TIME-RESOLVED ABSORPTION CHANGES OF THIN CS2 SAMPLES UNDER SHOCK COMPRESSION - ELECTRONIC AND CHEMICAL IMPLICATIONS

Electronic and chemical changes in CS2 shocked to 12 GPa have been examined by using time-resolved absorption measurements. Experiments were carried out on thin samples (≈1 μm) to provide good resolution of the absorption spectrum between 280 and 500 nm in pure CS2 and to separate pressure, temperature, and time effects. In addition to the V-band existing at ambient conditions, a new band is observed on the red side of the V-band at high pressures. Unlike the V-band, the peak position and intensity of the new band vary substantially with pressure and temperature. The new band shows a "hot" band character and is conjectured to be the T-band resulting from a transition to the 1A2 state. The edge shifts of the absorption band, at a given pressure, decrease with decreasing temperature. The time-dependent increase in absorbance and the magnitude of the edge shifts cannot be reconciled with temperature changes and are believed to represent changes in the electronic structure due to diffusive molecular motions. Spectral changes are irreversible above 11-12 GPa due to a shock-induced chemical reaction. The absorption changes from this and previous work suggest that an associative type of chemical reaction occurs in shocked CS2. © 1990 American Chemical Society.