Attenuated total reflectivity of semiconductors with wave-vector-linear band splitting

We have calculated the attenuated total reflectivity (ATR) of a semiconductor near an excitonic transition in the presence of wave-vector-linear energy-band splitting. The numerical work corresponds to the B(n=1) exciton of CdS, the light being p(TM) polarized in a plane perpendicular to the crystal axis. The ATR spectra reveal two minima: One is a broad minimum between T and L (the transverse and longitudinal exciton frequencies) and the other is a narrow minimum at T. These resonances are interpreted as corresponding, respectively, to the ordinary (essentially local) surface-exciton-polariton and to a new (nonlocal) surface mode.