Predictions on the effect of initial molecular orientation and rotation on penetration of the (0 0 0 1) face of hexagonal ice by HCl

Molecular dynamics calculations have been performed for the penetration of the basal plane (0 0 0 1) face of ice Ih by HCl, at a surface temperature of 150 K and for normal incidence energies, Ei=1.0–2.0 eV. For initially rotationless (j=0) HCl, we predict a strong dependence of the penetration on the initial orientation of HCl, penetration being 60% more likely for ‘Cl-down’ HCl than for ‘H-down’ HCl at Ei=2.0 eV. Though in general, the penetration probability is independent of the molecule’s initial angular momentum j, penetration beyond the second bilayer (deep penetration) is suppressed by initial rotation. This suggests that the steering operative in deep penetration is inhibited by initial rotation.