Thorium-215m

Properties and data of the isotope ²¹⁵Th.

Content

General data

Name of the isotope:Thorium-215m; Th-215mSymbol:²¹⁵Th or 21590ThMass number A:215 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:125Isotopic mass:215.011725(9) u (atomic weight of Thorium-215m)
Excitation energy: 1421.3+x keVNuclide mass:214.9623592 u (calculated nuclear mass without electrons)Mass excess:10.92177 MeVMass defect:1.77564238 u (per nucleus)Nuclear binding energy:1654.00022312 MeV (per nucleus)
7.69302429 MeV (average binding energy per nucleon)Half-life:0.77(6) μsDecay constant λ:900191.14358434 s^-1Specific activity α:2.521431566294 × 10⁺²⁷ Bq g^-1
6.814679908903 × 10⁺¹⁶ Ci g^-1Spin and parity:
(nuclear angular momentum)

Radioactive Decay

Half-life T_½ = 0.77(6) μs respectively 7.7 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	²¹⁵Th	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
²¹⁵Th		1.2(2) s	(1/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 125) and isobaric (same nucleon number A = 215) with Thorium-215m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 125	Isobar A = 215
76	²⁰¹Os
77	²⁰²Ir
78	²⁰³Pt
79	²⁰⁴Au
80	²⁰⁵Hg	²¹⁵Hg
81	²⁰⁶Tl	²¹⁵Tl
82	²⁰⁷Pb	²¹⁵Pb
83	²⁰⁸Bi	²¹⁵Bi
84	²⁰⁹Po	²¹⁵Po
85	²¹⁰At	²¹⁵At
86	²¹¹Rn	²¹⁵Rn
87	²¹²Fr	²¹⁵Fr
88	²¹³Ra	²¹⁵Ra
89	²¹⁴Ac	²¹⁵Ac
90	²¹⁵Th	²¹⁵Th
91	²¹⁶Pa	²¹⁵Pa
92	²¹⁷U	²¹⁵U