SPIN-ORBIT-COUPLING, SPIN-LATTICE RELAXATION, AND SPIN-MEMORY STUDIESOF F-CENTER-MOLECULAR-ION PAIRS IN ALKALI-HALIDES

The spin-orbit parameter DELTA, spin-lattice relaxation time T1, and s pin-mixing parameter epsilon of F(H) (OH-) and F(H) (CN-) centers in s everal alkali halides have been studied with magnetic circular dichroi sm at approximately 2 K. A close comparison of the experimental result s before and after optically induced association of the F center with the molecular ion has been made. In crystals of NaCl structure the neg ative spin-orbit parameter DELTA changes little between F and F(H) cen ters in the same host. For CsCl and CsBr two values of DELTA have been derived for F(H) (CN-) centers with axis parallel or perpendicular to the magnetic field. In all studied systems, the spin-lattice relaxati on time T1 is already shorter before aggregation compared to F centers in pure crystals, and becomes further shortened by the F(H)-center fo rmation. The spin-mixing parameter epsilon decreases slightly for F(H) (OH-) compared to F centers, while it increases drastically for F(H)(C N-) defects and reaches its maximum possible value epsilon = 0.5 in ce sium halides. First attempts to interpret these magneto-optical result s will be presented.