Optical properties of U centers in alkali halides and alkaline earth fluorides

Abstract

The two-electron orbitals for the U ce nte r have been co mputed numeri call y from the HartreeFock-Slate r (HFS) equation s in th e point-ion lattice potential. The latti ce relaxation of the neares tneighbor io ns is included in the model. The fiv e low es t-lying U-center st~tes for NaCI, K CI, CdF2, CaF2, SrF2, and BaF2 are given. The low -l yin g sin glet states have the followlll g order for IIl creaslll g values of the energy : I S (Is, Is), I P (Is , 2p), and I S (Is, 2p). The ene rgy leve ls for the triplet states 3 S (Is.' 2s), and 3 P ( Is. 2p) lie bet ween th e energy levels for th e IS (Is , Is ) and I P (Is , 2p) states. The ord enng of the triplet states depends upon th e hos t crystal and th e latti ce relaxation. The predi ctions based upon the num erical HFS wave fun ctions are compared with th e predi ctions based upon past variational wave fun ction s and with ex perim e nt.