Infrared Spectra of KU1 and KS-4V Quartz Glass Irradiated by Fast Neutrons

Abstract

IR absorption spectra of quartz glass with varying contents of hydroxyl OH groups, namely, KU1 (1000 ppm OH) and KS-4V (≤0.1 ppm OH) are compared prior to and after exposure to fast neutron fluences of 10¹⁸–5 × 10¹⁹ cm^–2. The appearance of the IR absorption band of 2260 cm^–1 regardless of the large difference in the content of OH groups in nonirradiated KU1 and KS-4V glass is related to the bending vibrations of the bridging ≡Si−O−Si≡ bonds. A decrease in the amplitude of the band at 2260 cm^–1 and shift of its maximum by 20 cm^–1 to the IR range is caused by the decrease in the bridging ≡Si−O−Si≡ bond angle with the growth of the neutron fluence. The asymmetric band at 3674 cm^–1, which is related to OH groups, is observed only in nonirradiated KU1 glass. An increase in the number of OH groups in KU1 glass and the formation of OH groups in KS-4V glass after the accumulation of the neutron fluence of ≥10¹⁹ cm^–2 rationalizes the slow accumulation of the intrinsic defects such as nonbridging oxygen atoms and oxygen vacancies in both brands of the glass in the range of the neutron fluence.