Lanthanum-131m

Properties and data of the isotope ¹³¹La.

Content

General data

Name of the isotope:Lanthanum-131m; La-131mSymbol:¹³¹La or 13157LaMass number A:131 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:74Isotopic mass:130.91007(3) u (atomic weight of Lanthanum-131m)
Excitation energy: 304.52(24) keVNuclide mass:130.8788031 u (calculated nuclear mass without electrons)Mass excess:-83.76926 MeVMass defect:1.177160608 u (per nucleus)Nuclear binding energy:1096.51804339 MeV (per nucleus)
8.37036674 MeV (average binding energy per nucleon)Half-life:170(7) μsDecay constant λ:4077.336356235 s^-1Specific activity α:1.888791836199 × 10⁺²⁵ Bq g^-1
5.104842800538 × 10⁺¹⁴ Ci g^-1Spin and parity:
(nuclear angular momentum)11/2-

Radioactive Decay

Half-life T_½ = 170(7) μs respectively 1.70 × 10^-4 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹³¹La	100 %

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
¹³¹La		59(2) min	3/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 74) and isobaric (same nucleon number A = 131) with Lanthanum-131m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 74	Isobar A = 131
41	¹¹⁵Nb
42	¹¹⁶Mo
43	¹¹⁷Tc
44	¹¹⁸Ru
45	¹¹⁹Rh
46	¹²⁰Pd
47	¹²¹Ag	¹³¹Ag
48	¹²²Cd	¹³¹Cd
49	¹²³In	¹³¹In
50	¹²⁴Sn	¹³¹Sn
51	¹²⁵Sb	¹³¹Sb
52	¹²⁶Te	¹³¹Te
53	¹²⁷I	¹³¹I
54	¹²⁸Xe	¹³¹Xe
55	¹²⁹Cs	¹³¹Cs
56	¹³⁰Ba	¹³¹Ba
57	¹³¹La	¹³¹La
58	¹³²Ce	¹³¹Ce
59	¹³³Pr	¹³¹Pr
60	¹³⁴Nd	¹³¹Nd
61	¹³⁵Pm	¹³¹Pm
62	¹³⁶Sm	¹³¹Sm
63	¹³⁷Eu	¹³¹Eu
64	¹³⁸Gd
65	¹³⁹Tb
66	¹⁴⁰Dy
67	¹⁴¹Ho