Density dependence of the single-particle kinetic energy of solid hydrogen

Abstract

We have measured the inelastic neutron scattering from solid parahydrogen at molar volumes from 23.2 to 17.0 ${\mathrm{cm}}^{3}$. We observe peaks in the differential cross section ${d}^{2}$\ensuremath{\sigma}/d\ensuremath{\Omega} dE corresponding to internal molecular transitions from ground to excited rotational and vibrational states. From the widths of these peaks we determine the center-of-mass translational energy per molecule using an underlying Gaussian momentum distribution for the initial center-of-mass translational wave function. For volumes of 23.2, 21.3, 19.5, 18.2, and 17.0 ${\mathrm{cm}}^{3}$/mole we find kinetic energies per particle of 77\ifmmode\pm\else\textpm\fi{}3, 101\ifmmode\pm\else\textpm\fi{}8, 122\ifmmode\pm\else\textpm\fi{}14, 131\ifmmode\pm\else\textpm\fi{}14, and 146\ifmmode\pm\else\textpm\fi{}11 K, respectively.