Scattering of NO molecules from a diamond (110) surface

Abstract

The translational, rotational, and vibrational dependencies of NO molecules scattered from a diamond (110) surface have been investigated for a series of scattering geometries. The integral and state selected angular distributions of the scattered molecules have been measured. In the exit channel the velocities of molecules in selected states as well as the rotational population distributions in the two lowest vibrational states (ν=0,1) were analyzed for a variety of incoming energies (200 cm−1≤Ekin≤2600 cm−1), scattering angles, and surface temperatures. Molecules with a fast incoming velocity and a rotational energy of Erot≤1000 cm−1 after scattering (about 75% of all molecules) exhibit an elastic interaction with the surface (no energy exchange with the surface, Ekin+Erot=const). For molecules receiving higher rotational energy during the scattering process (Erot≥1000 cm−1) an increasing influence of the surface temperature on their final rotational and translational motion was found. For slow incoming molecules such a dependence is also observed but less pronounced. About 5×10−3 of the incoming molecules are vibrationally excited during their encounter with the surface, and exhibit, after the scattering, angular, and rotational population distributions which are similar to those of the molecules which remain in the vibrational ground state during the scattering process. Rotation of the (110) surface around its normal by 90° leads to identical scattering results: there is no detectable influence of the various surface topographies on the molecular scattering behavior within our present experimental accuracy.