Samarium-156m

Properties and data of the isotope ^156mSm.

Contents

See also: List of individual Samarium isotopes (and general data sources).

General data

Name of the isotope:Samarium-156m; Sm-156mSymbol:^156mSm or 156m62SmMass number A:156 (= number of nucleons)Atomic number Z:62 (= number of protons)Neutrons N:94Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.5161290322581 (= neutron-proton ratio)Neutron excess (N-Z):32Excitation energy:1397.55(9) keVIsotopic mass:155.925539(9) u (atomic weight of Samarium-156m)Nuclide mass:155.8915297 u (calculated nuclear mass without electrons)Mass excess:-69.35997 MeVMass defect:1.374115088 u (per nucleus)Nuclear binding energy:1279.97995978 MeV (per nucleus)
8.20499974 MeV (average binding energy per nucleon)Half-life:185(7) nsDecay constant λ:3746741.5165402 s^-1Specific activity α:1.455703559895 × 10⁺²⁸ Bq g^-1
3.934333945663 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)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
¹⁵⁶Sm		9.4(2) h	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 94) and isobaric (same nucleon number A = 156) with Samarium-156m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 94	Isobar A = 156
54	¹⁴⁸Xe
55	¹⁴⁹Cs
56	¹⁵⁰Ba
57	¹⁵¹La	¹⁵⁶La
58	¹⁵²Ce	¹⁵⁶Ce
59	¹⁵³Pr	¹⁵⁶Pr
60	¹⁵⁴Nd	¹⁵⁶Nd
61	¹⁵⁵Pm	¹⁵⁶Pm
62	¹⁵⁶Sm	¹⁵⁶Sm
63	¹⁵⁷Eu	¹⁵⁶Eu
64	¹⁵⁸Gd	¹⁵⁶Gd
65	¹⁵⁹Tb	¹⁵⁶Tb
66	¹⁶⁰Dy	¹⁵⁶Dy
67	¹⁶¹Ho	¹⁵⁶Ho
68	¹⁶²Er	¹⁵⁶Er
69	¹⁶³Tm	¹⁵⁶Tm
70	¹⁶⁴Yb	¹⁵⁶Yb
71	¹⁶⁵Lu	¹⁵⁶Lu
72	¹⁶⁶Hf	¹⁵⁶Hf
73	¹⁶⁷Ta	¹⁵⁶Ta
74	¹⁶⁸W	¹⁵⁶W
75	¹⁶⁹Re
76	¹⁷⁰Os
77	¹⁷¹Ir
78	¹⁷²Pt
79	¹⁷³Au
80	¹⁷⁴Hg