Magnetic coupling between nuclear motion and nuclear spins in molecules

TL;DR

This paper develops a theoretical framework for understanding how nuclear motion couples with nuclear spins in molecules, impacting NMR spectra and revealing new hyperfine interactions.

Contribution

It introduces a comprehensive, electronic-structure-based model for nuclear spin-rotation interactions, including vibrational effects and spin-orbit contributions.

Findings

Nuclear spins can interact with pseudorotational excitations in symmetric molecules.

Infrared light can induce hyperfine splittings observable in NMR spectra.

The framework distinguishes between nuclear spin-orbit and spin-other-orbit effects.

Abstract

Among the possible types of magnetic dipole interactions in molecular systems, couplings between nuclear motion and the nuclear spin have probably received the least attention in molecular spectroscopy. Although very small in comparison to effects related to electron spin, this type of hyperfine interaction plays an important role in the NMR spectroscopy of molecular systems. While measurement and prediction of spin-rotation tensors are a common place, vibrationally induced effects still lack a comprehensive description. In this article we develop a generic, theoretical framework that is well embedded in modern electronic structure theory and inspired by the Breit-Pauli Hamiltonian for electronic interactions, distinguishing between nuclear spin-orbit and spin-other-orbit contributions. We show that the interaction of nuclear spins with pseudorotational excitations of highly symmetric molecules may lead to experimentally accessible hyperfine splittings in NMR spectra, triggered by infrared light.