Multidimensional tunnelling of molecules aligned by strong electric fields
Abstract
Strong electric fields can be used to align molecules. However, a non-polar molecule such as H has no preference for its orientation. There are thus two equivalent configurations with equal energy separated by a potential-energy barrier. Quantum mechanically, the molecule can tunnel between these configurations resulting in a tunnelling splitting, which in the case of H, is the same as the ortho--para splitting. In this work, we generalize semiclassical instanton theory to calculate the energy splitting of molecules in electric fields in full dimensionality. This goes beyond a perturbative treatment of the field and takes into account changes in molecular geometry during the tunnelling process which influence its electrical properties and can have a significant impact on the result. We first study the case of H in a static electric field and then show how it can be applied to larger polar molecules subjected to oscillating electric fields, where we find that even large-amplitude heavy-atom tunnelling can lead to observable splittings.
Cite
@article{arxiv.2512.01714,
title = {Multidimensional tunnelling of molecules aligned by strong electric fields},
author = {J. Amira Geuther and Marit R. Fiechter and Jeremy O. Richardson},
journal= {arXiv preprint arXiv:2512.01714},
year = {2025}
}