Effects of Thermal Roughening on the Angular Distributions of Trapping and Scattering in Gas-Liquid Collisions

Mackenzie E. King, Kathleen M. reenter, and Gilbert M. Nathanson*
Department of Chemistry, University of Wisconsin, 1101 University Ave, Madison, Wisconsin 53706-1322
Tirnothy K. Minton*
Montana State University, Department of Chemistry and Biochemistry, 108 Gaines Hall, Bozeman, Montana 59717
Received. February 28, 1997; In Final Form: May 6, 1997

Abstract

Atomic beam scattering experiments are used to investigate collisions of 71 kJ/mol of argon atoms with perfluorinated polyethers (PFPE) over a wide range of liquid temperatures (Tliq) and incident and exit angles. At temperatures ranging from 280 to 359 K, argon atom energy transfer and trapping at the PFPE interface increase steadily with more normal approach directions. Trapping also grows with Tliq for all approach and exit directions we measured. The fractional change of trapping with Tliq is 2-5 x 10-3 K-1, rising weakly with more grazing impact angles. In contrast, the inelastic scattering flux decreases with increasing Tliq at forward scattering angles and increases for backward deflections. These results are consistent with a surface of protruding hard sphere-like CF.,groups that becomes more corrugated at higher temperatures, promoting multiple collisions of incoming atoms at all impact angles.