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Americium-239

Properties and data of the isotope 239Am.

 

Americium-239 is the radioisotope of the element Americium, whose atomic nucleus has 144 neutrons in addition to the element-specific 95 protons, resulting in a mass number of 239: 239 Am.

See also: list of Americium isotopes.

 

General data

Name of the isotope:Americium-239; Am-239Symbol:239AmMass number A:239Atomic number Z:95 (= number of protons)Neutrons N:144Isotopic mass:239.0530228(21) u (atomic weight of Americium-239)Nuclide mass:239.0009149 u (calculated nuclear mass without electrons)Mass excess:49.39042 MeVMass defect:1.938103144 u (per nucleus)Nuclear binding energy:1805.33145002 MeV (per nucleus)
7.55368808 MeV (average binding energy per nucleon)
Separation energy:SN = 7.10(5) MeV (first neutron)
SP = 4.0618(17) MeV (first proton)
Half-life:11.9(1) hDecay constant λ:1.617990617553 × 10-5 s-1Spin and parity:(5/2)-Year of discovery:1948

 

Radioactive Decay

Half-life T½ = 11.9(1) h (hours) respectively 4.2840 × 104 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
(intensity)
α235Np0,010(1) %5,9224(14) MeV
EE239Pu99,990(1) %0,801(23) MeV

 

Americium-239 radioactive decay chain

 

Parent Nuclides

Direct parent isotopes are: 239Cm, 243Bk.

 

Radiation Protection

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Americium-239 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:Am-239Exemption level:106 BqExemption level per gram:100 Bq/g
Unrestricted handling of solids and liquids.
Half-life:11.9 h

 

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear IsomerExcitation EnergyHalf-lifeSpin
239mAm2500 keV163(12) ns(7/2+)

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 144) and isobaric (same nucleon number A = 239) with Americium-239. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

OZIsotone N = 144Isobar A = 239
85229At
86230Rn
87231Fr
88232Ra
89233Ac
90234Th
91235Pa239Pa
92236U239U
93237Np239Np
94238Pu239Pu
95239Am239Am
96240Cm239Cm
97241Bk239Bk
98242Cf239Cf
99243Es
100244Fm
101245Md

 

External data and identifiers

CAS:16652-10-1InChI Key:LXQXZNRPTYVCNG-AHCXROLUSA-NSMILES:[239Am]PubChem:ID 167554Adopted Levels, Gammas:NuDat 239Am

 


Category: Isotopes

Last update: 26.11.2022



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