AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA8
Influence of Rotational Energy on Adsorption Probability for a Physisorbed System: C2H4 on Ag(001)

Wednesday, October 27, 1999, 4:20 pm, Room 607

Session: Gas-Surface Dynamics
Presenter: M. Rocca, University of Genova, INFM, CSFBT-CNR, Italy
Authors: M. Rocca, University of Genova, INFM, CSFBT-CNR, Italy
Luca Vattuone, University of Genova, INFM, CSFBT-CNR, Italy
U. Valbusa, University of Genova, INFM, CSFBT-CNR, Italy
Correspondent: Click to Email
We show that the population of the rotational degrees of freedom of gas molecules affects their adsorption probability also for a physisorbed state. The effect, expected to be very general, is demostrated for the case of ethylene interaction with Ag(001) where we observe that the physisorption probability is suppressed for molecules produced with a hot nozzle, characterized by a sustantially larger rotational quantum number. Chemisorption of ethylene is observed for nozzle temperatures above 870 K and occurs in two phases characterized by different vibrational electron energy loss spectra. The barrier to chemisorption is in the vibrational degree of freedom as can be inferred by comparing pure and seeded beam data. At still larger nozzle temperatures fragmentation of ethylene upon adsorption is observed.