Thallium-191m

Properties and data of the isotope ^191mTl.

Contents

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

General data

Name of the isotope:Thallium-191m; Tl-191mSymbol:^191mTl or 191m81TlMass number A:191 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:110Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.358024691358 (= neutron-proton ratio)Neutron excess (N-Z):29Excitation energy:+x keVIsotopic mass:190.971784(8) u (atomic weight of Thallium-191m)Nuclide mass:190.927354 u (calculated nuclear mass without electrons)Mass excess:-26.28303 MeVMass defect:1.615184352 u (per nucleus)Nuclear binding energy:1504.53453278 MeV (per nucleus)
7.87714415 MeV (average binding energy per nucleon)Half-life:5.22(16) minDecay constant λ:0.0022131136033204 s^-1Specific activity α:7.014569399072 × 10⁺¹⁸ Bq g^-1
189582956.73169 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2(-)

Radioactive Decay

Half-life T_½ = 5.22(16) min (minutes) respectively 3.132 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC	¹⁹¹Hg	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
¹⁹¹Tl			(1/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 110) and isobaric (same nucleon number A = 191) with Thallium-191m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 110	Isobar A = 191
69	¹⁷⁹Tm
70	¹⁸⁰Yb
71	¹⁸¹Lu
72	¹⁸²Hf
73	¹⁸³Ta	¹⁹¹Ta
74	¹⁸⁴W	¹⁹¹W
75	¹⁸⁵Re	¹⁹¹Re
76	¹⁸⁶Os	¹⁹¹Os
77	¹⁸⁷Ir	¹⁹¹Ir
78	¹⁸⁸Pt	¹⁹¹Pt
79	¹⁸⁹Au	¹⁹¹Au
80	¹⁹⁰Hg	¹⁹¹Hg
81	¹⁹¹Tl	¹⁹¹Tl
82	¹⁹²Pb	¹⁹¹Pb
83	¹⁹³Bi	¹⁹¹Bi
84	¹⁹⁴Po	¹⁹¹Po
85	¹⁹⁵At	¹⁹¹At
86	¹⁹⁶Rn