Real-Time Observation of a Metastable State during the Phase Transition in Shocked Cadmium Sulfide

A method was developed to perform ps time-resolved electronic spectroscopy in shock wave experiments, and used to examine the initial stages of the phase transition in CdS. Changes in the electronic spectra were observed with 100 ps resolution in single crystals shocked to stresses between 3.6--8.8 GPa. The absorption results suggest that the initial stage of the transition is characterized by a very rapid transformation to an indirect band gap material. Along with earlier ns continuum data, these results make a strong case for a metastable state during the phase transition in shocked CdS.