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Energy spectra for 3 keV He+ scattered over 145° by an exchanged SiO2 sample (18O concentrations of 97% and 3%) using an Ep of 1 keV.
Scattered ion yields for 16O and 18O isotopes in SiO2 samples with 100% isotopic enrichment at different Ei. Closed symbols correspond to an Ep of 3 keV, open symbols correspond to an Ep of 1 keV.
Natural logarithm of the LEIS signal (peak areas) corrected for the differential cross-sections (σ) versus the sum of the reciprocal velocities before and after scattering for He+ scattered by SiO2. The yields were extrapolated to 100% O isotopic composition in the different samples. (a) 16O in 100%-enriched Si16O2, (b) 18O in 100%-enriched Si18O2, and (c) Si in both SiO2 samples. Circles: Ep 3 keV; squares: Ep 1 keV.
Ion fractions for Si, 16O and 18O in 100%-enriched SiO2. Dashed lines: AN mechanism; solid lines: CIN mechanism.
Characteristic velocities (Vc) and intercepts (a) as estimated from the linear fittings of the corrected scattering yields versus the sum of the reciprocal velocities of the He+ ions scattered by SiO2, extrapolated for 100% O isotopic composition. The straight lines for AN in O isotopes was defined by the intercept value (a) and the corrected scattering yield at Ei = 600–800 eV, assuming that CIN contribution at these E can be neglected.
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