  We performed mixed quantum-classical molecular dynamics simulations based on
first-principles potential-energy surfaces to demonstrate that the scattering
of a beam of singlet O2 molecules at Al(111) will enable an unambiguous
assessment of the role of spin-selection rules for the adsorption dynamics. At
thermal energies we predict a sticking probability that is substantially less
than unity, with the repelled molecules exhibiting characteristic kinetic,
vibrational and rotational signatures arising from the non-adiabatic spin
transition.
