	Daughter isotope ^{[n 7]}^{[n 8]}	Spin and parity ^{[n 9]}^{[n 5]}	Normal proportion	Range of variation	Note
¹¹⁶La^[4]	57	59		50(22) ms	p (~60%)	¹¹⁵Ba
¹¹⁶La^[4]	57	59		50(22) ms	β⁺ (~40%)	¹¹⁶Ba
¹¹⁷La	57	60	116.95007(43)#	23.5(26) ms	β⁺	¹¹⁷Ba	(3/2+, 3/2−)
¹¹⁷La	57	60	116.95007(43)#	23.5(26) ms	p	¹¹⁶Ba	(3/2+, 3/2−)
^117mLa	151(12) keV			10(5) ms			(9/2+)
¹¹⁸La	57	61	117.94673(32)#	200# ms	β⁺	¹¹⁸Ba
¹¹⁹La	57	62	118.94099(43)#	1# s	β⁺	¹¹⁹Ba	11/2−#
¹²⁰La	57	63	119.93807(54)#	2.8(2) s	β⁺	¹²⁰Ba
¹²⁰La	57	63	119.93807(54)#	2.8(2) s	β⁺, p	¹¹⁹Cs
¹²¹La	57	64	120.93301(54)#	5.3(2) s	β⁺	¹²¹Ba	11/2−#
¹²¹La	57	64	120.93301(54)#	5.3(2) s	β⁺, p	¹²⁰Cs	11/2−#
¹²²La	57	65	121.93071(32)#	8.6(5) s	β⁺	¹²²Ba
¹²²La	57	65	121.93071(32)#	8.6(5) s	β⁺, p	¹²¹Cs
¹²³La	57	66	122.92624(21)#	17(3) s	β⁺	¹²³Ba	11/2−#
¹²⁴La	57	67	123.92457(6)	29.21(17) s	β⁺	¹²⁴Ba	(7−, 8−)
^124mLa	100(100)# keV			21(4) s			low(+#)
¹²⁵La	57	68	124.920816(28)	64.8(12) s	β⁺	¹²⁵Ba	(11/2−)
^125mLa	107.0(10) keV			390(40) ms			(3/2+)
¹²⁶La	57	69	125.91951(10)	54(2) s	β⁺	¹²⁶Ba	(5)(+#)
^126mLa	210(410) keV			20(20) s			(0−, 1−, 2−)
¹²⁷La	57	70	126.916375(28)	5.1(1) min	β⁺	¹²⁷Ba	(11/2−)
^127mLa	14.8(12) keV			3.7(4) min	β⁺	¹²⁷Ba	(3/2+)
^127mLa	14.8(12) keV			3.7(4) min	IT	¹²⁷La	(3/2+)
¹²⁸La	57	71	127.91559(6)	5.18(14) min	β⁺	¹²⁸Ba	(5+)
^128mLa	100(100)# keV			<1.4 min	IT	¹²⁸La	(1+, 2−)
¹²⁹La	57	72	128.912693(22)	11.6(2) min	β⁺	¹²⁹Ba	3/2+
^129mLa	172.1(4) keV			560(50) ms	IT	¹²⁹La	11/2−
¹³⁰La	57	73	129.912369(28)	8.7(1) min	β⁺	¹³⁰Ba	3(+)
¹³¹La	57	74	130.91007(3)	59(2) min	β⁺	¹³¹Ba	3/2+
^131mLa	304.52(24) keV			170(10) μs			11/2−
¹³²La	57	75	131.91010(4)	4.8(2) h	β⁺	¹³²Ba	2−
^132mLa	188.18(11) keV			24.3(5) min	IT (76%)	¹³²La	6−
^132mLa	188.18(11) keV			24.3(5) min	β⁺ (24%)	¹³²Ba	6−
¹³³La	57	76	132.90822(3)	3.912(8) h	β⁺	¹³³Ba	5/2+
¹³⁴La	57	77	133.908514(21)	6.45(16) min	β⁺	¹³⁴Ba	1+
¹³⁵La	57	78	134.906977(11)	19.5(2) h	β⁺	¹³⁵Ba	5/2+
¹³⁶La	57	79	135.90764(6)	9.87(3) min	β⁺	¹³⁶Ba	1+
^136mLa	255(9) keV			114(3) ms	IT	¹³⁶La	(8)(−#)
¹³⁷La	57	80	136.906494(14)	6(2)×10⁴ y	EC	¹³⁷Ba	7/2+			extinct
¹³⁸La^{[n 10]}	57	81	137.907112(4)	1.02(1)×10¹¹ y	β⁺ (66.4%)	¹³⁸Ba	5+	9.0(1)×10⁻⁴
¹³⁸La^{[n 10]}	57	81	137.907112(4)	1.02(1)×10¹¹ y	β⁻ (33.6%)	¹³⁸Ce	5+	9.0(1)×10⁻⁴
^138mLa	72.57(3) keV			116(5) ns			(3)+
¹³⁹La^{[n 11]}	57	82	138.9063533(26)	Stable			7/2+	0.99910(1)
