Shift of optical absorption edge of amorphous As2S3 with increasing hydrostatic pressures up to 66 kbar has been quantitatively measured by means of high-pressure mic-rospectroscopic system in conjunction with gasketed diamond anvil cell under room-temperature. The method of ruby fluorescence shift technique was adopted for pressure calibration. Amorphous As2S3 thin film samples a few micrometers in thickness were prepared by vacuum evaporation. Under our experimental conditions, neither the light of 4416? He-Cd laser used for excitation of the ruby gauge, nor that of the Br-W lamp for measurement of light transmission, showed any detactable influence on the optical properties of the sample. Rapid red-shift of optical absorption edge with increasing pressure was observed, Eg dropped from 2.58 eV to 1.95 eV between 1 bar and 66 kbar. An empirical formula of experimental data was obtained. The relationship of absorption edge and pressure is as follows: Eg(P)=Eg(0)-1.31×10-3P-3.91×10-4P2+4.04×10-6P3. It is noteworthy that the dependence of |dEg/dP| upon pressure was increasing at first and then decreasing gradually to saturation at high pressure. This result shows something different from privious one obtained by Weinstein et al. The origin of the difference was discussed.
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