This paper is the third of three papers on the kinetics of particle-beam-generated molecular plasmas. In the first paper we derived a general formalism for the inversion of the Boltzmann high-energy operator in this kind of molecular plasma. In the second paper we applied and modified this general formalism to the interesting particular case of 0,, taking into account the low threshold excitation of metastable modes. In this third paper we complete this kinetic investigation by an analysis of the Boltzmann low-and mediumenergy equation available for any stationary particle-beam-generated molecular (or atomic) plasma, including all inelastic processes. Use of this analysis together with the moment conservation equations provides a means to obtain analytically the electron density and 'temperature' in the plasma. Theoretical results are compared with experimental parameters measured in 0, by Pointu and Zeller at Orsay, with gun jet electrons, and orders of magnitude are in good agreement when diffusion is taken into account.