Axial and planar channeling phenomena in quartz

Abstract

Axial channeling along the [00.1] c-axis and the [2λ.0] A ₂-axis of α-quartz as well as planar channeling along planes containing one of these two axes were studied. The effects of silicon and oxygen sublattices were separated by using backscattering for the silicon sublattice and the nuclear reactioq O¹⁶(d,p)O¹⁷∗ for the oxygen sublattice. Experiments were carried out with H⁺, D⁺ and He₄ ⁺ in the 0.5 MeV to 2 MeV range. Results represented using well chosen reduced coordinates follow single laws satisfactorily. For axial channeling the full width at half minimum l_1/2 of the surface extinction curves depends on √Z ₁ Z ₂/Ed. For the channeled fraction the reduced depth is xp ²dZ ₁/E,p ² corresponding, even for the silicon sublattice. to the thermal vibrations of the oxygen atoms. The results obtained for the minimum yields are in good agreement with those calculated. The depth dependence of l ^1/2 shown. A rather weak effect is observed for silicon planes (not larger than 50 per cent). For the oxygen planes, the effects are very small. Detailed calculations are carried out along the (01.1) plane for the silicon sublattice. An angle l _1/2 of 18′ is measured at the surface for 0.9 MeV deuterons. A diffusion model taking into account the multiple scattering by the oxygen atoms, considered as randomly distributed scattering centers, compares favourably with the experiments.