Study of low-temperature uranium plasmas not within local thermodynamical equilibrium

A collisional-radiative model constituted by statistical equilibrium equations has been built up, the considered atomic levels of U I and U II being coupled by the elementary processes; while the electronic temperature T e and density n e are fixed with T e <or=5 eV and n e >or=10 10 cm -3 . It is assumed that the plasma is stationary, optically thin and that the electrons are Maxwellian. Absolute oscillator strengths of U I and U II transitions are derived using the published radiative lifetimes and branching ratio values obtained mainly by the laser induced fluorescence (LIF) method. It is found that the previously published U II gf values are underestimated by a mean factor of 2.8. The results derived by the model against T e and n e are the relative populations of the U I and U II fundamental and metastable levels, the relative densities of the atomic and ionic species U I, U II and U III, the excitation temperatures of U I and U II and the radiative power loss.