¹⁴⁰La^{[n 11]}	57	83	139.9094776(26)	1.6781(3) d	β⁻	¹⁴⁰Ce	3−
¹⁴¹La	57	84	140.910962(5)	3.92(3) h	β⁻	¹⁴¹Ce	(7/2+)
¹⁴²La	57	85	141.914079(6)	91.1(5) min	β⁻	¹⁴²Ce	2−
¹⁴³La	57	86	142.916063(17)	14.2(1) min	β⁻	¹⁴³Ce	(7/2)+
¹⁴⁴La	57	87	143.91960(5)	40.8(4) s	β⁻	¹⁴⁴Ce	(3−)
¹⁴⁵La	57	88	144.92165(10)	24.8(20) s	β⁻	¹⁴⁵Ce	(5/2+)
¹⁴⁶La	57	89	145.92579(8)	6.27(10) s	β⁻ (99.99%)	¹⁴⁶Ce	2−
¹⁴⁶La	57	89	145.92579(8)	6.27(10) s	β⁻, n (.007%)	¹⁴⁵Ce	2−
^146mLa	130(130) keV			10.0(1) s	β⁻	¹⁴⁶Ce	(6−)
¹⁴⁷La	57	90	146.92824(5)	4.015(8) s	β⁻ (99.96%)	¹⁴⁷Ce	(5/2+)
¹⁴⁷La	57	90	146.92824(5)	4.015(8) s	β⁻, n (.04%)	¹⁴⁶Ce	(5/2+)
¹⁴⁸La	57	91	147.93223(6)	1.26(8) s	β⁻ (99.85%)	¹⁴⁸Ce	(2−)
¹⁴⁸La	57	91	147.93223(6)	1.26(8) s	β⁻, n (.15%)	¹⁴⁷Ce	(2−)
¹⁴⁹La	57	92	148.93473(34)#	1.05(3) s	β⁻ (98.6%)	¹⁴⁹Ce	5/2+#
¹⁴⁹La	57	92	148.93473(34)#	1.05(3) s	β⁻, n (1.4%)	¹⁴⁸Ce	5/2+#
¹⁵⁰La	57	93	149.93877(43)#	510(30) ms	β⁻ (97.3%)	¹⁵⁰Ce	(3+)
¹⁵⁰La	57	93	149.93877(43)#	510(30) ms	β⁻, n (2.7%)	¹⁴⁹Ce	(3+)
¹⁵¹La	57	94	150.94172(43)#	300# ms [>300 ns]	β⁻	¹⁵¹Ce	5/2+#
¹⁵²La	57	95	151.94625(43)#	200# ms [>300 ns]	β⁻	¹⁵²Ce
¹⁵³La	57	96	152.94962(64)#	150# ms [>300 ns]	β⁻	¹⁵³Ce	5/2+#
¹⁵⁴La	57	97	153.95450(64)#	100# ms	β⁻	¹⁵⁴Ce
¹⁵⁵La	57	98	154.95835(86)#	60# ms	β⁻	¹⁵⁵Ce	5/2+#
This table header & footer: view

^ ^mLa – Excited nuclear isomer.
^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^ Bold half-life – nearly stable, half-life longer than age of universe.
^ ^a ^b ^c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Modes of decay:

EC: Electron capture

IT: Isomeric transition

n: Neutron emission

p: Proton emission
^ Bold italics symbol as daughter – Daughter product is nearly stable.
^ Bold symbol as daughter – Daughter product is stable.
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ Primordial radionuclide
^ ^a ^b Fission product

References

^ 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.
^ "Standard Atomic Weights: Lanthanum". CIAAW. 2005.
^ 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.
^ 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
₅₇La
₅₉" (PDF). Communications Physics. 5 (1): 1–8. doi:10.1038/s42005-022-01069-w. ISSN 2399-3650. S2CID 253512231.

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.

EC:	Electron capture
IT:	Isomeric transition
n:	Neutron emission
p:	Proton emission