Probing the molecule–surface interaction via inversion symmetry changes in the scattering of state-selected ND3 on graphite (0001)

By employing rotationally state-selected ND3 molecular beams, ‖JKMε≳‖inversion≳ =‖1111≳‖−≳, and REMPI detection, it is found that there is a propensity for inversion symmetry change from antisymmetric to symmetric states, ‖−≳ to ‖+≳, as compared to antisymmetric to antisymmetric states, ‖−≳ to ‖−≳, in the scattering of ND3 on a graphite (0001) surface at 130 K. The total probability of inversion symmetry change summed over the post-collisional rotational states is measured as a function of translational energy. We demonstrate that the observed effect is due to molecular self-diffraction on the surface and that it may serve as a new way to probe the molecule–surface interaction. Relying on the infinite order sudden approximation [Gerber et al., J. Chem. Phys. 73, 4397 (1980)], we suggest a procedure for inverting an approximate, corrugation-averaged molecule–surface interaction potential from experimental data on molecular self-diffraction; measurements of the probability of inversion symmetry change for different incident rotational states as a function of translational energy are required. Since we do not possess sufficient experimental data for a full-fledged analysis, computer simulations of the observed energy dependence are carried out with model interaction potentials.