Picosecond energy-relaxation processes of excitons in CdSe

Energy- and time-resolved luminescence of the one longitudinal optical-phonon Stokes sideband of the $A$ exciton in CdSe has been studied in the picosecond time domain under the weak band-to-band excitation. Dynamic energy relaxation of excitons is directly visualized in the energy-time coordinates. The observed energy-relaxation rate of excitons is explained by a model taking into account three types of excitonphonon interactions, that is, the deformation-potential-type, the piezoelectric-type, and the Fröhlich-type interaction. This result clearly demonstrates the applicability of the method used in this work to the analysis of the energy relaxation of excitons.