SINGLE-MOLECULE KINETIC-ENERGY OF CONDENSED NORMAL DEUTERIUM

Inelastic scattering of 300-meV neutrons allows the study of the liqui d (T=20 and 30 K, saturated vapor pressure) and solid (T=4.2 K, satura ted vapor pressure) phases of the normal deuterium mixture (2/3 o-D-21/3 p-D-2) in the region of momentum transfer where a single-molecule response is expected. The spectra are analyzed within the impulse appr oximation and assuming Gaussian momentum distributions for the transla tion of the molecules. For the solid, the estimated value of the singl e-molecule average kinetic energy does not compare unfavorably with th ose obtained scaling experimental results in parahydrogen solids. In t he liquid state, substantial departures seem to exist from the classic al liquid behavior, even if up to second-order quantum corrections are taken into account.