Absorption of an electron by a dielectric wall

We introduce a method for calculating the probability with which a low-energy electron hitting the wall of a plasma gets stuck in it and apply the method to a dielectric wall with positive electron affinity smaller than the bandgap using MgO as an example. In accordance with electron beam scattering data we obtain energy-dependent sticking probabilities significantly less than unity and question thereby for electrons the perfect absorber assumption unisono used in plasma modeling.