The mandatory condition for efficient operation of an optically-pumped all-rare-gas laser (OPRGL) is the presence of rare gas metastable atoms in the discharge plasma with number density of the order of 10<sup>12</sup>-10<sup>13</sup> cm<sup>-3</sup>. This requirement mainly depends on the choice of a discharge system. In this study the number density values of argon metastable atoms were obtained in the condition of the dielectric-barrier discharge (DBD) at an atmospheric pressure.
This paper describes systematic measurements of pressure broadening coefficients for argon and krypton lines in an RF (radio-frequency) discharge plasma sustained in a mixture of inert gases. Using tunable diode laser spectroscopy we obtained experimental data for pressure broadening of argon and krypton lines. Pressure broadening coefficients were determined for Ar+Ne and Kr+Ne and Kr+Ar. For krypton, the isotopic structure of the line was taken into account and an appropriate fitting function was used to determine pressure broadening coefficients for the natural mixture of isotopes. These data may be used for diagnostics of the active medium of optically pumped all-rare-gas lasers.
Absorption spectroscopy measurements of long-lived metastable argon atoms Ar* in a low-pressure RF-discharge were carried out to measure gas leaks in a vacuum chamber. Argon as a carrier gas was flowing through the test chamber and the discharge cell at a rate of 55 μmol/s. If a leak occurs, the ambient air is admixed to the carrier gas flowing through the test chamber. The presence of air in the carrier gas flowing through the discharge plasma produced a decrease in the number density of Ar*, which was measured by means of diode laser absorption spectroscopy. This is because the lifetime of atoms is limited by losses due to collisions with air molecules. The leak-rate of the ambient air ranged from 0.14 to 0.95 μmol/s was measured by a mass flow meter and compared with the amplitude of the absorption signal.