Stereodynamic effects in the adsorption of propylene molecules on Ag(001).
We report on the experimental evidence of the role of rotational alignment of the gas-phase molecules in the interaction of propylene with Ag(001). Molecular alignment has been controlled by a velocity selection of the impinging molecules, flying in a supersonic seeded molecular beam. The experimental findings indicate that at low surface coverage the sticking probability is independent of molecular alignment, while when coverage exceeds few percent of a monolayer, molecules impinging rotating parallel to the surface (helicopter-like configuration) achieve a higher chance to be trapped than those which impinge rotating perpendicularly (cartwheels). The sudden appearance of a large stereodynamic effect suggests that the adsorption proceeds via a mobile precursor state and is tentatively correlated with a change in the configuration of the added propylene molecules, which adsorb tilted rather than flat at the surface.
Gerbi
A
A
Dipartimento di Fisica, Universita Genova, Via Dodecaneso 33, Genova, Italy.
Vattuone
L
L
Rocca
M
M
Pirani
F
F
Valbusa
U
U
Cappelletti
D
D
Vecchiocattivi
F
F