Out of scattering plane (e,2e) and laser assisted electron impact autonionization studies of helium

Grants and Contracts Details


Two experiments on He ionization are proposed that build on the s~vrk done during the present grant period. The first, motivated by major disagreements between theory and experiment reported in the literature, will measure out-of-scattering-plane (e,2e) angular distributions at a range of incident electron energies, for a full 3600, using a special geometry that allows out-of- plane conditions to be combined with the binary peak in a single measurement. Data will be taken in the energy region of He autoionizing states, both on and off resonance. The results will be compared to state-of-the-art first and second order calculations. Of particular interest are the experiments at low incident energy where the out-of-plane region is expected to have enhanced intensity. This experiment will use an (e,2e) apparatus modified during the present grant period to allow the electron gun to move on the surface of a (mathematical) cone. We will continue our successful collaboration on this experiment with Klaus Bartschat's theory group at Drake University, Iowa. The second experiment will investigate electron-impact helium autoionization in the presence of a laser field. Preliminary experiments carried out during the present grant period have seen an enhancement of the autoionization peaks when the laser beam is present. These experiments will be continued to confirm this result. Ejected electron spectra will be measured at a range of angles with respect to the laser polarization. In addition to measuring changes in autoionization intensity and lineshape due to the laser field, we will look for "sidebands" separated from the normal autoionization peaks by energies equal to integral numbers of the photon energy. The advantage of this type of experiment is that it isolates the photon-target interaction from the photon-projectile interaction; there is at present poor agreement between experiments that involve both types of interaction and theories that emphasize the photon-projectile interaction. These experiments use one of the P1's apparatuses that has been extensively modified during the present grant period and has been interfaced with one of the Co-PT's Nd:YAG lasers. limui4erim acts resulting from the Proposed Research The research will involve both undergraduate and graduate students at the University of Kentucky. Undergraduates will work on a project such as data analysis. The project will provide dissertation material for at least two graduate students. Students acquire skills in lasers, electronics, vacuum systems, and computer programming, networking, and interfacing with experiments. They present their work at national and international con- ferences.
Effective start/end date8/1/097/31/15


  • National Science Foundation: $340,000.00


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