Internal energy dependence of molecular condensation coefficients determined from molecular beam surface scattering experiments

An experiment was performed which confirms the existence of an internal mode dependence of molecular sticking probabilities for collisions of molecules with a cold surface. The scattering of a velocity selected effusive beam of CCl4 from a 90 K CC14 ice surface has been studied at five translational velocities and for two different internal temperatures. At a surface temperature of 90 K (approx. 99% sticking probability) a four fold increase in reflected intensity was observed for the internally excited (560 K) CC14 relative to the room temperature (298 K) CC14 at a translational velocity of 2.5 X 104 cm/sec. For a surface temperature of 90 K all angular distributions were found to peak 150 superspecularly independent of incident velocity. 9 references