The semiclassical limit of the intermediate scattering function

We point out the existence of an oversimplification in a previously derived semiclassical limit for the intermediate scattering function and present a new derivation of the result. The new formula is similar to the previous one and maintains its symmetry properties (i.e. detailed balance). Unfortunately, our expression also contains a new factor, related to the Maslov index of the trajectories appearing in it, that prevents its numerical implementation.