Time resolved laser induced fluorescence applied on low pressure surface wave discharge : studying the argon excitation kinetics

In this contribution we report the application of time resolved laser induced fluorescence (tr-LIF) experiments on low pressure surfatron plasmas with pure argon and argon mixed with molecules (O2, N2 and H2). In this technique a tuneable dye laser can be used to perturb one particular excited level, obtaining information from the response to the perturbation. In our experimental setup a high repetition rate Nd:YAG laser is used to induce the dye emission, increasing substantially the output intensity and reducing the measuring time. In this experimental study we pump different excited levels of the argon system, always from the argon metastable group. Studying the decay time of the fluorescence signal for different plasma conditions in combination with precise Thomson scattering measurements of the electron density, enable us to obtain the rates for the collisional processes that depopulate the levels, namely the heavy particle quenching and the inelastic electron-atom collisions rate. Simultaneously, trLIF measurements give information about the populations of the bottom level of the perturbed, providing spatial distributions of the argon metastable levels along the plasma. Finally, the response to the laser perturbation of different excited argon levels apart from the perturbed one, or even the response of different species (H, N, O radicals) can also give information about the interactions in the excitation space