TEMPERATURE-DEPENDENCE OF THE KINETIC-ENERGY IN CONDENSED ARGON

Using eV neutron scattering, direct measurements have been made of the average single-particle kinetic energies, [E(k)], for a series of con densed Ar samples over the range 18-85 K. These temperature-dependent measurements are on a system with A > 22 amu in the regime below equip artition. The scattering from liquid-Ar samples, for which it is assum ed that [E(k)] can be determined with sufficient accuracy from a quant um expansion, has been used to provide information about the total cor rections to be made to account for neutron time-of-flight spectrometer resolution and multiple scattering. Data were obtained for wave-vecto r transfers in the range 192-254 nm(-1), to check for possible systema tic contributions to experimental uncertainty. The directly measured [ E(k)(T)] is compared to expectations from thermodynamic experiments, f rom previous neutron-scattering measurements of collective vibrational modes of the solid, and from various theoretical models. The directly measured temperature dependence provides evidence for use in the inte rpretation of other experiments which use Ar as an ''inert'' host.