A modeling of the photoplasma in a slab cell filled with a sodium vapor and argon mixture one-sided irradiated by a uniform radiation flux was carried out. This study was performed for a spatially heterogeneous distribution of the resonance level density, unlike our previous works. An analytical form of this distribution for the slab available in the literature was used. The present investigation was performed at the sodium vapor pressure PNa=0.0050.3 torr and the ratio of argon and sodium pressures PAr/PNa=102 for the spectral flux density F=51025.2104 Wm2nm1. A set of plasma chemical reactions, radiation transfer and charge transport were considered. The spatial profiles of densities of the sodium atomic levels, atomic and diatomic ions, the electron density and temperature, and the electric potential in the volume of the cell were obtained from a self-consistent solution of the balance equations for densities of plasma components and the electron energy. It was established that spatial picture of the Na+ and Na2+ ion density fractions depends significantly on the cell conditions. Parameters of wall sheaths were calculated used formulas from the literature. Used these data and the obtained spatial profiles of electric potential, the dependencies of electromotive force (the potential difference between the illuminated and dark walls of the cell) on the sodium pressure and incidental spectral flux density were obtained. The maximal EMF value was 1.5 V for the PNa=0.05 torr and F=5.2104 Wm2nm1. Obtained results can be used in the development of photo-electric converters.