  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.
