Investigation of photoelectron elliptical dichroism for chiral analysis

Abstract

This paper describes a compact new instrument, conceived specifically for measurements of Photo Electron Elliptical Dichroism (PEELD) and designed for simplicity of use as a prototype for a practical analytical device. PEELD is an asymmetry in the electron angular distribution obtained from resonantly enhanced multi-photon ionisation of a chiral molecule, where there is also a non-linear dependence on the polarization ellipticity. Despite the fact that PEELD can provide a unique signature of molecular structure and dynamics it has only been investigated in a few molecules to date. This is addressed in the present study in a range of measurements of several terpenes and phenyl-alcohols. These show that the PEELD signatures in structural isomers can be dramatically different and can also be influenced by the intensity of the light. A systematic study in phenyl-alcohols containing the same chromophore and chiral centre configuration shows consistent PEELD behaviour across the molecules except that the magnitude reduces as the distance from the chromophore to the chiral centre increases. These achievements demonstrate that this relatively simple set up can be used for scientific studies as well as providing a blueprint for a practical chiral analysis instrument.