AbstractThis article is concerned with the Stern–Volmer dependence on the NO2, SO2, and CS2fluorescence self‐quenching within a wide range of pressure variations of these gases. Besides, the pressure‐dependences of the photolysis rate of these substances have been investigated. The deviations from linearity in the Stern–Volmer dependences and photolysis rate of NO2, SO2, and CS2in the highpressure region have been revealed. These deviations correspond to increasing effective rate constant of the collision quenching ofexcited molecules NO2, SO2, and CS2.A model to describe the deviations observed has been proposed. The model assumes the formation of excimer particles which may dissociate in a monomolecular way and may be quenched at collisions. The estimates of the lifetimes of excimer particles yield the values of the order of several nano