Collisional deactivation of N₂(C³P_u) and N₂⁺(B²S⁺_u) by hydrocarbon molecules in afterglow of the picosecond discharge

In this paper the dynamics of the nitrogen electronic state relaxation is investigated by the emission spectroscopy of high time resolution in afterglow of the picosecond pulse repetitive high-voltage discharge in the form of fast ionization wave (FIW). FIW was initiated by negative polarity voltage impulses of 150 kV amplitude. The pulses have 250 ps duration at half amplitude, 100 ps rise time and 10 Hz repetition frequency. The pulses were delivered from a high-voltage pulser to the high-voltage electrode of the discharge cell through a coaxial cable with an impedance of 50 Ohm. The measurements were performed for 0-0 transitions of the second positive system of nitrogen (337.1 nm) and the first negative nitrogen system (391.4 nm). At the stage of earlier afterglow prior to 100 ns the electronic excited state relaxation in N₂–M mixtures takes place due to collisional deactivation and radiative depopulation. The collisional quenching rates were obtained for a wide range of hydrocarbons.