Electron-Atom Scattering Dynamics

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In 1914, J. Franck and G. Hertz performed an experiment which played a vital role in establishing modern atomic theory.  That experiment, for which they won the Nobel Prize in 1925, examined the collisions of electrons with mercury atoms.  The field of electron-atom (molecule) scattering has grown enormously, both in sophistication and importance, since that first study.  The growing importance of this field arises from the discovery of numerous and diverse natural phenomena, as well as technological processes, which involve electron-atom (molecule) collisions.  The immense spectrum of relevant phenomena includes processes occurring in the upper atmospheres of the planets, processes occurring in fusion plasmas, techniques applied to the fabrication of semiconductor devices and occurrence of radiation damage in living tissue.  Complete understanding of these phenomena and the further development of the relevant technological processes requires the quantitative characterization of electron scattering from the atoms (molecules) of interest and supplies the motivation for the continued study of this field in the laboratory.   In this grant application, funding is being requested to support an ongoing program in the experimental investigation of electron collisions with atoms and molecules.  Our primary interest is currently focused on collision phenomena involving excited-state atomic targets, a field which remains largely undeveloped but is of great practical value in plasma studies.  Our method involves pre-excitation of the atomic target by laser radiation and the measurement of collision processes involving this pre-excited target.  Such techniques are developing rapidly as important tools in collision studies where lasers can be utilized as a means to control and probe collision reactions.  In our case, in addition to providing an efficient mechanism for the production of high concentrations of excited scattering targets, the use of laser radiation allows us to prepare the excited atom in a "pure quantum state".  We can thereby elucidate the physics of the collision process and make the connection with new theoretical models at the most fundamental level possible.