Argon-32

Properties and data of the isotope ³²Ar.

Contents

Argon-32 is a radioisotope of the chemical element argon, which has 14 neutrons in its atomic nucleus in addition to the element-specific 18 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 32. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ³²Ar is exclusively for academic purposes.

The radioactive isotope was first observed - according to a report from 1977 - as a product of the spallation reaction when a vanadium template was bombarded with protons of an energy of 600 MeV [1].

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

General data

Name of the isotope:Argon-32; Ar-32Symbol:³²Ar or 3218ArMass number A:32 (= number of nucleons)Atomic number Z:18 (= number of protons)Neutrons N:14Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):0.77777777777778 (= neutron-proton ratio)Neutron excess (N-Z):-4Isotopic mass:31.9976378(19) u (atomic weight of Argon-32)Nuclide mass:31.9877635 u (calculated nuclear mass without electrons)Mass excess:-2.20038 MeVMass defect:0.2645216 u (per nucleus)Nuclear binding energy:246.40028327 MeV (per nucleus)
7.70000885 MeV (average binding energy per nucleon)Separation energy:S_N = 21.597(200) MeV (first neutron)
S_P = 2.455(4) MeV (first proton)Half-life:98(2) msDecay constant λ:7.072930413877 s^-1Specific activity α:1.331166469358 × 10⁺²³ Bq g^-1
3597747214483.5 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:3.3468(62) femtometer fmMirror nucleus:Silicon-32Year of discovery:1977

Radioactive Decay

Half-life T_½ = 98(2) ms respectively 9.8 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	³²Cl	64.42(22) %	11.1344(19) MeV
β⁺ p	³¹S	35.58(22) %	9.555 MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 14) and isobaric (same nucleon number A = 32) with Argon-32. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 14	Isobar A = 32
5	¹⁹B
6	²⁰C
7	²¹N
8	²²O
9	²³F
10	²⁴Ne	³²Ne
11	²⁵Na	³²Na
12	²⁶Mg	³²Mg
13	²⁷Al	³²Al
14	²⁸Si	³²Si
15	²⁹P	³²P
16	³⁰S	³²S
17	³¹Cl	³²Cl
18	³²Ar	³²Ar
19	³³K	³²K
20	³⁴Ca

External data and identifiers

Adopted Levels, Gammas:NuDat 32Ar

Literature and References

[1] - E. Hagberg, P. G. Hansen, J. C. Hardy et al.:
Decay of a T_z = -2 Nucleus: Argon-32.
In: Physical Review Letters, 39, 792, (1977), DOI 10.1103/PhysRevLett.39.792.

[2] - B. Blank et al.:
Detailed study of the decay of ³²Ar.
In: The European Physical Journal A, 57, 28, (2021), DOI 10.1140/epja/s10050-020-00341-3.