Samarium-158

Properties and data of the isotope ¹⁵⁸Sm.

Content

General data

Name of the isotope:Samarium-158; Sm-158Symbol:¹⁵⁸Sm or 15862SmMass number A:158 (= number of nucleons)Atomic number Z:62 (= number of protons)Neutrons N:96Isotopic mass:157.929951(5) u (atomic weight of Samarium-158)Nuclide mass:157.8959417 u (calculated nuclear mass without electrons)Mass excess:-65.25022 MeVMass defect:1.38703292 u (per nucleus)Nuclear binding energy:1292.01284278 MeV (per nucleus)
8.17729647 MeV (average binding energy per nucleon)Separation energy:S_N = 6.644(7) MeV (first neutron)
S_P = 10.242(9) MeV (first proton)Half-life:5.30(3) minDecay constant λ:0.0021797081149684 s^-1Specific activity α:8.360833950246 × 10⁺¹⁸ Bq g^-1
225968485.14179 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1970

Radioactive Decay

Half-life T_½ = 5.30(3) min (minutes) respectively 3.18 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁸Eu	100 %	2.005(10) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁸Pm.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 96) and isobaric (same nucleon number A = 158) with Samarium-158. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 96	Isobar A = 158
55	¹⁵¹Cs
56	¹⁵²Ba
57	¹⁵³La
58	¹⁵⁴Ce
59	¹⁵⁵Pr	¹⁵⁸Pr
60	¹⁵⁶Nd	¹⁵⁸Nd
61	¹⁵⁷Pm	¹⁵⁸Pm
62	¹⁵⁸Sm	¹⁵⁸Sm
63	¹⁵⁹Eu	¹⁵⁸Eu
64	¹⁶⁰Gd	¹⁵⁸Gd
65	¹⁶¹Tb	¹⁵⁸Tb
66	¹⁶²Dy	¹⁵⁸Dy
67	¹⁶³Ho	¹⁵⁸Ho
68	¹⁶⁴Er	¹⁵⁸Er
69	¹⁶⁵Tm	¹⁵⁸Tm
70	¹⁶⁶Yb	¹⁵⁸Yb
71	¹⁶⁷Lu	¹⁵⁸Lu
72	¹⁶⁸Hf	¹⁵⁸Hf
73	¹⁶⁹Ta	¹⁵⁸Ta
74	¹⁷⁰W	¹⁵⁸W
75	¹⁷¹Re
76	¹⁷²Os
77	¹⁷³Ir
78	¹⁷⁴Pt
79	¹⁷⁵Au
80	¹⁷⁶Hg
81	¹⁷⁷Tl
82	¹⁷⁸Pb