Optical absorption measurements on silver halides in the ultraviolet and extreme ultraviolet energy ranges

Abstract

The absorption coefficients of silver chloride and silver bromide have been determined from thin film transmission measurements in the range of photon energy from 3.5 to 6.7 electron volts and from 30 to 240 electron volts. An unusual feature of this work is the use of electron synchrotron radiation for measurements in the high energy range. Optical constants have been calculated over the extended energy range, 3.5 to 240 electron volts. Band gaps have been estimated from the ultraviolet energy data and exciton binding energies. Comparison of ultraviolet structure and extreme ultraviolet structure, and measurements taken at different temperatures give evidence that in the high energy region exciton absorption is insignificant compared to absorption due to band-to-band transitions. A discussion of the conduction band structure of silver chloride is also given.