Absorption of CO2laser radiation in an exploded lithium wire plasma

摘要

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‐Å line and line intensity ratios of the same line to the Li II 5485−Å line were used to extract the density and temperature from time‐resolved emission spectra. The neutral density was found from absorption measurements at 6328 Å and compared well with particle conservation calculations. In order to explain the strong observed absorption of both 10.6‐μ and 6328‐Å 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.