Conformational effects in photoelectron circular dichroism

PhotoElectron Circular Dichroism (PECD) is a novel spectroscopy that presents surprising sensitivity to conformational effects in chiral systems. While classical PhotoElectron Spectroscopy responds to conformational effects mainly in terms of energy level shifts, PECD provides a rich and detailed response to tiny changes of the electronic and structural properties by means of the dispersion of the intensity of the circular dichroism as a function of photoelectron kinetic energy. In this work PECD basics will be outlined emphasizing the role of the interference of the l,l±1 outgoing partial wave of the photoelectron in the PECD transition matrix element, that is responsible of the extreme sensitivity to conformational effects. Examples on molecular systems and interfaces will shade light on the powerful application of PECD to classical conformational effects such as group substitution, isomerism, conformer population, clustering. Moreover PECD results in new challenging fields where conformations play a key role, such as vibrational effects, transient chirality, time resolved experiments, will be reported. To date PECD is mostly based on synchrotron radiation facilities, but it has a future as a lab table-top experiment by means of multi-photon ionisation. An important application of PECD as an analytical tool will be reported. The aim of the review is to illustrate that in PECD the conformational effects are essential to understand a wide range of effects from a new perspective, different from classical spectroscopy.