Electron photon coincidence measurements on the inert gases

A coincidence technique was used to measure the angular correlations between electrons which have excited the first excited states of the inert gases and the photons which arise from the decay of these states to the ground state. This technique yields measurements of the differential cross section for the excitation of the degenerate magnetic sublevels and also the relative phases of the corresponding excitation amplitudes. Such measurements constituted an even more sensitive test of scattering theory than even the observation of the polarization of resonance radiation because this involves integration over the contributions from the various sub states. The coincidence technique is described and its application to the targets helium, neon and argon will be discussed. The data will be compared with that predicted by the Born and Glauber approximations. It is shown that both these approximations give poor descriptions of the angular correlations. Preliminary data are presented on the use of a coincidence technique to observe resonant states in electron atom interactions. (author)