Study of oxygen atom recombination on a Pyrex surface at different wall temperatures by means of time-resolved actinometry in a double pulse discharge technique

The surface recombination probability of oxygen atoms as a function of wall temperature is studied by using a double pulse discharge technique. The main discharge pulse dissociates molecular oxygen and the second pulse, shorter than the main one, excites atoms during the stationary afterglow. The recombination probability is determined from the atomic oxygen density decay during the stationary afterglow of the main pulse (MP). The oxygen atoms are detected by time-resolved optical emission spectroscopy. In order to correlate the oxygen emission lines with the oxygen atom density, argon is used as an actinometer. To scan the whole afterglow of the main discharge pulse, the delay of the probe pulse is uniformly increased in every period following the MP. The evolution of the relative O atom density is deduced from the O emission lines at 777 and 844 nm and from the Ar actinometry line at 750 nm. The wall recombination probability γ on a Pyrex surface ranges from 4.0 × 10 −4 to 1.6 × 10 −2 for wall temperatures from 77 to 460 K.