Optical Absorption of Pure Silver Halides

The absorption spectra of pure silver bromide and silver chloride crystals grown from the melt have been measured in and near the so-called "absorption edge," where the absorption coefficient increases very rapidly with frequency. The temperature-dependence of the absorption edge has also been investigated. More limited data have been collected on the absorption spectra of mixed AgBr---AgCl and AgBr---AgI crystals.The requirements for an accurate measurement of the absorption edge in pure materials are discussed briefly, and it is estimated that the room-temperature data reported here are accurate to somewhat better than 10%. These new data are combined with some published measurements in an effort to obtain absolute absorption spectra for silver chloride and silver bromide over a large range of absorption coefficients.