Volume and surface loss of O( 3 P) atoms in O 2 RF discharge in quartz tube at intermediate pressures (10 - 100 Torr).

O(alt;supagt;3alt;/supagt;P) atom loss has been studied in Oalt;subagt;2alt;/subagt; RF plasma in the quartz tube in the intermediate pressure range (10-100Torr) when transition from the surface to volume loss is observed. Space- and time-resolved actinometry on Ar and Kr atoms was used to study O(alt;supagt;3alt;/supagt;P) atom loss. The research showed that such transition actually takes place. It was revealed that the gas temperature plays significant role at this. Gas temperature was measured spectroscopically using Oalt;subagt;2alt;/subagt;(balt;supagt;1alt;/supagt;Σalt;subagt;galt;/subagt;alt;supagt;+alt;/supagt;,v=0)→Oalt;subagt;2alt;/subagt;(Xalt;supagt;3alt;/supagt;Σalt;subagt;galt;/subagt;alt;supagt;-alt;/supagt;,v=0) band emission. It was demonstrated that the gas temperature in the plasma volume was rather high (agt;1200K) due to the high values of the specific input RF power which in turn led to significant O(alt;supagt;3alt;/supagt;P) loss rate decrease in the discharge volume. The atomic oxygen loss is limited by the O(alt;supagt;3alt;/supagt;P) surface recombination as well as by the volume recombination in a thin layer near the wall. It leads to low integral loss rate and provides high oxygen dissociation degree. Analysis based on measured [O(alt;supagt;3alt;/supagt;P)]/N, Talt;subagt;gasalt;/subagt;, Oalt;subagt;3alt;/subagt; spatial profiles and surface loss model including recombination with chemi- and physisorbed atoms has revealed the importance of both surface and volume losses. High values of the specific input RF power also lead to increase of the gas temperature near the wall and the temperature of the internal tube surface. As a result, the O atom surface loss rate increases and the volume loss rate near the wall decreases. In the whole the contributions of both O(alt;supagt;3alt;/supagt;P) volume and surface recombination are comparable at pressures up to 100Torr. The O(alt;supagt;3alt;/supagt;P) loss kinetics at intermediate pressures appears to be rather complex phenomenon and requires at least 1D modelling for its correct description. Global models under the similar conditions may lead to doubtful results in detailed study of kinetic mechanisms but can be useful for simple analysis of experimental results.