Abstract

We report on photoionization measurements made using intense 800 nm ultrashort pulse laser light and its high harmonics. First, we present photoelectron kinetic energy spectra showing prominent features at high kinetic energies that cannot be explained by the simpleman/rescattering theory, traditional Rydberg state resonances or other current theoretical treatments. Second, we report the first indications of multiphoton and multiple ionization using high harmonic radiation. We have measured what is believed to be two-photon ionization of both neutral and singly ionized Krypton. Ion charge state distributions for harmonic orders ranging from the 3rd to the 17th are presented for the noble gases.

© 1997 Optical Society of America