Type I FA and Type II FA Tunable Laser activity and Interaction of Halogen Atoms (F,Cl, Br, I, At) at the (001) Surface of KBr Crystal: ab Initio Calculations

The effects of type I FA and type II FA color centers on tunable laser activity and adsorbate–substrate interactions of halogen atoms (F, Cl, Br, I, At) at the (0 0 1) surface of KBr, are investigated by using quantum mechanical CI singles and DFT ab initio methods. Clusters of variable sizes were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surface, and ions that were the nearest neighbors to the defect site were allowed to relax to equilibrium in order to calculate the optical properties. The sensitivity of the calculated transition energies (Stokes shifts) of Type I FA and Type II FA laser as well as related optical properties such as relaxed excited states orientational bleaching, defect formation energies, exciton (energy) transfer, and the Glasner –Tompkins empirical rule, to the coordination number of the surface ion were examined. The effects of F and FA center on the halogen atom surface interaction as well as the relative roles of energy gaps and spin pairing in the course of adsorbate–substrate interactions were examined.