Oscillating convective effects in SF₆-Ar laser-heated mixtures

Periodic temperature variations were observed in vertical absorption cells which were filled with mixtures of SF₆ and Ar. The cells were irradiated from below with a continuous CO₂ laser beam of moderate intensity (3-15 W). The onset of oscillations and their dependence on mixture composition and laser irradiation intensity were measured. A qualitative model is proposed to account for this periodic behavior. Allowance for temperature oscillations must be made in developing thermochemical or kinetic parameters from laser-powered homogeneous pyrolysis experiments.