Electronic spectra and electronic structure of the Cu+ ion in alkali halides

Abstract

The Cu+ ion as a substitutional impurity in alkali halide crystals provides a simple model system to learn in detail about the optical properties of ions in crystals. The absorption and emission spectra of the d10 ions Cu+ and Ag+ in many alkali halides have been previously reported. However, the recent application of high resolution one- and two-photon laser spectroscopy to these systems has revealed a wealth of new information. This article reviews these results with particular attention to the NaF : Cu+ system. This system is unique in that sharp vibronic progressions are observed in six of the eight excited electronic states and in the ground state. These data have led to the construction of potential curves for these states. Furthermore, polarized two-photon spectroscopy has been used to assign the absorption bands unambiguously. Other techniques such as magnetic perturbations, line-width studies, and uniaxial stress have also been used to further understand this system. Several theorists have carried out large-scale ab initio calculations; their results are compared and reviewed here. © 1991.