CLOSE-COUPLED WAVE-PACKET CALCULATIONS OF THE DIRECT INELASTIC-SCATTERING OF NO(X2II) FROM AG(111)

In this article we report an application of the time-dependent close-coupled wave-packet (CCWP) method to the rotationally inelastic scattering of NO(X 2Π) molecules from a rigid, flat Ag (111) surface. Previous applications of the CCWP method have been restricted to either direct scattering off purely repulsive potentials requiring short propagation times, or weakly physisorbed systems in which only a few internal states are coupled. The calculations reported here were performed for a molecule in an initial state with a momentum distribution peaked around E = 6700 cm-1 scattering off a strongly anisotropic potential with a well depth of 4400 cm-1 and a long-range tail. Numerical procedures were introduced which enhance the efficiency of the CCWP method whenever a large number of internal states or a large number of grid points are needed to simulate the collision. For the current application to NO-Ag these techniques reduced the required CPU time by more than an order of magnitude. The resulting state-to-state transition probabilities are compared with previous time-independent close-coupled calculations, and with the semiclassical self-consistent eikonal method (SCEM). The agreement between the two quantum-mechanical methods is well within the accuracy of both numerical procedures. A comparison of the instantaneous transition probabilities calculated throughout the propagation shows good agreement between the CCWP and the SCEM calculations at high collision energies. © 1990 American Institute of Physics.