Optical actinometry of O-atoms in pulsed nanosecond capillary discharge: Peculiarities of kinetics at high specific deposited energy

The density of O-atoms was studied in a nanosecond capillary discharge in air with 5.3% additions of Ar at 28.5 mbar. Time-resolved electrical current, longitudinal electric field, optical emission of O(3p³P) at λ _O = 844.6 nm, Ar(2p₁) λ _Ar = 750.4 nm and their ratio, and emission of N₂(C³Π_u) at were measured. A kinetic scheme describing consistent behavior of the set of the experimental data was developed. The main processes responsible for population and decay of the species of interest were selected on the basis of sensitivity and rate analysis. The electric field was taken as input data; all other experimentally obtained signals were modeled; experimental data and results of calculations were in good agreement. The role of the reactions between excited, charged species and electrons in the early afterglow for pulsed discharges at high reduced electric fields and high specific deposited energy was discussed. The density of O-atoms in the ground state was calculated. It was concluded that Ar-based traditional actinometry demands advanced kinetic modeling with regards to the nanosecond discharge with a high specific energy deposition and high reduced electric field.