Enhancement of parity-violating energy difference of CHFClBr, CHFClI, and CHFBrI by breaking the cancellation among valence orbital contributions

TL;DR

This paper investigates how electronic excitation can significantly enhance the parity-violating energy difference (PVED) in certain chiral molecules by breaking the cancellation among valence orbital contributions, especially focusing on CHFClBr, CHFClI, and CHFBrI.

Contribution

It introduces the concept of cancellation breaking enhancement, explaining how excited states can amplify PVED by disrupting orbital contribution cancellations, and confirms this mechanism for specific molecules.

Findings

PVED increases in excited states due to cancellation breaking.

HOMO contribution dominates PVED enhancement.

Estimation of PVED in excited states from HOMO contribution.

Abstract

The enhancement of the parity-violating energy difference (PVED) by electronic excitation is studied for H$_2X_2$ ($X =$ O, S, Se, Te), CHFClBr, CHFClI, and CHFBrI. To clarify the enhancement mechanism, the dihedral angle dependence of the PVED of H$_2X_2$ in excited states is studied. If the contribution from the highest occupied molecular orbital (HOMO) to the PVED in the ground state is larger than the sum of those from all occupied orbitals, the PVED in the first excited state has a much larger value compared to the ground state due to cancellation breaking among valence orbital contributions. This enhancement is named cancellation breaking enhancement. The PVED enhancement is also studied for CHFClBr, CHFClI, and CHFBrI in excited states, and the cancellation breaking enhancement is confirmed. When the PVED contribution from the HOMO is larger than any other contribution, the cancellation breaking enhancement hypothesis provides the estimate of PVED in the first excited state from the HOMO contribution.