Electron Spin Resonance Studies of Irradiated Glasses Containing Boron

Abstract

Electron spin resonance (ESR) spectra have been observed for various types of alkali borate and borosilicate glasses which were exposed to γ-ray or thermal neutron irradiations. The irradiated alkali borate glasses (Li2O–B2O3, Na2O–B2O3, K2O–B2O3, Rb2O–B2O3, and Cs2O–B2O3) containing less than 25 mole % alkali oxide exhibit spectra consisting of five peaks in the resonance absorption curve at an operating microwave frequency in the vicinity of 9.2 kMc/sec. The same five-line resonance has also been observed in the irradiated borosilicate glasses (Corning 7070, 7740, and 7720). Investigations of the irradiated glasses by means of a K-band ESR spectrometer operating at approximately 23.3 kMc/sec have yielded spectra which are partially resolved into six lines. Alkali borate glasses isotopically enriched with B10 display a 10-line resonance at the X-band frequency when irradiated with γ rays or neutrons. It is concluded that the five- and six-line resonances arise from an axially symmetric hyperfine interaction of a hole with a B11 nucleus, while the 10-line structure arises from such a hyperfine interaction with a B10 nucleus. The atom containing this B11 or B10 nucleus is believed to be in a BO4 tetrahedral configuration in the glass structure.