An optical sector of electron-atom resonances: its possible detection and relevance for resonant-process studies

The analysis of a theoretical equation for the double differential cross-section of electron-atom collisions, in which <> (BS) photons are produced, and in particular of its dependence on both photon energy and electron scattering angle, shows that there is an optical sector of electron-atom resonances, that is, the appearance of resonance dips in BS cross-section. When considering, for instance, the resonance that the rare gases exhibit at nearly 0.5 eV below excitation threshold, this optical sector, or in other words the BS photon energy distribution, presents one or two resonancelike structures whose positions depend on both electron energy and scattering angle. By suitably choosing these parameters, one of these optical-resonance images can be made to occur at easily detectable photon energies. A successful experiment could be performed by utilizing an electron-photon coincidence method such as those used for studying coherence and correlation in electron-atom collisions. Particular conditions for such an experiment are considered, and its possible relevance for better insight into electron-atom resonances is outlined. (orig.)