Collisions of NO(X 2II) with a Ag(111) surface: Validity of the energy sudden approximation

Abstract

Energy sudden calculations of the rotationally inelastic scattering of ground-state (NO(X 2 II) from an uncorrugated, rigid Ag(111) surface have been carried out. In this approximation, the inelastic transition probabilities are obtained by solution of a fixed-orientation, single-channel Schrodinger equation, which must be solved for each of the two adiabatic potential energy surfaces which arise when a molecule in a 2 II electronic state interacts with a surface. These two potential surfaces were based on a description of the NO−Ag(111) potential used by Muhlhausen, Williams and Tully [J. Chem. Phys. 83 (1985) 2594]. Comparison of the calculated transition probabilities with the results of our previous close-coupling calculations at a collision energy of 6700 cm −1 shows that for this potential, which possesses a deep, strongly anisotropic, and fairly long-ranged attractive region, the sudden approximation predicts significant flux into high rotational levels which are neither energetically nor dynamically accessible. The dependence of the collisional transition probabilities on the symmetry of the electronic wavefunction of the NO A -doublet state, with respect to reflection in the plane of rotation of the molecule, is described reasonably well within the sudden approximation. The sudden results also adequately predict the relative flux into rotational levels associated with the two ( Ω =1/2 and Ω =3/2) spin-orbit manifolds of NO.