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

We have measured the inelastic neutron scattering from solid parahydrogen at molar volumes from 23.2 to 17.0 cm3. We observe peaks in the differential cross section d2/d 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 cm3/mole we find kinetic energies per particle of 77 3, 101 8, 122 14, 131 14, and 146 11 K, respectively.