A new type of coincidence experiment for the study of inner atomic shells

A new type of coincidence experiment is proposed for the study of ionisation of inner atomic shells by electron or proton impact, namely, experiments where a 'slow' ejected electron and an Auger electron (or an x-ray photon), arising from decay of the ion formed, are detected in coincidence. A theoretical treatment is given of the anisotropy of the ionic state and of the anisotropy and polarisation of following radiation. Convenient formulae for the analysis of real experiments, as well as approximate expressions for the angular correlation functions suitable for estimates, have been obtained. The numerical calculations made for the ionisation of the 2psub(3/2) subshell of Ar and the 3dsub(3/2) subshell of Kr have confirmed the possibility of setting up such experiments and the high sensitivity of the investigated correlation functions to the ionisation mechanism and atomic models. The effect of the interaction in the final electron-ion state on the correlation characteristics of interest here is examined. (author)