Mercury-201m

Properties and data of the isotope ^201mHg.

Contents

Mercury-201m is an excited nuclear state of the nuclide ²⁰¹Hg, characterized by a defined excitation energy (766,22 keV). Its spin and parity quantum numbers differ from those of the ground state (gs). Simultaneously, this metastable nuclear isomer possesses an independent, experimentally measurable lifetime: decay occurs via an isomeric transition to Hg-201 Ground state with a half-life of approximately 94 microseconds.

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

General data

Name of the isotope:Mercury-201m; Hg-201mSymbol:^201mHg or 201m80HgMass number A:201 (= number of nucleons)Atomic number Z:80 (= number of protons)Neutrons N:121Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.5125 (= neutron-proton ratio)Neutron excess (N-Z):41Excitation energy:766.22(15) keVIsotopic mass:200.9703031(8) u (atomic weight of Mercury-201m)Nuclide mass:200.9264215 u (calculated nuclear mass without electrons)Mass excess:-27.66248 MeVMass defect:1.704154296 u (per nucleus)Nuclear binding energy:1587.4095018 MeV (per nucleus)
7.89755971 MeV (average binding energy per nucleon)Half-life:94(2) μsDecay constant λ:7373.9061761696 s^-1Specific activity α:2.220335084042 × 10⁺²⁵ Bq g^-1
6.000905632547 × 10⁺¹⁴ Ci g^-1Spin and parity:
(nuclear angular momentum)13/2+Year of discovery:1961

Radioactive Decay

Half-life T_½ = 94(2) μs respectively 9.4 × 10^-5 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	²⁰¹Hg	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
²⁰¹Hg		stable	3/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 121) and isobaric (same nucleon number A = 201) with Mercury-201m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 121	Isobar A = 201
73	¹⁹⁴Ta
74	¹⁹⁵W
75	¹⁹⁶Re
76	¹⁹⁷Os	²⁰¹Os
77	¹⁹⁸Ir	²⁰¹Ir
78	¹⁹⁹Pt	²⁰¹Pt
79	²⁰⁰Au	²⁰¹Au
80	²⁰¹Hg	²⁰¹Hg
81	²⁰²Tl	²⁰¹Tl
82	²⁰³Pb	²⁰¹Pb
83	²⁰⁴Bi	²⁰¹Bi
84	²⁰⁵Po	²⁰¹Po
85	²⁰⁶At	²⁰¹At
86	²⁰⁷Rn	²⁰¹Rn
87	²⁰⁸Fr	²⁰¹Fr
88	²⁰⁹Ra	²⁰¹Ra
89	²¹⁰Ac
90	²¹¹Th
91	²¹²Pa