Laser-induced fluorescence of oxygen atoms in a plasma reactor

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Abstract
Two-photon laser-induced fluorescence (LIF) of ground-state oxygen atoms following excitation of the 2p3 3p1 3P–2p4 3P transition has been investigated in a rf parallel-plate plasma reactor. Stimulated emission on the 2p3 3p1 3P–2p3 3s1 3S transition is readily detected, and leads to marked nonlinearities in the LIF signal as a function of O-atom concentration. Absolute concentrations have been determined as a function of gas composition in CF4/O2 mixtures, and shown to depend on the measured wall loss rates. The method is used to indicate limitations in the use of optical emission as a diagnostic for O atoms.