Some Studies of the Kinetic State of an Excited Gas Or Plasma Interacting with Radiation

Some basic experimental and theoretical studies relating to the general problems of determining the kinetic state of a gas are described. Specifically, the studies are concerned with deducing the kinetic state from experimentally observed profiles (shapes) and total intensities of spectral lines of a gas. For the experimental studies, a d.c. excited monatomic gas column consisting of Ne20 or Ne22 or a mixture of another inert gas (mainly He4 is employed). The variations with pressure, discharge current, and discharge wall temperature of the absorption profile parameters such as the maximum absorption coefficient, the shift, the width, and the line shape of the profile, are presented. To account for the observed results, line shape theories were developed. The important excitation and de-excitation processes, as well as the effects of some plasma properties, such as the electron number density and electron temperature of the population processes, were assessed. Difficulties of applying such theories to small diameter and low pressure discharges are discussed. Finally, kinetic equations describing the kinetic state of an excited monatomic gas interacting with radiation are developed, taking into account collisional and radiative processes.