Hot-carrier thermalization and trap level population dynamics in a $\mathrm{CdS}$ crystal on a femtosecond time scale

We present the results obtained in the experimental studies of a semiconductor $\mathrm{CdS}$ crystal using a femtosecond spectroscopy technique. The trap level was found to be populated via the two-photon interband excitation process, and its relaxation lifetime was about 550 ps. The duration of ultrashort stimulated recombination emission was directly measured and found to be less than 400 fs. The estimated carrier-phonon interaction time was of 20 fs order.