Transvers THz Dynamics of Phospholipid Membranes, a Neutron Scattering Study

The off-plane dynamics in the frequency window from 1 THz (4 meV) to 3 THz (12 meV) in multiple phospholipid bilayers as studied by means of neutron scattering is presented. A weak inelastic signal is observed, indicating that off-plane dynamics is dominated by the disordered inter-layer water. A collective mode is detected which shows a low-momentum dispersion similar to that of bulk water, while a more complex dynamics is found on increasing the momentum transfer.