Promethium-157

Properties and data of the isotope ¹⁵⁷Pm.

Contents

General data

Name of the isotope:Promethium-157; Pm-157Symbol:¹⁵⁷Pm or 15761PmMass number A:157 (= number of nucleons)Atomic number Z:61 (= number of protons)Neutrons N:96Isotopic mass:156.933121(8) u (atomic weight of Promethium-157)Nuclide mass:156.8996602 u (calculated nuclear mass without electrons)Mass excess:-62.29739 MeVMass defect:1.376037888 u (per nucleus)Nuclear binding energy:1281.77103644 MeV (per nucleus)
8.16414673 MeV (average binding energy per nucleon)Separation energy:S_N = 6.205(8) MeV (first neutron)
S_P = 9.11(20) MeV (first proton)Half-life:10.56(10) sDecay constant λ:0.065638937553025 s^-1Specific activity α:2.533890563082 × 10⁺²⁰ Bq g^-1
6848352873.1965 Ci g^-1Spin and parity:
(nuclear angular momentum)(5/2-)Year of discovery:1987

Radioactive Decay

Half-life T_½ = 10.56(10) s respectively 1.056 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁷Sm	100 %	4.381(8) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 96) and isobaric (same nucleon number A = 157) with Promethium-157. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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