# Determination of enantiomeric excess with chirality-dependent AC Stark effects in cyclic three-level models

## TL;DR

This paper proposes a new spectroscopic method to determine enantiomeric excess using chirality-dependent AC Stark effects in cyclic three-level models, avoiding the need for enantio-pure samples and relying solely on electric-dipole transitions.

## Contribution

The method introduces a novel spectroscopic approach based on AC Stark effects that simplifies enantiomeric excess measurement without requiring enantio-pure samples.

## Key findings

- The method can determine enantiomeric excess by analyzing Fourier transform spectra.
- It only involves electric-dipole transitions, enhancing signal strength.
- Applicable to chiral molecules difficult to purify enantiomerically.

## Abstract

Determination of enantiomeric excess is important and remains challenges. We theoretically propose a new spectroscopic method for this issue based on the chirality-dependent AC Stark effects in cyclic three-level models under the three-photon resonance condition. The enantiomeric excess of the chiral mixture is determined by comparing the amplitudes of the two chosen AC Stark peaks in the Fourier transform spectrum of the induced polarizations, which are (approximately) proportional to the molecule numbers of the two enantiomers, respectively. Comparing with current spectroscopic methods based on the interference between the electric- and (usually weak) magnetic-dipole transition moments and/or with the need for enantio-pure samples, our method only involves electric-dipole transitions and does not require the enantio-pure samples. Therefore, it will give strong chiral signals and can be applied to the determinations of enantiomeric excess for chiral molecules whose enantio-pure samples are still challenging to achieve.