Osmium-181m

Properties and data of the isotope ¹⁸¹Os.

Content

General data

Name of the isotope:Osmium-181m; Os-181mSymbol:¹⁸¹Os or 18176OsMass number A:181 (= number of nucleons)Atomic number Z:76 (= number of protons)Neutrons N:105Isotopic mass:180.953247(27) u (atomic weight of Osmium-181m)
Excitation energy: 49.20(14) keVNuclide mass:180.9115592 u (calculated nuclear mass without electrons)Mass excess:-43.55014 MeVMass defect:1.551271612 u (per nucleus)Nuclear binding energy:1445.00019895 MeV (per nucleus)
7.98342651 MeV (average binding energy per nucleon)Half-life:2.7(1) minDecay constant λ:0.0042786862997527 s^-1Specific activity α:1.43149175514 × 10⁺¹⁹ Bq g^-1
386889663.55243 Ci g^-1Spin and parity:
(nuclear angular momentum)7/2-

Radioactive Decay

Half-life T_½ = 2.7(1) min (minutes) respectively 1.62 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹⁸¹Re	ca. 97 %
Iso	¹⁸¹Os	≤ 3 %

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
¹⁸¹Os		105(3) min	1/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 105) and isobaric (same nucleon number A = 181) with Osmium-181m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 105	Isobar A = 181
63	¹⁶⁸Eu
64	¹⁶⁹Gd
65	¹⁷⁰Tb
66	¹⁷¹Dy
67	¹⁷²Ho
68	¹⁷³Er
69	¹⁷⁴Tm
70	¹⁷⁵Yb	¹⁸¹Yb
71	¹⁷⁶Lu	¹⁸¹Lu
72	¹⁷⁷Hf	¹⁸¹Hf
73	¹⁷⁸Ta	¹⁸¹Ta
74	¹⁷⁹W	¹⁸¹W
75	¹⁸⁰Re	¹⁸¹Re
76	¹⁸¹Os	¹⁸¹Os
77	¹⁸²Ir	¹⁸¹Ir
78	¹⁸³Pt	¹⁸¹Pt
79	¹⁸⁴Au	¹⁸¹Au
80	¹⁸⁵Hg	¹⁸¹Hg
81	¹⁸⁶Tl	¹⁸¹Tl
82	¹⁸⁷Pb	¹⁸¹Pb
83	¹⁸⁸Bi
84	¹⁸⁹Po
85	¹⁹⁰At