Surface loss probability of atomic oxygen on silica under atmospheric-pressure CO₂

The surface loss probability γ O of atomic oxygen was measured for SiO 2 in atmospheric-pressure CO 2 and Ar/CO 2 (3.05%) mixture at 300 K. O atoms were produced via the photolysis of CO 2 using a 172 nm Xe 2 excimer lamp. After irradiation by Xe 2 lamp, the working gas flowed through a quartz tube, causing O atoms to be lost on its inner surface. By measuring the density of O atoms at the end of the tube for different tube lengths, we obtained the value of γ O on the inner surface of the tube. The measured value was 5.5 × 10 −4 ± 50%, which falls within the range of referred values of γ O (1 × 10 −5 to 1 × 10 −3 ) at 4 to 1300 Pa measured using low-pressure O 2 plasmas. Despite the 2 to 5 orders of magnitude pressure difference, no significant difference in γ O was obtained. The potential influence of the difference in background gas (CO 2 and O 2 ) on the value of γ O was also considered.