We propose a simple semi-empirical method to calculate cross
sections and rate coefficients for thermal dissociation of diatomic molecules by electron impact. It is an improvement of Bacri's work /1/ based upon the calculation of weighted total cross sections (WTCS) which is able to take into account predissociation processes. This method is valuable for any electronic state (fundamental as well as excited). An application to the main molecules of air (N2, 02, NO and their positive ions) is given and the
computed reaction rates are compared, when possible, with other bibliographical references.