Observation of scalar nuclear spin-spin coupling in van der Waals molecules

TL;DR

This paper reports the first observation of scalar nuclear spin-spin couplings in van der Waals molecules, using hyperpolarized xenon and pentane in low magnetic fields, opening new avenues for probing weak intermolecular forces.

Contribution

It demonstrates the detection of scalar couplings in unbound van der Waals complexes, a phenomenon previously unobserved, combining experimental measurements with theoretical calculations.

Findings

Scalar couplings observed in van der Waals molecules.

Good agreement between experiments and density functional theory.

Potential new method for probing weak intermolecular interactions.

Abstract

Scalar couplings between covalently bound nuclear spins are a ubiquitous feature in nuclear magnetic resonance (NMR) experiments, imparting valuable information to NMR spectra regarding molecular structure and conformation. Such couplings arise due to a second-order hyperfine interaction, and, in principle, the same mechanism should lead to scalar couplings between nuclear spins in unbound van der Waals complexes. Here, we report the first observation of scalar couplings between nuclei in van der Waals molecules. Our measurements are performed in a solution of hyperpolarized ${\rm ^{129}Xe}$ and pentane, using superconducting quantum interference devices to detect NMR in 10 mG fields, and are in good agreement with calculations based on density functional theory. van der Waals forces play an important role in many physical phenomena, and hence the techniques presented here may provide a new method for probing such interactions.