Strong Field and Ultrafast Atomic and Molecular Processes

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

This project focuses on understanding theoretically the interaction of intense coherent radiation with atoms and molecules, including intereactions with ultrashort laser pulses having possibly few optical cycles. Such processes are in general difficult to treat because electronic interactions with both laser fields and atomic and molecular potentials must in general be treated non-perturbatively, and in addition short pulse interactions must be described timedependently. Recent work has involved the solution of a weakly bound electron in a short-range potential interacting with an intense laser field essentially exactly and the results describe very accurately recent experiments for negative ion detachment in intense laser fields. This will be extended to treat in addition the presence of weak attosecond or few femtosecond pulses by means of time-dependent perturbation theory. Coulomb field effects for neutral atom targets will be incorporated by direct solution of the time-dependent Schrdinger equation for a laser pulse (or pulses) of arbitrary intensity. The effective range approach, which is largely analytic, permits a simple scan of the parameter space of laser frequency, intensity, polarization, pulse duration, and carrier envelope phase. The fully numerical direct solution of the time dependent Schrdinger equation will then focus on the most interesting regions of the parameter space for the case of neutral atoms, which are most commonly studied experimentally. Processes proposed for study include novel means of enhancing the intensities of high-order harmonic plateaus, which are currently essential for producing attosecond pulses; investigating the use of short, few cycle pulses to control rescattering of electron wave packets, which is crucial for production of plateau features in all strong field processes; and investigating the influence of Coulomb fields on above threshold ionization angular distributions by elliptically polarized laser light and on enhancing the intensities of plateau structures in strong field processes at multichannel thresholds.