SPECTRAL FREQUENCY-DISTRIBUTION FOR LIQUID DEUTERIUM DETERMINED BY NEUTRON-SCATTERING

The generalized spectral distribution, which is the frequency-domain r epresentation of the velocity autocorrelation function, is determined for liquid molecular deuterium for a broad range of frequencies from n eutron-scattering experiments. Two well-defined features centered at f requencies of 3.8 and 7.6 meV are seen superimposed on a broad, slowly decaying tail. The latter seems reminiscent of what has been observed for hydrogen in the dense-gas phase whereas the former is shown to ar ise from finite-frequency collective excitations and quantized molecul ar rotations.