Promethium-128

Properties and data of the isotope ¹²⁸Pm.

Content

General data

Name of the isotope:Promethium-128; Pm-128Symbol:¹²⁸Pm or 12861PmMass number A:128 (= number of nucleons)Atomic number Z:61 (= number of protons)Neutrons N:67Isotopic mass:127.94870(32) u (atomic weight of Promethium-128)Nuclide mass:127.9152392 u (calculated nuclear mass without electrons)Mass excess:-47.78564 MeVMass defect:1.109176324 u (per nucleus)Nuclear binding energy:1033.19109075 MeV (per nucleus)
8.0718054 MeV (average binding energy per nucleon)Separation energy:S_N = 11.07(50) MeV (first neutron)Half-life:1.0(3) sDecay constant λ:0.69314718055995 s^-1Specific activity α:3.286795242519 × 10⁺²¹ Bq g^-1
88832303851.884 Ci g^-1Spin and parity:
(nuclear angular momentum)5.6.7Year of discovery:1999

Radioactive Decay

Half-life T_½ = 1.0(3) s.

Decay mode	Daughter	Probability	Decay energy
EE/β⁺	¹²⁸Nd	100 %	12.53(36) MeV
α	¹²⁴Pm	?	2.94(50) MeV
EE, p	¹²⁷Pr	?

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 67) and isobaric (same nucleon number A = 128) with Promethium-128. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 67	Isobar A = 128
38	¹⁰⁵Sr
39	¹⁰⁶Y
40	¹⁰⁷Zr
41	¹⁰⁸Nb
42	¹⁰⁹Mo
43	¹¹⁰Tc
44	¹¹¹Ru
45	¹¹²Rh
46	¹¹³Pd	¹²⁸Pd
47	¹¹⁴Ag	¹²⁸Ag
48	¹¹⁵Cd	¹²⁸Cd
49	¹¹⁶In	¹²⁸In
50	¹¹⁷Sn	¹²⁸Sn
51	¹¹⁸Sb	¹²⁸Sb
52	¹¹⁹Te	¹²⁸Te
53	¹²⁰I	¹²⁸I
54	¹²¹Xe	¹²⁸Xe
55	¹²²Cs	¹²⁸Cs
56	¹²³Ba	¹²⁸Ba
57	¹²⁴La	¹²⁸La
58	¹²⁵Ce	¹²⁸Ce
59	¹²⁶Pr	¹²⁸Pr
60	¹²⁷Nd	¹²⁸Nd
61	¹²⁸Pm	¹²⁸Pm
62	¹²⁹Sm	¹²⁸Sm
63	¹³⁰Eu