Thallium-199m

Properties and data of the isotope ^199mTl.

Contents

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

General data

Name of the isotope:Thallium-199m; Tl-199mSymbol:^199mTl or 199m81TlMass number A:199 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:118Isotopic mass:198.96988(3) u (atomic weight of Thallium-199m)
Excitation energy: 748.87(6) keVNuclide mass:198.92545 u (calculated nuclear mass without electrons)Mass excess:-28.0566 MeVMass defect:1.68640768 u (per nucleus)Nuclear binding energy:1570.87863547 MeV (per nucleus)
7.89386249 MeV (average binding energy per nucleon)Half-life:28.4(2) msDecay constant λ:24.406590864787 s^-1Specific activity α:7.423228691848 × 10⁺²² Bq g^-1
2006278024823.8 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-

Radioactive Decay

Half-life T_½ = 28.4(2) ms respectively 2.84 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹⁹⁹Tl	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
¹⁹⁹Tl		7.42(8) h	1/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 118) and isobaric (same nucleon number A = 199) with Thallium-199m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 118	Isobar A = 199
72	¹⁹⁰Hf
73	¹⁹¹Ta
74	¹⁹²W
75	¹⁹³Re	¹⁹⁹Re
76	¹⁹⁴Os	¹⁹⁹Os
77	¹⁹⁵Ir	¹⁹⁹Ir
78	¹⁹⁶Pt	¹⁹⁹Pt
79	¹⁹⁷Au	¹⁹⁹Au
80	¹⁹⁸Hg	¹⁹⁹Hg
81	¹⁹⁹Tl	¹⁹⁹Tl
82	²⁰⁰Pb	¹⁹⁹Pb
83	²⁰¹Bi	¹⁹⁹Bi
84	²⁰²Po	¹⁹⁹Po
85	²⁰³At	¹⁹⁹At
86	²⁰⁴Rn	¹⁹⁹Rn
87	²⁰⁵Fr	¹⁹⁹Fr
88	²⁰⁶Ra
89	²⁰⁷Ac
90	²⁰⁸Th