Polonium-199m

Properties and data of the isotope ^199mPo.

Contents

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

General data

Name of the isotope:Polonium-199m; Po-199mSymbol:^199mPo or 199m84PoMass number A:199 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:115Isotopic mass:198.983673(19) u (atomic weight of Polonium-199m)
Excitation energy: 310(2) keVNuclide mass:198.9375977 u (calculated nuclear mass without electrons)Mass excess:-15.2085 MeVMass defect:1.670095028 u (per nucleus)Nuclear binding energy:1555.68349801 MeV (per nucleus)
7.81750502 MeV (average binding energy per nucleon)Half-life:4.17(5) minDecay constant λ:0.0027703724243003 s^-1Specific activity α:8.426046956374 × 10⁺¹⁸ Bq g^-1
227730998.82093 Ci g^-1Spin and parity:
(nuclear angular momentum)(13/2+)Magnetic dipole moment:μ(μ_N) = -1.005(70)Quadrupole moment Q:+1.40(35) barn (100 fm²)Nuclear g-factor:g_l = -0.15461538461538

Radioactive Decay

Half-life T_½ = 4.17(5) min (minutes) respectively 2.502 × 10² seconds s.

Decay mode	Daughter	Probability
α	¹⁹⁵Pb	24(1) %
EC/β⁺	¹⁹⁹Bi	73.5(10) %
Iso	¹⁹⁹Po	2.5(10) %

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
¹⁹⁹Po		5.47(15) min	(3/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 115) and isobaric (same nucleon number A = 199) with Polonium-199m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 115	Isobar A = 199
70	¹⁸⁵Yb
71	¹⁸⁶Lu
72	¹⁸⁷Hf
73	¹⁸⁸Ta
74	¹⁸⁹W
75	¹⁹⁰Re	¹⁹⁹Re
76	¹⁹¹Os	¹⁹⁹Os
77	¹⁹²Ir	¹⁹⁹Ir
78	¹⁹³Pt	¹⁹⁹Pt
79	¹⁹⁴Au	¹⁹⁹Au
80	¹⁹⁵Hg	¹⁹⁹Hg
81	¹⁹⁶Tl	¹⁹⁹Tl
82	¹⁹⁷Pb	¹⁹⁹Pb
83	¹⁹⁸Bi	¹⁹⁹Bi
84	¹⁹⁹Po	¹⁹⁹Po
85	²⁰⁰At	¹⁹⁹At
86	²⁰¹Rn	¹⁹⁹Rn
87	²⁰²Fr	¹⁹⁹Fr
88	²⁰³Ra
89	²⁰⁴Ac