Abstract

We have observed for the first time higher order multiphoton resonances in xenon. The clear evolution through parity-allowed resonances at the 8- and subsequent 9-photon level demonstrates the validity of the transient resonance model up to the saturation intensity. At high laser intensities (> 10¹² W/cm²) the ionization limit and high lying Rydberg states of xenon shift ponderomotively upward and ionization occurs via transient resonances with specific multiples of the incident photons [1]. We have observed a very clear evolution of transient 8-photon resonances showing the successive appearance of Rydberg states and a large enhancement in photoelectron signal when reaching the higher order 9-photon resonances. This observation furthers our understanding of the fundamental ionization process in strong fields.

© 1997 Optical Society of America