<title>Exciton luminescence in beta-ZnP2: 2s and 3s</title>

Abstract

ABSTRACT Secondary emission spectra in the higher region of exciton band of ZnP2 single crystal are measured at 6K with a tun- able Ti:sapphire laser as an exciting light source. The luminescence bands due to the radiative recombination of the 2s, 3s and 4s excitons are clearly observed separately. It is also found that the 1LO Raman line with energy of 32.2 meVshows resonance enhancement near the 2s exciton band. On the contrary, the intensity of the 1LO Raman line becomes anomalously weak when it is just superimposed on the 3s luminescence peak. The shapes of these luminescence bandschange considerably when the 1LO Raman line approaches them. The changes in intensity of the Zr and 3s exciton bandswith the excitation energy are briefly discussed in regard to the relaxation processes of polariton.1. INTRODUCTIONMany aspects of the exciton polariton such as lumines— cence, reflectivity and nonlinear optics have been exten—sively studied in a large number of semiconductors (e. g., CdS, ZnTe and CuCl). For many years the center of inter—ests has been directed to the resonance region of the is exci—