Thallium-185m

Properties and data of the isotope ^185mTl.

Contents

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

General data

Name of the isotope:Thallium-185m; Tl-185mSymbol:^185mTl or 185m81TlMass number A:185 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:104Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.283950617284 (= neutron-proton ratio)Neutron excess (N-Z):23Excitation energy:454.8(15) keVIsotopic mass:184.978789(22) u (atomic weight of Thallium-185m)Nuclide mass:184.934359 u (calculated nuclear mass without electrons)Mass excess:-19.75792 MeVMass defect:1.556189856 u (per nucleus)Nuclear binding energy:1449.58151372 MeV (per nucleus)
7.83557575 MeV (average binding energy per nucleon)Half-life:1.93(8) sDecay constant λ:0.35914361687044 s^-1Specific activity α:1.175442092250 × 10⁺²¹ Bq g^-1
31768705195.959 Ci g^-1Spin and parity:
(nuclear angular momentum)(9/2-)

Radioactive Decay

Half-life T_½ = 1.93(8) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁸¹Au	?
Iso	¹⁸⁵Tl	?

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
¹⁸⁵Tl		19.5(5) s	(1/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 104) and isobaric (same nucleon number A = 185) with Thallium-185m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 104	Isobar A = 185
62	¹⁶⁶Sm
63	¹⁶⁷Eu
64	¹⁶⁸Gd
65	¹⁶⁹Tb
66	¹⁷⁰Dy
67	¹⁷¹Ho
68	¹⁷²Er
69	¹⁷³Tm
70	¹⁷⁴Yb	¹⁸⁵Yb
71	¹⁷⁵Lu	¹⁸⁵Lu
72	¹⁷⁶Hf	¹⁸⁵Hf
73	¹⁷⁷Ta	¹⁸⁵Ta
74	¹⁷⁸W	¹⁸⁵W
75	¹⁷⁹Re	¹⁸⁵Re
76	¹⁸⁰Os	¹⁸⁵Os
77	¹⁸¹Ir	¹⁸⁵Ir
78	¹⁸²Pt	¹⁸⁵Pt
79	¹⁸³Au	¹⁸⁵Au
80	¹⁸⁴Hg	¹⁸⁵Hg
81	¹⁸⁵Tl	¹⁸⁵Tl
82	¹⁸⁶Pb	¹⁸⁵Pb
83	¹⁸⁷Bi	¹⁸⁵Bi
84	¹⁸⁸Po
85	¹⁸⁹At