DYNAMICS IN VISCOUS ORTHOTERPHENYL - RESULTS FROM COHERENT NEUTRON-SCATTERING

We have measured coherent neutron scattering from deuterated orthoterp henyl on a spin echo and a backscattering spectrometer. In agreement w ith mode coupling theory, pair correlations decay in two steps and fol low the same scaling laws as those found previously for self-correlati ons, The temperature evolution of the intermediate plateau is compatib le with the previously established T-c=290 K. The spatial resolution h as not been sufficient to fully resolve oscillations of parameters as functions of Q, which are predicted by mode coupling theory. Within th is limitation, we find that the double peak structure of S(Q) is not e xpressed in the nonergodicity parameter f(Q)(c) and that the de Gennes narrowing is missing.