Direct connection between collisional Raman cross sections and state-to-state rotational ones permits, within the sudden approximation, to evidence drastic decouplings from isotropic to anisotropic lines. These decouplings are consistent with the results obtained by using the strong collision model. Convenient energy corrections to the sudden approximation are used for N2 to calculate the resulting effects on the isotropic and anisotropic Q-branch profiles in a large density range (several hundred bars). The comparison of the calculations with experimental coherent anti-Stokes Raman scattering (CARS) and stimulated Raman (SRS) spectra of nitrogen exhibits a good agreement. Such effects could have applications in optical diagnostics.