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Proton Excitation of the Argon Atom
Phys. Rev. 178, 4 – Published 5 February, 1969
DOI: https://doi.org/10.1103/PhysRev.178.4
Abstract
Studies of the excitation of argon with 4-MeV protons have been carried out by making use of a vacuum ultraviolet scanning monochromator and a 6-MeV Van de Graaff accelerator. Protons were directed through the gas and then into a Faraday cup in an arrangement in which the relative intensity of emitted light could be studied over a wide range of gas pressure (1 to 1500 Torr). Four continua near 2100, 1900, 1300, and 1100 Å, respectively, as well as escape radiation originating from the 1048 Å resonance line, were studied as a function of pressure.
Studies of the intensity of the four main continua (per unit of proton power dissipation) as a function of pressure led us to the conclusion that each continuum has a separate atomic precursor. We suggest that the 1300 Å continuum and the 1100 Å continuum are dissociative diatomic continua and originate from the and the resonance atomic states, respectively. We tentatively suggest that the continua near 2100 Å and near 1900 Å are recombination spectra involving the formation of argon excimers with binding energies of about 4 eV.
The 1300 and 1100 Å continua have been observed in gas discharges, but these were interpreted as a single continuum originating from the state. We believe that the present experimental method, which makes possible gas kinetic observations at spectroscopically defined photon energies, is indeed a powerful tool for the study of atomic and molecular structure and processes.
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