Samarium-139

Properties and data of the isotope ¹³⁹Sm.

Content

General data

Name of the isotope:Samarium-139; Sm-139Symbol: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-139)Nuclide 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)Separation energy:S_N = 8.954(16) MeV (first neutron)
S_P = 4.73(3) MeV (first proton)Half-life:2.57(10) minDecay constant λ:0.004495117902464 s^-1Specific activity α:1.961611100772 × 10⁺¹⁹ Bq g^-1
530165162.37097 Ci g^-1Spin and parity:
(nuclear angular momentum)1/2+Magnetic dipole moment:μ(μ_N) = - 0.53(2)Nuclear g-factor:g_l = -1.06Charge radius:4.9556(34) femtometer fmYear of discovery:1971

Radioactive Decay

Half-life T_½ = 2.57(10) min (minutes) respectively 1.542 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹³⁹Pm	100 %	5.120(17) MeV

Parent Nuclides

Direct parent isotope is: ¹³⁹Eu.

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
^139mSm	457.38(23) keV	10.7(6) s	11/2-

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-139. 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