A Time-dependent study of photoelectron angular distributions due to laser-induced continuum structures

Abstract

The coupling of an atomic continuum to a discrete state by a strong laser field leads to so-called “laser-induced continuum structures” (LICS). In photo-ionization studies, LICS manifest themselves as autoionization-like resonances in various observable quantities. To date only very little is known about vector correlations in the region of LICS: the vast majority of publications deal with integral and angle-independent characteristics. With the advent of bright VUV and soft X-ray radiation sources (free-electron lasers, lasers based upon high-harmonic generation, and next-generation synchrotrons), experimental studies of vector correlations in the region of LICS are becoming feasible. We study the influence of LICS on the angular distribution of photo-electrons in the femtosecond time domain by solving the time-dependent Schrödinger equation directly on a space-time grid. This avoids possible restrictions due to the pulse duration and strength imposed by rotating-wave or adiabatic approximations. As a by-product of our calculations, we also gain access to the motion of the electron cloud, which allows us to visualize the dynamics of the process.