[en] The behavior of the Goos-Hänchen shifts of the reflected probe light beam at the interface of a three-layer cavity with a three-level Λ-type molecular system is theoretically investigated. The molecular system is HCN→HNC isomerization with nonzero permanent dipole moments (PDMs). The effect of electromagnetically induced transparency (EIT) induced by PDMs in molecules is studied for (1+1)- and (1+2)-transition processes. Thus, the optical response of the medium is modified by the quantum coherence due to nonzero PDMs. Moreover, the reflected probe light field for both transitions experiences superluminal light propagation. Goos–Hänchen shifts of the reflected probe light beam are substantially modified by the refractive index of the interactive medium as well as incident angle. The effect of the coherent coupling field intensity on absorption, dispersion, group index, and the Goos–Hänchen shifts of the reflected probe beam is also discussed. Graphical abstract:

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