Promethium-155

Properties and data of the isotope ¹⁵⁵Pm.

Content

General data

Name of the isotope:Promethium-155; Pm-155Symbol:¹⁵⁵Pm or 15561PmMass number A:155 (= number of nucleons)Atomic number Z:61 (= number of protons)Neutrons N:94Isotopic mass:154.928137(5) u (atomic weight of Promethium-155)Nuclide mass:154.8946762 u (calculated nuclear mass without electrons)Mass excess:-66.93995 MeVMass defect:1.363692056 u (per nucleus)Nuclear binding energy:1270.27096801 MeV (per nucleus)
8.19529657 MeV (average binding energy per nucleon)Separation energy:S_N = 6.50(5) MeV (first neutron)
S_P = 8.40(5) MeV (first proton)Half-life:41.5(2) sDecay constant λ:0.01670234170024 s^-1Specific activity α:6.53141911750 × 10⁺¹⁹ Bq g^-1
1765248410.1376 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2-Year of discovery:1982

Radioactive Decay

Half-life T_½ = 41.5(2) s respectively 4.15 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁵Sm	100 %	3.251(5) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁵Nd.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 94) and isobaric (same nucleon number A = 155) with Promethium-155. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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