Gold-199m

Properties and data of the isotope ¹⁹⁹Au.

Content

General data

Name of the isotope:Gold-199m; Au-199mSymbol:¹⁹⁹Au or 19979AuMass number A:199 (= number of nucleons)Atomic number Z:79 (= number of protons)Neutrons N:120Isotopic mass:198.9687666(6) u (atomic weight of Gold-199m)
Excitation energy: 548.9405(21) keVNuclide mass:198.9254335 u (calculated nuclear mass without electrons)Mass excess:-29.09372 MeVMass defect:1.689200848 u (per nucleus)Nuclear binding energy:1573.48045471 MeV (per nucleus)
7.90693696 MeV (average binding energy per nucleon)Half-life:0.44(3) msDecay constant λ:1.5753345012726 s^-1Specific activity α:4.791356701101 × 10⁺²¹ Bq g^-1
129496127056.81 Ci g^-1Spin and parity:
(nuclear angular momentum)(11/2)-

Radioactive Decay

Half-life T_½ = 0.44(3) ms respectively 4.4 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹⁹⁹Au	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
¹⁹⁹Au		3.139(7) d	3/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 120) and isobaric (same nucleon number A = 199) with Gold-199m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 120	Isobar A = 199
73	¹⁹³Ta
74	¹⁹⁴W
75	¹⁹⁵Re	¹⁹⁹Re
76	¹⁹⁶Os	¹⁹⁹Os
77	¹⁹⁷Ir	¹⁹⁹Ir
78	¹⁹⁸Pt	¹⁹⁹Pt
79	¹⁹⁹Au	¹⁹⁹Au
80	²⁰⁰Hg	¹⁹⁹Hg
81	²⁰¹Tl	¹⁹⁹Tl
82	²⁰²Pb	¹⁹⁹Pb
83	²⁰³Bi	¹⁹⁹Bi
84	²⁰⁴Po	¹⁹⁹Po
85	²⁰⁵At	¹⁹⁹At
86	²⁰⁶Rn	¹⁹⁹Rn
87	²⁰⁷Fr	¹⁹⁹Fr
88	²⁰⁸Ra
89	²⁰⁹Ac
90	²¹⁰Th