Collective excitations in liquid methanol studied by coherent inelastic neutron scattering

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Abstract
Inelastic spectra of deuteromethanol measured by triple-axis neutron spectroscopy at several temperatures within the liquid range are reported. The observed scattering intensities are analysed in terms of reconstructions of the dynamical structure factor after deconvolution from instrumental effects, as well as model fits to the measured intensities. The data indicate the existence of a propagating high-frequency excitation, which at T=200 K becomes overdamped for wavevectors Q>0.6 AA-1. An insight into the nature of the observed excitation is given by the temperature behaviour of the damping factors. Such a trend gives additional support to the assignment of the excitation to closely packed patches of hydrogen-bonded molecules.