Reflectivity of a nonlocal dielectric with an excitonic surface potential

The reflectivity of a semi-infinite nonlocal dielectric is investigated theoretically, including the effect of the surface potential and without invoking the simplifying dead-layer approximation. This is achieved by integrating the exciton equation of motion in the presence of the repulsive, spatially varying, surface potential together with Maxwell's equations. The method is developed for both $s$ and $p$ polarizations, and the results of numerical calculations of the reflectivity of CdS and ZnSe are presented.