Interaction of rotationally aligned and of oriented molecules in gas phase and at surfaces

• Published in: Progress in surface science Vol. 85; no. 1; pp. 92 - 160
• Main Authors: Vattuone, L., Savio, L., Pirani, F., Cappelletti, D., Okada, M., Rocca, M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2010; Elsevier
• Subjects: Atomic and molecular collision processes and interactions; Atomic and molecular physics; Chemical reactions; Chemistry; Exact sciences and technology; Gas-surface interactions; General and physical chemistry; General, apparatus; Heterogeneous catalysis; Interactions of atoms, molecules and their ions with surfaces; photon and electron emission; neutralization of ions; Physics; Scattering of atoms, molecules and ions; Stereodynamics; Surface and interface chemistry; Surface physical chemistry; Heterogeneous catalysis; Chemical reactions; Stereodynamics; Gas-surface interactions; Alignment; Reviews; Molecular orientation; Spatial distribution; Steric effect; Gas surface interaction; Molecular beams; Gas phase
• ISSN: 0079-6816; 1878-4240
• DOI: 10.1016/j.progsurf.2009.12.001

Recent developments concerning the generation of molecular beams containing oriented/aligned molecules will be reviewed and applications of such tools to the study of elementary processes occurring both in homogeneous and heterogeneous phases will be presented. First we will discuss the case of symmetric top molecules oriented by hexapoles. Here the molecular polarization is obtained by the use of an external field and allows to control which end of the molecular projectile is going to collide with the target. Then we will review the so-called collisional alignment, a molecular polarization phenomenon occurring in supersonic expansions of gaseous mixtures. The key feature, in this case, is the velocity dependence of the alignment degree, which allows the use of mechanical devices to filter out of the beam the molecules having either a random (statistical) or a preferential (non-statistical) spatial distribution of their rotational angular momentum J with respect to the molecular beam axis. The physical mechanisms underlying the collisional alignment will be resumed and some relevant gas-phase experiments demonstrating its occurrence will be illustrated. Application of such methodologies to the investigation of the stereodynamics of elementary processes occurring in gas-surface interaction will be presented and discussed for both weakly and strongly interacting systems.