Detection of atomic oxygen: Improvement of actinometry and comparison with laser spectroscopy

The density of atomic oxygen in an oxygen rf discharge in the Gaseous Electronics Conference reference cell is determined from the intensity ratios of the argon λ=750 nm line (2p1–1s2) and the atomic oxygen lines λ=777 nm (5P–5S) and λ=844 nm (3P–3S). Laser induced fluorescence spectroscopy with two-photon excitation is applied to the oxygen plasma, and the results of both methods are compared. The improved actinometry is based on the calculation of electronic collisional excitation of the upper levels of these transitions. The required information on the electron energy distribution function is obtained from a model calculation of the discharge. Good agreement of the results are obtained, if excitations via dissociative channels and also quenching rates are accounted for.