Chemical Relaxation in Cooling Air Plasmas

To study the relaxation of air plasmas from an initial to a final equilibrium state, a numerical code solving the system of time-dependent coupled rate equations for 13 chemical components including atomic and molecular oxygen negative ions has been developed. The equilibrium plasma compositions have been computed assuming conservation of initial numbers of nuclei (non-constant pressure). About 80 exothermic reactions were considered, the corresponding rate coefficients being taken from the literature. The preliminary results exhibit strong departures from the statistical Saha or Guldberg-Waage equilibria; each plasma component relaxes with a characteristic time.