Optical properties of arsenic trisulphide

Abstract
The optical absorption spectra ( E || c , E ⊥ c ) of As 2 S 3 have been determined from transmission measurements on single crystals ranging in thickness from 550 to 0·07 μm, At 77 °K the absorption spectrum ( E || c ) consists of three absorption bands A, B and C at 23300, 24100 and 25600 cm -1 respectively. The absorption bands for E ⊥ c occur 500 cm -1 to the high energy side of those for E || c . The variation of absorption coefficient α with photon energy hv at the absorption edge (290°K) can be resolved into four regions each of which is described by the equation α = a ( hv + b ) 2 . At 290 and 77°K the single crystal reflexion spectra ( E || c , E ⊥ c ) show maxima associated with the absorption bands and an additional maximum at 35000 cm -1 . The calculated and measured reflectivities are in good agreement. Measurements have been made of the dispersion of the principal refractive indices and of the optic axial angle. The spectral distribution of photocurrent shows peaks associated with absorption bands B and C ( E || c , E ⊥ c ).

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