Consideration of Polarization and Covalency Corrections to the Quasi‐Coulomb Shift of Optical Lines of Ion Pairs in Crystals

The effect of polarization and covalency corrections on the Coulomb interaction of impurity ion pairs in ionic crystals is taken into account. A simple semi‐empirical theory is suggested for the explanation of the quasi‐Coulomb shifts of the optical lines belonging to the pairs of equivalent impurity ions (in relation to the corresponding lines of single impurity ions). In this theory we use effective charges and effective electric dipole moments of ions. The theory is applied to the explanation of the optical spectrum of Cr3+Cr3+ pairs in ruby. The problem of a microscopical calculation of effective parameters is discussed.