Promethium-135m

Properties and data of the isotope ¹³⁵Pm.

Content

General data

Name of the isotope:Promethium-135m; Pm-135mSymbol:¹³⁵Pm or 13561PmMass number A:135 (= number of nucleons)Atomic number Z:61 (= number of protons)Neutrons N:74Isotopic mass:134.92480(8) u (atomic weight of Promethium-135m)
Excitation energy: 68.7+y keVNuclide mass:134.8913392 u (calculated nuclear mass without electrons)Mass excess:-70.04835 MeVMass defect:1.193730736 u (per nucleus)Nuclear binding energy:1111.9530182 MeV (per nucleus)
8.23668902 MeV (average binding energy per nucleon)Half-life:45(4) sDecay constant λ:0.01540327067911 s^-1Specific activity α:6.922437741293 × 10⁺¹⁹ Bq g^-1
1870929119.2685 Ci g^-1Spin and parity:
(nuclear angular momentum)(11/2-)

Radioactive Decay

Half-life T_½ = 45(4) s respectively 4.5 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹³⁵Nd	100 %

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
¹³⁵Pm		49(3) s	(5/2+,3/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 74) and isobaric (same nucleon number A = 135) with Promethium-135m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 74	Isobar A = 135
41	¹¹⁵Nb
42	¹¹⁶Mo
43	¹¹⁷Tc
44	¹¹⁸Ru
45	¹¹⁹Rh
46	¹²⁰Pd
47	¹²¹Ag
48	¹²²Cd
49	¹²³In	¹³⁵In
50	¹²⁴Sn	¹³⁵Sn
51	¹²⁵Sb	¹³⁵Sb
52	¹²⁶Te	¹³⁵Te
53	¹²⁷I	¹³⁵I
54	¹²⁸Xe	¹³⁵Xe
55	¹²⁹Cs	¹³⁵Cs
56	¹³⁰Ba	¹³⁵Ba
57	¹³¹La	¹³⁵La
58	¹³²Ce	¹³⁵Ce
59	¹³³Pr	¹³⁵Pr
60	¹³⁴Nd	¹³⁵Nd
61	¹³⁵Pm	¹³⁵Pm
62	¹³⁶Sm	¹³⁵Sm
63	¹³⁷Eu	¹³⁵Eu
64	¹³⁸Gd	¹³⁵Gd
65	¹³⁹Tb	¹³⁵Tb
66	¹⁴⁰Dy
67	¹⁴¹Ho