Double optical resonance spectroscopy of the Nd3+ ion pairs in LaF3 crystal

We present the results of absorption spectra measurements of Nd3+ ions in the LaF3 crystal in the vicinity of the I9/24(1)-G5/24(1) 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.