EXCITONS IN BEO

BeO crystals in both orientations (perpendicular-to c and parallel-to c) are studied under polarized synchrotron radiation. The long-wave shift (43 meV) and the splitting (29 meV) of the main excitonic reflection peak in the case of E parallel-to c are detected at 10 K. The correspondence of the observed transitions to the selection rules is discussed. The excitation spectra of the luminescence band of self-trapped excitons are measured in the excitonic region. It is found that in the case of E parallel-to c the excitation spectrum is characteristic of localized excitations. Possible evidence of the coexistence of large- and small-radius (self-trapped) exciton states is discussed.