Quasi-elastic neutron scattering of dense molecular liquid selenium bromide

Shimakura, Hironori; Kawakita, Yukinobu  ; Inamura, Yasuhiro  ; Kikuchi, Tatsuya  ; Ueno, Hiroki; Nakamura, Mitsutaka   ; Nakajima, Kenji   ; Kawamura, Seiko   ; Shibata, Kaoru*; Arai, Masatoshi; Takeda, Shinichi*

Liquid selenium bromide consists of Br-Se-Se-Br molecules, where a strong inter-molecular correlation exists so that Se-Se bond is parallel to that in neighboring molecules. Quasi-elastic neutron scattering (QENS) of SeBr was performed by cold-neutron disk-chopper spectrometer in J-PARC. Multi Ei measurement with incident energies of 3.13, 7.72 and 41.83 meV was applied. It is found that QENS can be well fitted by two Lorentzian components corresponding slow and fast relaxation modes. Integral intensity of slow component shows a maximum value at around 1.6 at room temperature and shifts to lower Q direction with increasing temperature. This shift relates to density decrease. In opposite, the HWHM of the latter has so-called de Gennes narrowing and this Q position shifts to lower Q direction with increasing temperature. This mode relates to neighboring-molecular correlation because narrowing generally occurs at Q position which exhibits strong correlation.