[en] A collisional radiative (C-R) model is used to obtain the number densities of the ground level and of the excited levels of neutral argon as a function of the local nsub(e) and Tsub(e) values. This model is first applied to a homogeneous and stationary medium for 5000 K < Tsub(e) < 12,000 K. The local values of the density of atoms in the ground level and of the heavy particles (neutrals and ions) temperature Tsub(g) in a non-LTE discharge are determined. The C-R model is then applied to the positive column of a stationary argon arc. The ambipolar flux of electrons is evaluated and compared to the net rate of electron production. In the outer region of the arc column, for lower nsub(e) and Tsub(e) values, it is absolutely necessary to take into account atom-atom collisions in order to satisfy the balance equation deltansub(e)/delta t = 0 for electrons. (author)