Polonium-209m

Properties and data of the isotope ^209mPo.

Contents

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

General data

Name of the isotope:Polonium-209m; Po-209nSymbol:^209mPo or 209m84PoMass number A:209 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:125Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.4880952380952 (= neutron-proton ratio)Neutron excess (N-Z):41Excitation energy:4265.4(3) keVIsotopic mass:208.9824304(19) u (atomic weight of Polonium-209m)Nuclide mass:208.9363551 u (calculated nuclear mass without electrons)Mass excess:-16.36598 MeVMass defect:1.757986788 u (per nucleus)Nuclear binding energy:1637.5541451 MeV (per nucleus)
7.8351873 MeV (average binding energy per nucleon)Half-life:119(4) nsDecay constant λ:5824766.2231928 s^-1Specific activity α:1.686421282320 × 10⁺²⁸ Bq g^-1
4.557895357623 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)31/2-Magnetic dipole moment:μ(μ_N) = 9.68(8)Nuclear g-factor:g_l = 0.62451612903226Year of discovery:1974

Radioactive Decay

Half-life T_½ = 119(4) ns respectively 1.19 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	²⁰⁹Po	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
²⁰⁹Po		124(3) a	1/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 125) and isobaric (same nucleon number A = 209) with Polonium-209m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 125	Isobar A = 209
76	²⁰¹Os
77	²⁰²Ir
78	²⁰³Pt
79	²⁰⁴Au	²⁰⁹Au
80	²⁰⁵Hg	²⁰⁹Hg
81	²⁰⁶Tl	²⁰⁹Tl
82	²⁰⁷Pb	²⁰⁹Pb
83	²⁰⁸Bi	²⁰⁹Bi
84	²⁰⁹Po	²⁰⁹Po
85	²¹⁰At	²⁰⁹At
86	²¹¹Rn	²⁰⁹Rn
87	²¹²Fr	²⁰⁹Fr
88	²¹³Ra	²⁰⁹Ra
89	²¹⁴Ac	²⁰⁹Ac
90	²¹⁵Th	²⁰⁹Th
91	²¹⁶Pa
92	²¹⁷U