A STUDY OF THE FH(CN-) CENTER IN KCL AND CSCL - THE POTENTIAL-ENERGY SURFACE AND EV ENERGY-TRANSFER

Adiabatic potential energy surfaces (APESS) of the F(H)(CN-) centre in KCl and CsCl are calculated for the excited and ground states. It is shown that in CSCl the APES of the excited state intersects that of th e ground state on the path of de-excitation leading to the quenching o f emission. In KCl, the opposite situation is obtained in agreement wi th experiment. The calculation for CsCl shows a rapid variation of the dipole moment of the CN- molecule near the crossing region. The elect ronic-to-vibrational energy transfer (EV transfer) between the F centr e and CN- molecule is discussed in terms of the non-radiative transiti ons between the two intersecting APESs. The dipole-dipole coupling bet ween the F centre and CN- molecule (Dexter-Forster theory) is also con sidered to analyse certain aspects of the EV transfer.