Samarium-137

Properties and data of the isotope ¹³⁷Sm.

Content

General data

Name of the isotope:Samarium-137; Sm-137Symbol:¹³⁷Sm or 13762SmMass number A:137 (= number of nucleons)Atomic number Z:62 (= number of protons)Neutrons N:75Isotopic mass:136.92697(5) u (atomic weight of Samarium-137)Nuclide mass:136.8929607 u (calculated nuclear mass without electrons)Mass excess:-68.02701 MeVMass defect:1.208050684 u (per nucleus)Nuclear binding energy:1125.29196384 MeV (per nucleus)
8.21380996 MeV (average binding energy per nucleon)Separation energy:S_N = 9.29(4) MeV (first neutron)
S_P = 4.15(8) MeV (first proton)Half-life:45(1) sDecay constant λ:0.01540327067911 s^-1Specific activity α:6.820637186274 × 10⁺¹⁹ Bq g^-1
1843415455.7499 Ci g^-1Spin and parity:
(nuclear angular momentum)(9/2-)Year of discovery:1986

Radioactive Decay

Half-life T_½ = 45(1) s respectively 4.5 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹³⁷Pm	100 %	6.05(4) MeV

Parent Nuclides

Direct parent isotope is: ¹³⁷Eu.

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
^137mSm	180(50) keV	20 s	(1/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 75) and isobaric (same nucleon number A = 137) with Samarium-137. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 75	Isobar A = 137
42	¹¹⁷Mo
43	¹¹⁸Tc
44	¹¹⁹Ru
45	¹²⁰Rh
46	¹²¹Pd
47	¹²²Ag
48	¹²³Cd
49	¹²⁴In	¹³⁷In
50	¹²⁵Sn	¹³⁷Sn
51	¹²⁶Sb	¹³⁷Sb
52	¹²⁷Te	¹³⁷Te
53	¹²⁸I	¹³⁷I
54	¹²⁹Xe	¹³⁷Xe
55	¹³⁰Cs	¹³⁷Cs
56	¹³¹Ba	¹³⁷Ba
57	¹³²La	¹³⁷La
58	¹³³Ce	¹³⁷Ce
59	¹³⁴Pr	¹³⁷Pr
60	¹³⁵Nd	¹³⁷Nd
61	¹³⁶Pm	¹³⁷Pm
62	¹³⁷Sm	¹³⁷Sm
63	¹³⁸Eu	¹³⁷Eu
64	¹³⁹Gd	¹³⁷Gd
65	¹⁴⁰Tb	¹³⁷Tb
66	¹⁴¹Dy
67	¹⁴²Ho
68	¹⁴³Er
69	¹⁴⁴Tm