Ion yields from strong optical field ionization experiments using 100-femtosecond laser pulses

Abstract

The ultra•fast ionization of argon, krypton and xenon by intense ultra-short laser pulses is studied. Intensities in the range 1014 to 1016 W/cm2 at a wavelength of 616 nm &e provided by a colliding pulse mode-locked dye laser system. To date, ion yields have been monitored using a 1 meter time.offlight spectrometer. Intensity dependent photoelectron signals are deduced from ion data. In an ultra-fast strong field environment, ionization times can be less than an optical period, affording a better distinction between a field ionization picture and a multiphoton ionization picture. For most cases that we study, Keldysh parameters are below 1, indicating that we are in a field ionization regime. As a laser system under development progresses towards the design goal of 1 joule per 100 femtosecond pulse, we will extend these investigations to peak intensities of order 1018 to 1019 Watts/cmZ.