NONLOCAL THERMODYNAMIC-EQUILIBRIUM IN LASER-SUSTAINED PLASMAS

An argon laser-sustained plasma at atmospheric pressure has been studi ed spectroscopically and the existence of a nonlocal thermodynamic equ ilibrium state has been determined. The spectroscopic data consist of argon-neutral and -ion line emissions used to spatially resolve electr onic energy level population densities in each plasma species. A hydro gen seed is added to the argon flow for the purpose of determining ele ctron number density by Stark broadening analysis of the Balmer series alpha line. Electron and heavy particle kinetic temperatures are calc ulated through the use of an appropriate nonequilibrium model. The dom inant nonequilibrium effect in this plasma is kinetic nonequilibrium w here the electron kinetic temperature can be more than twice the heavy particle kinetic temperature in high laser power flux regions. Typica l electron and heavy particle kinetic temperatures are 14,000 K and 80 00 K, respectively. Electron number density ranges from 6 x 10(16) cm( -3) to 2.1 x 10(17) cm(-3).