Nuclear Reaction Analysis of Corroded Glass Surfaces

Abstract

The nuclear reaction analysis (NRA) method based on the ¹⁵N + ¹H → ¹²C + ⁴He + γ-ray nuclear reaction is used to profile the concentration of hydrogen as a function of depth in glass samples. This approach is useful in several fields of study including glass corrosion and dating of obsidians for archaeological purposes. However the application of the NRA technique to corroded glasses requires some special considerations. In particular, because glasses are insulators, a system is needed to suppress the build-up of charge on the samples during analysis. Further, the hydrogen in some types of corroded glasses is loosely bound and care must be taken to minimise hydrogen losses during profiling. This can be accomplished in most cases by freezing the samples prior to evacuation and analysis, and by rastering the ion beam over a large area, keeping the total amount of accumulated charge on the sample to a minimum. The presence of glass corrosion products on the glass surfaces is also discussed.