Quantum calculation of inelastic neutron scattering spectra of a hydrogen molecule inside a nanoscale cavity based on rigorous treatment of the coupled translation-rotation dynamics

Abstract

We present a quantum methodology for the calculation of the inelastic neutron scattering (INS) spectra of an ${\mathrm{H}}_{2}$ molecule confined in a nanoscale cavity. Our approach incorporates the coupled five-dimensional translation-rotation (TR) energy levels and wave functions of the guest molecule. The computed INS spectra are highly realistic and reflect in full the complexity of the coupled TR dynamics on the anisotropic potential energy surfaces of the confining environment. Utilizing this methodology, we simulate the INS spectra of $p$- and $o$-H${}_{2}$ in the small cage of the structure II clathrate hydrate and compare them with the experimental data.