Low-temperature infrared spectroscopy of H$_2$ in solid C$_{60}$

Diffuse reflectance infrared spectroscopy was used to probe the quantum dynamics of H$_2$ trapped in a C$_{60}$ lattice. Because free H$_2$ is infrared inactive, features of the infrared spectra are induced solely through interactions with the host material and as such provide detailed information about the potential at the binding site. The design and construction of a cryogenic apparatus allowed the extension of previous room temperature measurements to temperatures as low as 10 K at pressures as high as 100 atm. The low temperature spectra contained much sharper peaks and a rich fine structure, enabling more precise determination of the details of the C$_{60}$-H$_{2}$ interaction potential. These studies of H$_2$ in C$_{60}$ inform hydrogen storage materials research in a broader context, as illustrated by the diffuse reflectance spectra of H$_2$ in MOF-5.