EFFECTS OF THERMAL ROUGHENING ON THE ANGULAR-DISTRIBUTIONS OF TRAPPING AND SCATTERING IN GAS-LIQUID COLLISIONS

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 (T-liq) and incident and exit ang les. At temperatures ranging from 280 to 359 K, argon atom energy tran sfer and trapping at the PFPE interface increase steadily with more no rmal approach directions. Trapping also grows with T-liq for all appro ach and exit directions we measured. The fractional change of trapping with T-liq is 2-5 x 10(-3) K-1, rising weakly with more grazing impac t angles. in contrast, the inelastic scattering flux decreases with in creasing T-liq, at forward scattering angles and increases for backwar d deflections. These results are consistent with a surface of protrudi ng hard sphere-like CFx groups that becomes more corrugated at higher temperatures, promoting multiple collisions of incoming atoms at all i mpact angles.