Production of argon metastable atoms in high pressure (20-300 Torr) microwave discharges

Abstract

The production of Ar(3P2) metastable atoms has been determined in high pressure (20-300 Torr) and low power (5-30 W) argon 2.45 GHz microwave discharges. The following plasma parameters have been measured : the gas temperature, deduced from the rotational spectra of CN radical in impurity in argon, was found between 380 K (20 Torr, 5 W) and 840 K (300 Torr, 30 W) ; the Ar (3P2) concentration (n M), measured by the resonant optical absorption method, ranged from 1 to 5 × 1011 cm-3 ; the electron density (n e), measured by the phase variation of the outside electric field, was from 3 to 20 × 1012 cm-3. With a n M/ ne density ratio of 0.065, the 2.45 GHz microwave plasma appears to be a more ionized than excited gas medium