Orienting and aligning molecules for stereochemistry and photodynamics

Production, characterization and control of polarization states of molecules (specifically, alignment and/or orientation) are of importance for investigating in detail the stereodynamics of elementary processes involving elastic, inelastic and reactive events and also to prepare targets for selective photodynamical investigations. The focus here is on those molecular beam techniques which show perspectives in the applications offering appealing features for ‘‘duty cycle’’ and intensity characteristics. After a review of the basic experimental advances, mainly obtained in the last ten years, the attention will be addressed to recent studies carried out on the collisional alignment of hydrocarbon molecules and on orientation of symmetric top molecules by exploiting honeycomb hexapole fields. The first case is a prototype of ‘‘natural’’ polarization techniques, the second one of those where polarization is ‘‘forced’’ by external fields.