Ion beam analysis and microscopic characterization of natural topaz stones

Abstract

Rutherford backscattering spectroscopy (RBS) and elastic recoil detection (ERD) techniques were used to determine the presence of metallic as well as nonmetallic (also hydrogen) components in two kinds of natural topaz stones originating from Sri Lanka and Nigeria. A computer simulation program was applied in order to compare the theoretical and experimental results of the RBS analysis. The changes in surface morphology induced by irradiation with high energy analysing ion beams were monitored using optical microscopy. RBS analysis proved the presence of trace amount of metallic admixtures in the stones — potassium, zinc, nickel or cobalt, lead (and/or bismuth) were detected mainly in the surface region of the samples. ERD analysis allowed to determine the total content and depth distribution of hydrogen; the depth distribution of hydrogen was proved to be almost uniform. Microscopic investigation indicated the existance of damage and precipitates on the polished surfaces, whereas radiation damage, probably connected with helium-blistering, was observed after the ERD analysis.