Quasi-elastic neutron scattering of dense molecular liquid selenium bromide

Quasi-elastic neutron scattering spectra of liquid Se2Br2 at 298 K, 373 K and 473 K were measured by utilizing the cold-neutron disk-chopper spectrometer AMATERAS in J-PARC. The obtained dynamic structure factors are reproduced well by a two-Lorentzian model consisting of slow and fast modes. With increasing temperature, the maxima in the Q-dependence of the magnitude for both modes shift to a low Q direction, while the temperature dependence of the magnitude is opposite between slow and fast modes. The temperature dependence of the magnitude and the analysis of the energy width for these modes reveal that the fast mode is originated from dynamics in strongly interacted neighbouring molecules, while the slow mode is derived from inter-molecular dynamics without the strong interaction.