Samarium-131

Properties and data of the isotope ¹³¹Sm.

Content

General data

Name of the isotope:Samarium-131; Sm-131Symbol:¹³¹Sm or 13162SmMass number A:131 (= number of nucleons)Atomic number Z:62 (= number of protons)Neutrons N:69Isotopic mass:130.94618(43) u (atomic weight of Samarium-131)Nuclide mass:130.9121707 u (calculated nuclear mass without electrons)Mass excess:-50.13301 MeVMass defect:1.136851188 u (per nucleus)Nuclear binding energy:1058.97006051 MeV (per nucleus)
8.08374092 MeV (average binding energy per nucleon)Separation energy:S_N = 10.70(57) MeV (first neutron)
S_P = 2.03(45) MeV (first proton)Half-life:1.2(2) sDecay constant λ:0.57762265046662 s^-1Specific activity α:2.675788434615 × 10⁺²¹ Bq g^-1
72318606340.957 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2+~Year of discovery:1986

Radioactive Decay

Half-life T_½ = 1.2(2) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹³¹Pm	100 %	9.53(45) MeV
EE, p	¹³⁰Nd	?

Parent Nuclides

Direct parent isotope is: ¹³¹Eu.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 69) and isobaric (same nucleon number A = 131) with Samarium-131. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 69	Isobar A = 131
38	¹⁰⁷Sr
39	¹⁰⁸Y
40	¹⁰⁹Zr
41	¹¹⁰Nb
42	¹¹¹Mo
43	¹¹²Tc
44	¹¹³Ru
45	¹¹⁴Rh
46	¹¹⁵Pd
47	¹¹⁶Ag	¹³¹Ag
48	¹¹⁷Cd	¹³¹Cd
49	¹¹⁸In	¹³¹In
50	¹¹⁹Sn	¹³¹Sn
51	¹²⁰Sb	¹³¹Sb
52	¹²¹Te	¹³¹Te
53	¹²²I	¹³¹I
54	¹²³Xe	¹³¹Xe
55	¹²⁴Cs	¹³¹Cs
56	¹²⁵Ba	¹³¹Ba
57	¹²⁶La	¹³¹La
58	¹²⁷Ce	¹³¹Ce
59	¹²⁸Pr	¹³¹Pr
60	¹²⁹Nd	¹³¹Nd
61	¹³⁰Pm	¹³¹Pm
62	¹³¹Sm	¹³¹Sm
63	¹³²Eu	¹³¹Eu