Аннотация:It is well-known that negative ions play an important role in plasmas of electronegative gases. They affect a lot of processes. E.g. reactions of associative detachment on active particles (radicals, metastable atoms and molecules) cause changes in a charge composition, thereby directly influencing on the electric field distribution and EEDF. Furthermore, negative ions take an active part in various plasma-chemical reactions, such as plasma etching, polymerization and dusty particles formation. The dynamics of negative ions N^- in oxygen dc glow discharge in a wide range of pressure and current density of the discharge (P=0.16-2 Torr, I=5-25 mA/cm2) was investigated. The N^- concentration was measured by the laser photodetachment technique. As experimentally shown by using the discharge modulation, the N^- concentration varies with the characteristic times of evolution of oxygen atoms O(^3P) and metastable molecules O_2(a^1Δ _g). To investigate the dynamics of atomic oxygen density the actinometry technique was applied. The dynamics of O_2(a^1Δ _g) molecules was investigated by the IR spectroscopy at 1.27 μm. Moreover, the photodetachment technique was also applied for studying the spatial distribution of negative ion density. It has been shown that O^- ion is the main negative ion in low pressure plasma. The analysis of the data of O^- ion dynamics allowed to determine the rate constants of the associative detachment on O(^3P) atoms and O_2(a^1Δ _g) molecules in plasma for the first time: O^- + O(^3P) -> O2 + e; O^- + O_2(a^1Δ _g) -> products + e.