RUI: Investigations of One- and Two-Color Laser-Assisted Electron Scattering

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Knowing the microscopic structures of molecules and materials is key to understanding their physical and chemical properties and therefore their basic functions and technological applications. However, in addition to measuring structures, which is widely carried out using electron scattering, physicists seek to understand the interactions that occur between electrons and molecules during the scattering process itself. This knowledge can then be used to develop more sensitive techniques for determining structures, for example, while a molecule is undergoing a structural change. Knowledge gained through these studies can also influence applications of electron-atom-laser interactions, which include the generation of short pulses of extreme ultraviolet light that are used to measure ultrafast physical and chemical processes. The goal of this research is to understand electron-atom scattering in the presence of an intense laser field, in particular, how electrons in atoms and molecules respond to intense fields. Without the laser field, the simplest thing that can happen is that the electron and the atom do not exchange energy and continue on their way after the collision with the same energies that they had before the collision, possibly changing only their direction. Addition of light from a laser can cause such ?elastically? scattered electrons to absorb some number of photons, which increases the energy of the electron, or emit photons, thereby reducing the electron's energy. These are called laser-assisted free-free (LAFF) processes because the electron is free, i.e., not bound to an atom or molecule, both before and after the collision. This work will involve experimental LAFF studies, with the broad aim of increasing our basic understanding of these processes. Particular attention will be paid at looking for interference effects in LAFF experiments that use a two-color (photon energy = 1.17 eV, and 2.34 eV) laser field, and which might be used to control scattering processes. In addition to the advancement of our basic understanding of scattering processes, this work has applications to a variety of fields, both basic and applied. For example, LAFF processes are important for understanding the interiors and atmospheres of stars. Free-free transitions also play a major role in the gas breakdown that occurs in electric discharges, and provide a method for laser heating of a plasma (a gas of ionized atoms). This work will primarily take place at an undergraduate institution, and will directly involve several undergraduate students in research.