Applications of Stepwise Electron and Laser Excitation Of Atoms To Atomic Collision Studies
Over the past decade, the application of tunable dye lasers to the field of electron-atom collision physics has produced a range of new techniques for investigating collision processes. One of these techniques utilizes stepwise excitation of target atoms by a combination of electron and laser excitation. Information about the collision processes involved in the electron excitation step is obtained from intensity and polarization measurements made on fluorescence emitted from the stepwise excited atoms. Such experiments fall into two categories determined by whether laser excitation is used in the first or second excitation steps. In the former case, electron excitation from the laser excited state to higher lying states provides information on excited state collision parameters. In this paper, we consider only the latter case which provides new techniques for studying the electron impact excitation of ground state atoms (1–7) and allows several aspects of such collision processes to be studied in new detail. The narrow bandwidth of laser radiation permits the fine and hyperfine structure of many atomic transitions to be resolved in the laser excited step providing a method for studying the effects of such structure on atomic collisions, as in the case of tests of the Percival-Seaton hypothesis, or for eliminating such effects in the measurement of atomic collision parameters.
KeywordsLaser Excitation Electron Excitation Hyperfine Structure Density Matrix Element Quantisation Axis
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