State-to-state rotationally inelastic scattering of ND3 on a graphite (0001) surface

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Abstract
State‐selected molecular beams of deuterated ammonia, ‖JKMε≳‖inversion≳=‖1111≳‖−≳ or ‖222−1≳‖−≳ and ‖3331≳‖−≳ states in the proportion 2.3:1, are produced via hexapole electrostatic focusing and then scattered at near‐normal incidence on a graphite (0001) surface at Ts=130 K. The post‐collisional rotational distribution of directly scattered molecules is monitored by laser photoionization spectroscopy. It is observed that the state‐to‐state rotational transitions in the surface scattering of ND3 are strongly coupled to the inversion symmetry change, as predicted by Corey and Alexander [J. Chem. Phys. 89, 790 (1988)]. This coupling may be viewed as a constructive and destructive interference between the ‘‘left’’ and ‘‘right’’ inversion configurations of the molecule on the surface potential. The selection rules prohibiting para to ortho conversion, which have been predicted by Corey and Alexander for rotationally inelastic scattering of ammonia, are observed to be violated, perhaps, due to ND3 distortion at the impact.