Simultaneous off-shell excitation of He 23
S by an electron and one or more photons |
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Authors: | B Wallbank J K Holmes L Le Blanc A Weingartshofer |
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Institution: | 1. Department of Physics, St. Francis Xavier University, B2G1C0, Antigonish, Nova Scotia, Canada
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Abstract: | We report data on the excitation of the 23 S metastable state in helium by electrons in the presence of an intense laser field. The metastable signal is detected when the electron energy is insufficient to excite this state by itself. The additional energy comes from a pulsed CO2 laser developing peak intensities in the interaction region in the 108 W× cm?2 range and requires the absorption of one or more photons. This process involves the active participation of all three bodies: the electron, the photon and the target atom. These data represent the first observation of this process when more than one photon is required. |
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