27Al(p, γ)28Si Narrow Resonance in Channelling: a Measurement of Inelastic Energy Transfers at Small Impact Parameters

We have studied the excitation curve of the 27Al(p, γ)28Si narrow resonance (ΓR = 105 eV) at 992 keV in random and axial channelling geometry on a clean (110) Al single crystal under UHV conditions. The results are compared to semi-analytical calculations and to Monte Carlo simulations. The comparison for the aligned case provides the impact parameter dependence of the mean inelastic energy transfer. At low impact parameter (~ 0.15 A) with respect to the strings, these transfers are ~ 8 times higher than in random conditions. The mean energy transfer to inner-shell Al electrons is shown to be proportional to the corresponding electronic density sampled by the ions, in good agreement with theoretical impact parameter treatments of the energy loss.