ELECTRONIC TRANSITIONS OF F-CENTER IN ALKALI HALIDES

Topological wave functions, in the form of localized free-electron orbitals, are used to describe the F center in alkali halides of the NaCl structure. Previous calculations on the F-band transition energies are extended to the K and L bands, confirming that these are higher-energy trnasitions of the F center. Oscillator strengths are calculated for the F and K bands. The model treats these bands as tangential excitations of the free-electron orbitals, and shows that the allowed radial transition correlates well with the β band. The low transition energy and long lifetime of F emission follows directly from the theory. © 1969 The American Physical Society.