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We previously derived a theorem about the {\em coherent} quasielasticneutron-scattering signal from a $d$-dimensional lattice of $N$ molecules thatare undergoing rotational jump diffusion (around an $n$-fold axis), assumingthat there are no correlations between the molecules. In the present papermolecular correlations are treated, but only in the sense that severalmolecules could reorient simultaneously as in a cog-wheel mechanism. Moreover,we do not examine the possibility that the relaxation times of these combinedreorientations could depend on details of the local environment created by theneighbouring molecules. Finally also an ergodicity condition has to befulfilled. Admitting for all these assumptions we can show that thecorrelations do not affect the coherent quasielastic scattering pattern in thefollowing sense: The functions of $Q$ that intervene in the description of theintensities remain unaltered, while the functions of $\omega$ can undergo arenormalization of the time scales. The latter changes cannot be detected asthe time scales that would occur if the dynamics were independent are notavailable for comparison. In other words: Coherent quasielastic neutronscattering is not able to betray the existence of correlations of therestricted type that occur in our model.Comment: 15 pages, 0 figure

Coherent quasielastic neutron scattering and correlations between rotational jumps of molecules on a periodic lattice