Abstract

The behavior of atoms in strong fields has been the subject of many investigations, both experimental and theoretical. Previously, the majority of experimental studies have been confined to the multi-photon ionization or mixed regimes while few experiments have been done in the tunneling regime[1,2]. The data we will present is the first to examine the photoionization process over the intensity range from multiphoton ionization to well within the tunneling regime. We have taken photoelectron energy spectra, ion yield curves, and angular distributions of helium and neon over a wide range of intensities using a titanium sapphire laser operating at 1 kHz, 780 nm, and a pulse width of ~120 fs, focused into an UHV chamber with f/4 optics, allowing maximum intensities of 20 PW/cm². The large dynamic range allowed by the kilohertz repetition rate makes it possible for a quantitative comparison between experiment and theory. Helium and neon were chosen for the study since previous investigations have established that ionization occurs in the tunneling regime [3]. Our investigations show that while the rescattering model [4,5] describes the one electron dynamics quantitatively, the extension of the rescattering model to inelastic rescattering as a mechanism for creating higher charge states fails to provide even a qualitative description.

© 1997 Optical Society of America