Electron capture by slow multiply charged ions colliding on rare-gas targets is known to populate highly excited states of the projecile with very large cross sections. For double electron capture, (n, n') series with n = n' are, in general, preferentially populated. Though theseslates arcalmost camplctelyautoioniilng, important radiative decay following double capture has been reported. Recently the fluorescence from n<< n' Rydberg states has been observed. These findings are important since they strongly modify the charge and radiation balance of the multiple charge exchange reactions. We propose here a mechanism based on post-collisional effects which feeds Rydberg states from the quasi-symmetrical doubly excited states initially populated. A simple quantitative estimate of this effect is proposed on the basis of the well known 'Barker and Berry' formula.

It is shown that inner displacement has a large effect on the collective coordinates of the Tz modes in strained crystals of the zincblende structure. This has important implications for the interpretation of stress-dependent phenomena in gallium arsenide and similar materials.

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