Calibration of infrared spectroscopy by elastic recoil detection analysis of H in synthetic olivine
Résumé
Elastic recoil detection analysis (ERDA)was used tomeasure the H contents of 18 synthetic Fo90 olivines that had been hydrated to varying degrees in high pressure hydrothermal experiments. The infrared spectra of the olivines have been previously measured in the OH stretching region by Fourier transform infrared spectroscopy, and 16O1H secondary ion mass spectroscopy measurements have been made on the same samples. Mapping by ERDA, Rutherford backscattering and particle induced X-ray emission spectroscopies show that the synthetic olivines are homogeneous with respect to major element and H concentrations. Concentrations of H measured by ERDA vary between 270 and 2120 ppm H2O. Measurements of OH/Si ratios by secondary ion mass spectroscopy and of total integrated area of OH stretching bands in principal absorption spectra by FTIR show excellent linear relationships to H concentrations determined by ERDA. The ERDA measurements are used to determine an infrared integral molar absorption coefficient of 45,200 l mol−1 cm−2 that can be used to determine H contents of olivines from high pressure experiments. The H content of Fo90 olivines (in wt. ppm H2O) is given by 0.119±0.006×total integrated absorbance per cm thickness.