Surface Exciton Polariton in CuCl and CuBr

The surface-exciton-polaritons arc investigated by the attenuated-total-reflection (ATR) method on the evaporated films of CuCl and CuBr. Double dips observed in the ATR spectra of CuCl are attributed to the Z 3 and Z 1,2 excitons. In CuBr, the dip is detected only for the Z 1,2 exciton. The characteristic features of the ATR spectra are well accounted for by the local dielectric functions for the excitons. An effect of the finite exciton mass on the ATR spectra of CuBr is discussed.