INFLUENCE OF NEUTRON-IRRADIATION ON INFRARED-ABSORPTION IN GLASSY ARSENIC TRISULFIDE

The effect of irradiation in a cooled reactor channel on infrared abso rption in glassy arsenic trisulfide which contains water or is anhydro us, has been studied. Irradiation broadened the edge absorption in the direction of longer wavelengths and also changed the positions and in tensities of a number of absorption bands due to local vibrations of i mpurities. The observed changes in the spectrum are attributed to stru ctural modifications of the glass matrix, which increases the edge abs orption, and to the changes in the state of water contained by the mat erial, which leads to changes in the impurity absorption. The main pro cess that governs changes in the impurity absorption is the dissociati on of water molecules. A comparison with the infrared spectrum of glas sy As2S3 determined by us earlier after irradiation with Co-60 gamma r ays led us to the conclusion that the changes in the state of water ar e primarily associated with a high-power flux of the reactor gamma ray s. Nuclear reactions induced by thermal neutrons create selenium in th e As2S3 network and give rise to additional absorption due to the vale nce vibrations of the Se-H an S-H bonds (the source of hydrogen clearl y is the process of dissociation of water contained in the original sa mples). The impurity absorption of the anhydrous material is not affec ted by irradiation, which confirms this conclusion. Structural changes in the glass matrix are mainly due to the action of fast neutrons.