Dynamics in viscous orthoterphenyl: Results from coherent neutron scattering

We have measured coherent neutron scattering from deuterated orthoterphenyl on a spin echo and a backscattering spectrometer. In agreement with mode coupling theory, pair correlations decay in two steps and follow the same scaling laws as those found previously for self-correlations. The temperature evolution of the intermediate plateau is compatible with the previously established ${\mathit{T}}_{\mathit{c}}$=290 K. The spatial resolution has not been sufficient to fully resolve oscillations of parameters as functions of Q, which are predicted by mode coupling theory. Within this limitation, we find that the double peak structure of S(Q) is not expressed in the nonergodicity parameter ${\mathit{f}}_{\mathit{Q}}^{\mathit{c}}$ and that the de Gennes narrowing is missing.