Circular dichroism in the photoelectron angular distribution of achiral molecules

TL;DR

This study investigates circular dichroism in photoelectron angular distributions of achiral molecules, revealing that the final state of the photoelectron is the key source of CDAD, with implications for understanding electronic structure effects.

Contribution

It demonstrates that the photoelectron's final state causes CDAD in achiral molecules, supported by experimental data and theoretical modeling, including a simple scattering model.

Findings

Final state of photoelectron is the source of CDAD in achiral molecules.

Comparison of experimental maps with DFT simulations elucidates the mechanism.

A scattering model decomposes CDAD into partial wave contributions.

Abstract

Circular dichroism in the angular distribution (CDAD) is the effect that the angular intensity distribution of photoemitted electrons depends on the handedness of the incident circularly polarized light. A CDAD may arise from intrinsic material properties like chirality, spin-orbit interaction, or quantum-geometrical effects on the electronic structure. In addition, CDAD has also been reported for achiral organic molecules at the interface to metallic substrates. For this latter case, we investigate two prototypical $\pi$-conjugated molecules, namely tetracene and pentacene, whose frontier orbitals have a similar shape but exhibit distinctly different symmetries. By comparing experimental CDAD momentum maps with simulations within time-dependent density functional theory, we show how the final state of the photoelectron must be regarded as the source of the CDAD in such otherwise achiral systems. We gain additional insight into the mechanism by employing a simple scattering model for the final state, which allows us to decompose the CDAD signal into partial wave contributions.