Emission of Negative Potassium Ions from Single Crystal Potassium Bromide during Exposure to 248-nm Excimer Laser Radiation

Abstract

Many wide bandgap materials yield charged and neutral emissions when exposed to sub-bandgap laser radiation at power densities below the threshold for optical breakdown and plume formation. In previous work, we reported the observation of negative alkali ions from several alkali halides under comparable conditions. Within our detection sensitivity, we observed no negative halogen ion emission, in spite of the high electron affinities of the halogens. Significantly, the positive and negative alkali ions showed a high degree of spatial and temporal overlap. Our conclusion, based on a detailed study of KCl emissions, was that K− is formed by the sequential attachment of two electrons to K+. Here we provide further evidence for this mechanism based on a study of KBr.

Positive ion emission from oxidized aluminum during ultraviolet excimer laser irradiation

“…Thus any relevant change in potential must be sustained for at least 1 ls after the laser pulse. Potential changes confined to the duration of the laser pulse 48 will have very little effect on the ion kinetic energy.…”