Samarium-139m

Properties and data of the isotope ¹³⁹Sm.

Content

General data

Name of the isotope:Samarium-139m; Sm-139mSymbol:¹³⁹Sm or 13962SmMass number A:139 (= number of nucleons)Atomic number Z:62 (= number of protons)Neutrons N:77Isotopic mass:138.922297(12) u (atomic weight of Samarium-139m)
Excitation energy: 457.38(23) keVNuclide mass:138.8882877 u (calculated nuclear mass without electrons)Mass excess:-72.37988 MeVMass defect:1.230053516 u (per nucleus)Nuclear binding energy:1145.78746983 MeV (per nucleus)
8.24307532 MeV (average binding energy per nucleon)Half-life:10.7(6) sDecay constant λ:0.064780110332705 s^-1Specific activity α:2.826919922795 × 10⁺²⁰ Bq g^-1
7640324115.6638 Ci g^-1Spin and parity:
(nuclear angular momentum)11/2-Magnetic dipole moment:μ(μ_N) = 1.1(2)Nuclear g-factor:g_l = 0.2

Radioactive Decay

Half-life T_½ = 10.7(6) s respectively 1.07 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹³⁹Sm	97.7(5) %
EE/β⁺	¹³⁹Pm	6.3(5) %

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
¹³⁹Sm		2.57(10) min	1/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 77) and isobaric (same nucleon number A = 139) with Samarium-139m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 77	Isobar A = 139
43	¹²⁰Tc
44	¹²¹Ru
45	¹²²Rh
46	¹²³Pd
47	¹²⁴Ag
48	¹²⁵Cd
49	¹²⁶In
50	¹²⁷Sn	¹³⁹Sn
51	¹²⁸Sb	¹³⁹Sb
52	¹²⁹Te	¹³⁹Te
53	¹³⁰I	¹³⁹I
54	¹³¹Xe	¹³⁹Xe
55	¹³²Cs	¹³⁹Cs
56	¹³³Ba	¹³⁹Ba
57	¹³⁴La	¹³⁹La
58	¹³⁵Ce	¹³⁹Ce
59	¹³⁶Pr	¹³⁹Pr
60	¹³⁷Nd	¹³⁹Nd
61	¹³⁸Pm	¹³⁹Pm
62	¹³⁹Sm	¹³⁹Sm
63	¹⁴⁰Eu	¹³⁹Eu
64	¹⁴¹Gd	¹³⁹Gd
65	¹⁴²Tb	¹³⁹Tb
66	¹⁴³Dy	¹³⁹Dy
67	¹⁴⁴Ho
68	¹⁴⁵Er
69	¹⁴⁶Tm