Promethium-146

Properties and data of the isotope ¹⁴⁶Pm.

Contents

Promethium-146 is a gamma-radiation-emitting radioisotope of the chemical element promethium, which has 85 neutrons in its atomic nucleus in addition to the element-specific 61 protons, resulting in a mass number of 146. This very short-lived, artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁴⁶Pm is for academic purposes only.

The radioactive isotope, which does not occur in natural decay chains, can be produced in nuclear reactors from enriched neodymium-146: ¹⁴⁶Nd(p,n)¹⁴⁶Pm [1].

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

General data

Name of the isotope:Promethium-146; Pm-146Symbol:¹⁴⁶Pm or 14661PmMass number A:146 (= number of nucleons)Atomic number Z:61 (= number of protons)Neutrons N:85Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.3934426229508 (= neutron-proton ratio)Neutron excess (N-Z):24Isotopic mass:145.914702(5) u (atomic weight of Promethium-146)Nuclide mass:145.8812412 u (calculated nuclear mass without electrons)Mass excess:-79.45458 MeVMass defect:1.299142812 u (per nucleus)Nuclear binding energy:1210.14373452 MeV (per nucleus)
8.28865572 MeV (average binding energy per nucleon)Separation energy:S_N = 6.258(5) MeV (first neutron)
S_P = 5.311(4) MeV (first proton)Half-life:5.53(5) aDecay constant λ:3.974695685302 × 10^-9 s^-1Specific activity α:16507708477432 Bq g^-1
446.15428317384 Ci g^-1Spin and parity:
(nuclear angular momentum)3-Year of discovery:1960

Radioactive Decay

Half-life T_½ = 5.53(5) a respectively 1.7439 × 10⁸ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC	¹⁴⁶Nd	65.7(15) %	1.472(4) MeV	453.83(15) keV [I = 64.7(15) %] 735.90(19) keV [I = 22.9(15) %]
β^-	¹⁴⁶Sm	34.3(15) %	1.542(3) MeV	747.24(20) keV [I = 34.1(15) %]

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 85) and isobaric (same nucleon number A = 146) with Promethium-146. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 85	Isobar A = 146
47	¹³²Ag
48	¹³³Cd
49	¹³⁴In
50	¹³⁵Sn
51	¹³⁶Sb
52	¹³⁷Te
53	¹³⁸I
54	¹³⁹Xe	¹⁴⁶Xe
55	¹⁴⁰Cs	¹⁴⁶Cs
56	¹⁴¹Ba	¹⁴⁶Ba
57	¹⁴²La	¹⁴⁶La
58	¹⁴³Ce	¹⁴⁶Ce
59	¹⁴⁴Pr	¹⁴⁶Pr
60	¹⁴⁵Nd	¹⁴⁶Nd
61	¹⁴⁶Pm	¹⁴⁶Pm
62	¹⁴⁷Sm	¹⁴⁶Sm
63	¹⁴⁸Eu	¹⁴⁶Eu
64	¹⁴⁹Gd	¹⁴⁶Gd
65	¹⁵⁰Tb	¹⁴⁶Tb
66	¹⁵¹Dy	¹⁴⁶Dy
67	¹⁵²Ho	¹⁴⁶Ho
68	¹⁵³Er	¹⁴⁶Er
69	¹⁵⁴Tm	¹⁴⁶Tm
70	¹⁵⁵Yb
71	¹⁵⁶Lu
72	¹⁵⁷Hf
73	¹⁵⁸Ta
74	¹⁵⁹W
75	¹⁶⁰Re
76	¹⁶¹Os

External data and identifiers

Adopted Levels, Gammas:NuDat 146Pm

Literature and References

[1] - L. R. Bunney, E. M. Scadden:
Decay characteristics of ¹⁴⁶Pm.
In: Journal of Inorganic and Nuclear Chemistry, (1967), DOI 10.1016/0022-1902(67)80175-1.