Non-Dichroic Enantio-Sensitive Chiroptical Spectroscopy

TL;DR

This paper introduces a novel enantiosensitive chiroptical measurement method that detects non-dichroic signals in photoelectron distributions, enabling new ultrafast imaging techniques for chiral molecules.

Contribution

It demonstrates a new type of enantiosensitive signal in photoelectron angular distributions that is not based on dichroism, expanding the toolkit for chiral molecule analysis.

Findings

Enantiosensitive asymmetry encoded in multipolar terms.

Robustness of enantiosensitivity against phase variations.

Potential for ultrafast chiral molecule imaging.

Abstract

Chiroptical effects using circularly polarized light produce signals that change sign when switching either molecular handedness (enantiosensitivity) or the light helicity (circular dichroism). Here, we break this enantiosensitive-and-dichroic paradigm by measuring a new type of chiroptical signal which is enantiosensitive but not dichroic. We photoionize chiral molecules using a strong laser field and detect the three-dimensional photoelectron momentum distribution. The non-dichroic, enantiosensitive asymmetry is encoded in octupolar and higher multipolar terms in the photoelectron angular distribution, which appear in multiphoton ionization with elliptically polarized fields or cross polarized two-color fields. The robustness of the enantiosensitivity with respect to the relative phase between the vectorial components of the ionizing field represents an example of symmetry protection, and opens unexplored opportunities for imaging ultrafast dynamics in chiral molecules, such as enantiosensitive photoelectron spectroscopy with bright squeezed vacuum states.