Samarium-157

Properties and data of the isotope ¹⁵⁷Sm.

Content

General data

Name of the isotope:Samarium-157; Sm-157Symbol:¹⁵⁷Sm or 15762SmMass number A:157 (= number of nucleons)Atomic number Z:62 (= number of protons)Neutrons N:95Isotopic mass:156.928419(5) u (atomic weight of Samarium-157)Nuclide mass:156.8944097 u (calculated nuclear mass without electrons)Mass excess:-66.67727 MeVMass defect:1.379900004 u (per nucleus)Nuclear binding energy:1285.36857433 MeV (per nucleus)
8.18706098 MeV (average binding energy per nucleon)Separation energy:S_N = 5.388(10) MeV (first neutron)
S_P = 9.803(6) MeV (first proton)Half-life:8.03(7) minDecay constant λ:0.0014386616449978 s^-1Specific activity α:5.553732741003 × 10⁺¹⁸ Bq g^-1
150100884.89198 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2-)Year of discovery:1973

Radioactive Decay

Half-life T_½ = 8.03(7) min (minutes) respectively 4.818 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁷Eu	100 %	2.781(6) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁷Pm.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 95) and isobaric (same nucleon number A = 157) with Samarium-157. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 95	Isobar A = 157
55	¹⁵⁰Cs
56	¹⁵¹Ba
57	¹⁵²La
58	¹⁵³Ce	¹⁵⁷Ce
59	¹⁵⁴Pr	¹⁵⁷Pr
60	¹⁵⁵Nd	¹⁵⁷Nd
61	¹⁵⁶Pm	¹⁵⁷Pm
62	¹⁵⁷Sm	¹⁵⁷Sm
63	¹⁵⁸Eu	¹⁵⁷Eu
64	¹⁵⁹Gd	¹⁵⁷Gd
65	¹⁶⁰Tb	¹⁵⁷Tb
66	¹⁶¹Dy	¹⁵⁷Dy
67	¹⁶²Ho	¹⁵⁷Ho
68	¹⁶³Er	¹⁵⁷Er
69	¹⁶⁴Tm	¹⁵⁷Tm
70	¹⁶⁵Yb	¹⁵⁷Yb
71	¹⁶⁶Lu	¹⁵⁷Lu
72	¹⁶⁷Hf	¹⁵⁷Hf
73	¹⁶⁸Ta	¹⁵⁷Ta
74	¹⁶⁹W	¹⁵⁷W
75	¹⁷⁰Re
76	¹⁷¹Os
77	¹⁷²Ir
78	¹⁷³Pt
79	¹⁷⁴Au
80	¹⁷⁵Hg
81	¹⁷⁶Tl