Argon-44

Properties and data of the isotope ⁴⁴Ar.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Argon-44 is a radioisotope of the chemical element argon, which has 26 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 44.

The discovery of the radioactive isotope was reported in 1969 [1]; calcium oxide enriched with 97.16% calcium-48 was irradiated with bremsstrahlung at endpoint energies of 39, 46 and 55 MeV, producing argon-44 according to the following photonuclear reaction:

⁴⁸Ca(γ,α)⁴⁴Ar.

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

General data

Name of the isotope:Argon-44; Ar-44Symbol:⁴⁴Ar or 4418ArMass number A:44 (= number of nucleons)Atomic number Z:18 (= number of protons)Neutrons N:26Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.4444444444444 (= neutron-proton ratio)Neutron excess (N-Z):8Isotopic mass:43.9649238(17) u (atomic weight of Argon-44)Nuclide mass:43.9550495 u (calculated nuclear mass without electrons)Mass excess:-32.67327 MeVMass defect:0.401214592 u (per nucleus)Nuclear binding energy:373.72898516 MeV (per nucleus)
8.49384057 MeV (average binding energy per nucleon)Separation energy:S_N = 8.735(6) MeV (first neutron)
S_P = 15.803(62) MeV (first proton)Half-life:11.87(5) minDecay constant λ:0.00097324793675926 s^-1Specific activity α:1.363031666699 × 10⁺¹⁹ Bq g^-1
368386936.94576 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:3.4454(46) femtometer fmYear of discovery:1969

Radioactive Decay

Half-life T_½ = 11.87(5) min (minutes) respectively 7.122 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁴⁴K	100 %	3.1082(16) MeV

Parent Nuclides

Direct parent isotopes are: ⁴⁴Cl, ⁴⁵Cl.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 26) and isobaric (same nucleon number A = 44) with Argon-44. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 26	Isobar A = 44
11	³⁷Na
12	³⁸Mg
13	³⁹Al
14	⁴⁰Si	⁴⁴Si
15	⁴¹P	⁴⁴P
16	⁴²S	⁴⁴S
17	⁴³Cl	⁴⁴Cl
18	⁴⁴Ar	⁴⁴Ar
19	⁴⁵K	⁴⁴K
20	⁴⁶Ca	⁴⁴Ca
21	⁴⁷Sc	⁴⁴Sc
22	⁴⁸Ti	⁴⁴Ti
23	⁴⁹V	⁴⁴V
24	⁵⁰Cr	⁴⁴Cr
25	⁵¹Mn	⁴⁴Mn
26	⁵²Fe
27	⁵³Co
28	⁵⁴Ni
29	⁵⁵Cu
30	⁵⁶Zn