Geometrical terms in the effective Hamiltonian for rotor molecules

TL;DR

This paper introduces new centrifugal distortion terms in the effective Hamiltonian for asymmetric rotor molecules, drawing an analogy with anisotropic cosmology, and highlights their significance in molecules like methanol.

Contribution

It derives novel geometrical terms in the effective Hamiltonian for asymmetric rotor molecules, especially those lacking internal 3-fold symmetry, using an analogy with anisotropic cosmology.

Findings

New centrifugal distortion terms identified for asymmetric rotors.

Extra $ ext{cos}\alpha$ and $ ext{cos}2 ext\alpha$ contributions quantified.

Corrections are comparable to isotope substitution effects.

Abstract

An analogy between asymmetric rotor molecules and anisotropic cosmology can be used to calculate new centrifugal distortion terms in the effective potential of asymmetric rotor molecules which have no internal 3-fold symmetry. The torsional potential picks up extra $\cos\alpha$ and $\cos2\alpha$ contributions, which are comparable to corrections to the momentum terms in methanol and other rotor molecules with isotope replacements.