Double optical resonance spectroscopy of the image ion pairs in image crystal

We present the results of absorption spectra measurements of image ions in the image crystal in the vicinity of the image transition. We show that satellites accompanying the line of an isolated ion are caused by ion exchange interaction. The structure of these satellite lines, hidden by the inhomogeneous broadening is revealed by means of the double optical resonance technique. Various ion interaction mechanisms which may be responsible for the observed structure are discussed.