On the existence of distinct equilibrium configurations under orienting external electric fields

TL;DR

This paper investigates the existence of multiple stable molecular configurations under external electric fields by leveraging molecular polarizability, revealing new equilibrium states influenced by field orientation.

Contribution

It introduces the concept of 'directomers'—distinct equilibrium configurations arising from electric field orientation and molecular polarizability, expanding understanding of electric field effects on molecules.

Findings

Identification of multiple stable configurations ('directomers') under electric fields.

Development of a hybrid analytical-numerical approach to explore the rotational potential energy surface.

Analytic model capturing the double-well potential and geometry relaxation effects.

Abstract

Oriented external electric fields are ubiquitous in chemistry; however, the effects of fields applied in different directions on molecular systems remain underexplored. A major challenge is that an applied field exerts a torque on a molecule, reorienting the molecular frame and complicating the interpretation of orientation-dependent electric-field effects. Thus, free polar molecules experience orienting rather than oriented fields. In this work, we explore a new regime of distinct molecular equilibrium configurations, differing in the relative direction of the external field and the molecular frame, enabled by exploiting molecular polarizability rather than static dipole moment. These distinct "directomers" exhibit unique electronic and nuclear configurations, particularly in their low-lying excited states. We employ oriented electric field vectors referenced to a molecule-fixed principal axis frame along with hybrid analytical-numerical geometry optimization in order to explore the rotational potential energy surface (rRES), as well as a simply analytic model based on equilibrium electrical properties which captures the double-well character of the rPES, including some geometry relaxation effects.