In the energy range of interest for x‐ray lithography, absorption of x rays by atoms results in the emission of photoelectrons and Auger secondary electrons, as well as a shower of low energy electrons. The development of accurate image formation models in x‐ray lithography requires that these mechanisms be included. The photoelectron processes produce a redistribution of the x‐ray energy over a finite volume. The interaction of the electrons with the medium is complex and can be treated in the framework of a response theory (dielectric function). A simulation code, based on the Monte Carlo method (lesis), has been developed to study the photon energy redistribution in resists, in the vicinity of resist–substrate interfaces and overlayers. The low computational efficiency of the Monte Carlo method motivates the need to parametrize the energy redistribution results of the simulation. This parametrization was performed for a polymethyl‐methacrylate/Si interface, as a function of the photon energy. The parametrization can be interpreted as the weighted sum of individual electron responses. The effects on the resist of photoelectrons generated in the substrate are discussed. These effects have been incorporated in an effective dose model that can be used to compute complex interface geometries. The results are particularly relevant for the nanolithography domain (<100 nm).