Self-Diffusion of Liquid Normal Hydrogen: A Quasi-Elastic Neutron Scattering Study*

Quantum zero-point motion plays an important role in determining the properties and behavior of liquid hydrogen. For example, by comparing the predictions of classical molecular dynamics with centroid molecular dynamics, several theoretical studies have suggested that the self-diffusion constant of liquid para-hydrogen is dominated by zero-point motion. In this presentation, we report quasi-elastic neutron scattering measurements of liquid normal hydrogen under saturated vapor pressure. Our empirical estimates of the self-diffusion constant and Arrhenius activation energy are in good agreement with accepted values obtained by nuclear magnetic resonance. As previous theoretical work has generally focused upon temperatures near the triple point, we will argue that further development in this area would be useful.