Vector classification, doublet splitting of exciton and biexciton subbands in crystals, and selection rules for transitions between them

Abstract

The analysis of experimental data on absorption, reflection, luminescence in the region of exciton and biexciton phototransitions in CdS, including P-band structure, shows that there is doubled, contrary to known theory, number of free exciton and biexciton states. This discreapancy is removed in the vector model of these states presented in this paper. The selection rules for transitions between exciton (biexciton) states in crystals taking into consideration their L-T splitting are obtained. The spectra of stimulated FIR radiation on excitonic transitions in CdS, previously obtained experimentally, well fit to these selection rules.