Argon-40 (⁴⁰Ar)

Data nuklida

Unsur

Argon (Ar, Z = 18)

Nomor massa (A)

40

Proton (Z)

18

Neutron (N)

22

Massa atom

39.96238312204 ± 0.00000000234 u

Waktu paruh

Stabil

Mode peluruhan

Tidak meluruh

Kelimpahan alami

[0.936, 1.000]

Tahun penemuan

1920

Sumber data

IAEA Atomic Mass Data Center (NUBASE) and IUPAC CIAAW, via PubChem

Kegunaan isotop argon

• Argon’s chemically inert properties and three stable isotopes make it an ideal tracer of Earth processes,,,,,,,,,,,. Measurements and models of the isotope-amount ratio n(40Ar)/n(36Ar) can provide insights about the evolution of the atmosphere and orogenic (mountain-building) history of the Earth. The comparison of results from potassium-argon and n(40Ar)/n(39Ar) isotope-amount-ratio dating methods with results from other dating methods has been used to study temperature histories of rocks through differences in apparent ages caused by excess argon or partial argon gas loss. The isotope-amount ratio n(40Ar)/n(36Ar) of dissolved argon in groundwater can provide hydrologic information, such as rates of crustal degassing and relative groundwater age. 38Ar produced by cosmic-ray bombardment of rocks and soils at Earth’s surface can provide information about surface exposure history and erosion rate.
• Argon isotopes are used to date rock samples, especially volcanic rocks, using two related techniques (Fig. IUPAC.18.1),,,. –The first technique is potassium-argon dating (K-Ar), which is based on the decay of radioactive 40K to stable 40Ar. By comparing the concentrations of potassium and 40Ar in a sample, it is possible to determine how long the sample has been accumulating radiogenic 40Ar to determine the “age” of the sample. The half-life of 40K is approximately 1.25×109 years, making this a useful tool for dating rocks range in age from about 106 to 109 years. –A modification of the potassium-argon dating technique is the n(40Ar)/n(39Ar) isotope-amount-ratio technique, in which a sample is irradiated in a nuclear reactor to produce 39Ar from 39K. The isotope-amount ratio n(40Ar)/n(39Ar) is then determined, and from this, the approximate age of the rock can be calculated (Fig. IUPAC.18.2). The study of 37Ar (half-life of 35 days), 39Ar (half-life of 268 years), and 40Ar concentrations in groundwater can provide information about the production and release of these isotopes from rocks and other sources into groundwater and the relative ages of different groundwaters,,,,,.
• 38K (half-life of 7.6 min), which is produced by the reactions 38Ar (p, n) 38K and 40Ar (n, 3n) 38K, is a widely used blood-flow tracer. Because 38Ar is more expensive, 40Ar, which also offers many additional advantages as a target, is more commonly used to produce 38K for medical purposes,. 41Ar (half-life of 1.82 h) is used as an industrial gas-flow tracer to help track the movement of gases because its inert properties, half-life, and gamma radiation make it well suited for this purpose.

Reaksi inti

• Penangkapan elektron kalium-40

Isotop argon lainnya

²⁹Ar, ³⁰Ar, ³¹Ar, ³²Ar, ³³Ar, ³⁴Ar, ³⁵Ar, ³⁶Ar, ³⁷Ar, ³⁸Ar, ³⁹Ar, ⁴¹Ar, ⁴²Ar, ⁴³Ar, ⁴⁴Ar, ⁴⁵Ar, ⁴⁶Ar, ⁴⁷Ar, ⁴⁸Ar, ⁴⁹Ar, ⁵⁰Ar, ⁵¹Ar, ⁵²Ar, ⁵³Ar, ⁵⁴Ar

Pelajari

Kimia inti Simulasi peluruhan ⁴⁰Ar Bagan nuklida