Resonantly enhanced three-photon ionization of krypton

Abstract

The cross section for three-photon ionization of ground-state krypton at \ensuremath{\lambda}=193 nm (ArF laser) has been determined. In these experiments, a microwave-absorption technique provided real-time detection of electrons along with measurements of the absolute electron density. Due to a two-photon resonance with the 6p${[(3/2)]}_{2}$ level, the photoelectron number density was observed to vary quadratically with ArF laser intensity for ${I}_{\mathrm{ArF}}$ beyond 50--100 MW ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ and Kr pressures below 50 Torr.