Al28 Surface Science 126 ( 1983) 641-646 North-Holland Publishing Company
641
THERMAL ENERGY HELIUM VERY LOW COVERAGES Bene POELSEMA, George COMSA
Robert
Instrtutf;r Grenrfl&henforschung
SCATTERING
L. PALMER und Vakuumphysik.
FROM
CO/Pt(lll)
*, Siebe T. DE ZWART Kernforschungsanlage
AT
and
Julich, D
.5170Jiihch,
Fed. Rep. of German.v Received
24 August
1982; accepted
We report on thermal shown to be dominated scattering cross section incident He atoms and be understood in terms measured at different refractive and geometric
for publication
26 October
1982
He scattering from CO/Pt( 111)at low coverages (8,, < 0.01) which was by long-range ottracriue forces centered at the adsorbed CO molecules. The of adsorbed CO is measured as a function of both the velocity of the the angle of incidence. In first approximation the angular dependencies can like” effects. The velocity dependencies, of simple geometric “shadowing angles of incidence, coincide on a universal curve after correction for effects.
647
Surface Science 126 (1983) 647-653 North-Holland Publishing Company
SIMULTANEOUS EXCITATION OF ROTATIONS AND SURFACE PHONONS IN THE SCATTERING OF D, FROM A NaF CRYSTAL G. BRUSDEYLINS Max - Planck Germany Received
and J. Peter TOENNIES
Institut fib Strdmungsforschung,
23 August
B6ttingerstrasse
4 - 8. D - 3400 G&mgen,
Fed. Rep. of
1982
Angular distributions and time-of-flight spectra have been measured for the scattering of n-D, from NaF(OO1) along the (100) direction at energies between 30 and 90 meV. The angular distributions reveal, in addition to the elastic diffraction peaks, additional sharp peaks due to the show rotational transitions 0 + 2, 1-+ 3, and 0 + 4. The relative rotational transition probabilities an anomalous behavior which can in part be explained by a kinematic rainbow. An enhancement of rotational transitions in grazing collisions (large 8,) is also observed. The time of flight spectra confirm the assignments and reveal that phonon processes also are occurring simultaneously with the rotational transitions.