Aligned molecules: chirality discrimination in photodissociation and in molecular dynamics

Emergence of biochemical homochirality is an intriguing topic, and none of the proposed scenarios has encountered a unanimous consensus. Candidates for naturally occurring processes, which may originate chiral selection, involve interaction of matter with light and molecular collisions. We performed and report here: (1) simulations of photodissociation of an oriented chiral molecule by linearly polarized (achiral) light observing that the angular distribution of the photofragments is characteristic of each enantiomer and both differ from the racemic mixture; and (2) molecular dynamics simulations (elastic collisions of oriented hydrogen peroxide, one of the most simple chiral molecules, with Ne atom) demonstrating that the scattering and the recoil angles are specific of the enantiomeric form. The efficacy of non-chiral light (in the case of photodissociation) and of non-chiral projectile (in the case of collisions) is due to the molecular orientation, as an essential requirement to observe chiral effects. The results of the simulations, that we report in this article, provide the background for the perspective realization of experiments which go beyond the well-documented ones involving interaction of circularly polarized laser (chiral light) with the matter, specifically by making use of non-chiral, i.e. linearly polarized or unpolarized light sources, and also by obtaining chiral effects with no use at all of light, but simply inducing them by molecular collisions. The case of vortices is discussed in a companion paper. © 2013 Accademia Nazionale dei Lincei.