Fast gas heating and radial distribution of active species in nanosecond capillary discharge in pure nitrogen and N₂:O₂ mixtures

Fast gas heating is studied experimentally and numerically using pulsed nanosecond capillary discharge in pure nitrogen and N₂:O₂ mixtures under the conditions of high specific deposited energy (up to 1 eV/molecule) and high reduced electric fields (100-300 Td). Deposited energy, electric field and gas temperature are measured as functions of time. The radial distribution of active species is analyzed experimentally. The roles of processes involving N₂(B) = N₂(B³ Πg, W³ Δu, B′³ ς_u), N₂(A³ ς⁺_u) and N(²D) excited nitrogen species leading to heat release are analyzed using numerical modeling in the framework of 1D axial approximation.