The optical deformation-potential constant, otherwise inaccessible in undoped materials, is measured in CdSe by optical spectroscopy with subpicosecond time resolution. The phonon-assisted transitions from B to A excitons occur with a decay time of 0.9 ps, determined by pump-and-probe experiments. An analytic expression for the transition time is obtained. Since the Fröhlich interaction is symmetry forbidden, we use a nonpolar optical Hamiltonian and extract a deformation-potential constant of ${\mathit{d}}_0$=32 eV.

• Received 21 March 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.2335