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{σ}/d{Ω} 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.