Absorption of CO2 laser radiation in an exploded lithium wire plasma

An absorption experiment was performed with a pulsed TEA CO2 laser incident upon a partially ionized plasma created by exploding a 0.0025-cm-diam lithium wire in vacuum. Stark broadening of the Li I 6104-A line and line intensity ratios of the same line to the Li II 5485-A line were used to extract the density and temperature from time-resolved emission spectra. The neutral density was found from absorption measurements at 6328 A and compared well with particle conservation calculations. In order to explain the strong observed absorption of both 10.6-μ and 6328-A radiation, the plasma was assumed to consist of a hot peripheral region containing electrons and singly ionized lithium ions and a colder central region of excited neutrals. The model was supported by computer calculations and spectroscopic observations. Absorption of the 10.6-μ radiation was dominated by inverse bremsstrahlung in the field of ions and in the presence of neutrals