  The density correlation function F(q,t) of the two similar substituted
aromatic liquids, Toluene and m-Toluidine, is studied by coherent neutron
spin-echo and time-of-flight scattering for wave vectors q around the maximum
q_max of the total static structure factor S_m(q) in the supercooled i.e. high
density state far away from the normal fluid state. The wave-vector dependence
of the mean structural relaxation time tau shows in both liquids a very
pronounced de Gennes-like narrowing centered around q_0 < q_max, where q_0
corresponds to the first maximum in the center-of-mass static structure factor
S_COM}(q). We find that the narrowing can be described quantitatively by using
S_COM(q)/q^2 instead of S_m(q)/q^2 indicating that at the corresponding
molecular length scales the relaxation of F(q,t) is dominated by purely
translational motion.
