ENHANCEMENT OF THE VACUUM-ULTRAVIOLET EMISSION FROM EXCIMER LASER-GENERATED PLASMAS BY AMBIENT GAS ATOMS

We have measured the axial (z) and radial (x) distribution of the vacu um ultraviolet emission from excimer laser generated aluminum plasmas in vacuum and in 300 mTorr of argon. The ratio of the radiated line in tensities (emission in a gas versus vacuum) on the z axis (i.e., x = 0 ) increased exponentially with distance from the target surface for pl asmas generated in a 300 mTorr argon ambient. The absolute line intens ities increased linearly with the argon pressure and approximately lin early with the ambient gas atomic cross section when other rare gases were substituted. The line intensity radial distribution was broader f or plasmas in argon than in vacuum and the magnitude of the effect inc reased monotonically with z. The spectral data obtained from plasmas i n a gas ambient are discussed in terms of the diffusion of plasma elec trons in an ionized gas.