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 and on investigating the use of ultrafast (attosecond scale) laser or electron pulses to pump or probe electronic processes in atoms and molecules. Such processes are difficult to treat theoretically because electronic interactions with both intense laser fields and with atomic and molecular potentials must in general be described non-perturbatively; also, interactions with short laser or electron pulses must be described time-dependently. In support of these investigations we have developed a number of new theoretical approaches. Investigations include using attosecond scale electron pulses as both temporal and spatial probes of electronic motion in both atoms and molecules; investigating the origin of laser-intensity-induced enhancements of ionized electron yields for electron energies corresponding to the so-called "ATI plateau"; developing novel closed form analytic formulas for high order harmonic generation amplitudes and rates for negative ions, extending those results to neutral atoms, and applying those results to seeking ways to enhance high order harmonic yields; and investigating two-electron effects in high order harmonic generation by short-pulse lasers. Graduate students and postdoctoral researchers involved with this project are given a broad education in theoretical atomic physics, first hand experience in all aspects of scientific communication, and in teaching undergraduates at a large AAU Land Grant university. Project results are not only published in leading physics journals and presented at national and international meetings, but are also periodically distilled and integrated with related work by others in review articles written by the PI and collaborators. All graduate students and postdoctoral researchers involved with this project in the past have been sought after by a variety of other employers, including technology companies, medical researchers, and other leading AMO theory groups. The basic research supported by this project contributes broadly to our understanding of means to control matter on an atomic scale. Our work on increasing the intensities of high order harmonics may one day lead to sources of coherent x-rays, thus providing a new means for visualizing living biological structures as well as nanoscale materials structures. Our investigations involving attosecond pulses of electrons may lead to ways of resolving electron motion both temporally and spatially. A workshop on attosecond science at the Kavli Institute for Theoretical Physics co-organized by the P.I. in 2006 has helped to enhance the infrastructure for research in this emerging new discipline. The P.I.'s co-editing of a special focus issue of New Journal of Physics on attosecond science in 2008 is evidence of his continuing service to the research community.