ИСТИНА

The experiments on studying dynamics of negative ions by laser photodetachment were carried out at the same discharge parameters and experimental conditions as during the time-resolved CRDS measurements in DC pulsed discharge. The following modulation was used: 0.2s – discharge is on, 0.8s – afterglow (discharge is off). Identical discharge tubes were used in LPP and MSU. In MSU the O- and O2- ions dynamics was measured by laser photodetachment using two lasers, at 532 nm and 1064 nm. The O2(a) molecules dynamics was measured by IR OES. In LPP the O(3P) atoms density dynamics was measured by on-resonance O(3P2)->O(1D2) absorption at 630 nm by the time-resolved CRDS while O- density dynamics was detected by off-resonance absorption. The current and electric field dynamics and actinometric ratio IO/IAr were also measured to compare the surface conditions of the tubes. Wall temperature of +50C was fixed by external thermostatic chiller. Gas pressure range from 0.2 to 2 Torr and discharge current range from 10 to 40 mA was studied. The O- and O2- dynamics is determined by fast detachment reactions with O(3P) atoms and O2(a) molecules. Wall loss probabilities for O(3P) atoms and O2(a) molecules were obtained by describing experimentally measured dynamics of corresponding species. Experiments were analysed using a self-consistent one-dimensional 1D model of a pulsed dc glow discharge in a tube. Example of the calculated curves and experimental data on the dynamics of the O atoms and O2(a) mole fractions at pressure of 1.5 Torr is shown in Fig. 1. Fig. 2 shows the O2-/O- density ratio dynamics. Comparison of model curves with experimental data for O2-/O- made it possible to evaluate the rate constant of the quasi-resonant charge exchange reaction O-+ O2(a)->O2-+O.