Kinetic study of a N₂-CH₄ afterglow plasma for production of N-containing hydrocarbon species of Titan’s atmosphere

Abstract

We present the results from a self-consistent kinetic model simulating the afterglow of a flowing microwave discharge in pure N ₂ in which CH ₄ is introduced in the post-discharge. The simulation is carried out for a discharge operating at 433 MHz, in a tube of 1.9 cm inner radius, at the pressure range 26.6-133 Pa. In the post-discharge the CH ₄ is primarily dissociated into CH ₃ and CH ₂ due to collisions with the metastables N(AΣu+) and N(a1Σu-) coming from the discharge, while HCN is obtained from collisions of CH ₃ and CH ₂ with N( ⁴S) atoms. Our calculations show that numerous species existing in Titan's atmosphere are then formed as a result of a complex interplay kinetics. The time-evolution of the species is investigated along the afterglow as well as the possibility of these species being precursors to the formation of organic aerosols.