Resonantly Enhanced Multiphoton Ionization and Third-Harmonic Generation in Xenon Gas

Abstract

Resonantly enhanced multiphoton ionization signals through the $6s[\frac{3}{2}]J=1$ state of Xe rapidly disappear at pressures above 0.30 Torr; concurrently, intense, vacuum-ultra-violet third-harmonic radiation is detected in the forward direction. Laser excitation spectra of the vacuum ultraviolet light exhibit increasing blue shifts and bandwidths with increasing pressure. The observed competition between ionization and third-harmonic generation is discussed in terms of a model involving fast collective emission.