Non-equilibrium coupled kinetics in stationary N₂-O₂discharges

Abstract

A detailed study of the coupled electron and heavy-particle kinetics in a low-pressure stationary N2-02 discharge is carried out. The model i s based on the self-consistent solutions to the Boltzmann equation coupled to the rate balance equations for the vibrationally excited molecules N2(X 'E;, v) and 02(X ' E ;. v'), NO(X 211r) molecules and N(4S) and O('P) atoms. It is shown that the vibrational distribution of N2@, v) plays a central role in the whole problem, affecting considerably the predicted concentrations of NO molecules and N atoms, whereas the concentration of 0 atoms is practically independent of both vibrational distributions. In particular, it is shown that, in the case of a rate coefficient of about cm3 s-I for the reaction N2@. v) + 0-+ NO + N. the Nz(X, v) molecules are strongly de-excited by vibrational-translational energy exchange processes associated with N 2-N collisions. In contrast, in the case of a higher value for this rate coefficient, the N2(X, v) molecules are efficiently destroyed by this mechanism. The contributions of the different processes to the total production of NO. N and 0 are evaluated and compared.

State-Resolved Dissociation Rates for Extremely Nonequilibrium Atmospheric Entries

“…This theory is capable to simulate single-jump transition probabilities in conditions where these are much smaller than unity. This is the case for the simulation of state-to-state processes in gas discharges where this theory can be successfully applied [21].…”

“…At lower temperatures (T < 25; 000 K), a sharp increase in the dissociated fractions is observed, which indicates the existence of a ladder-climbing phenomenon only noticeable at lower temperatures. This is typically the phenomenon that contributes for dissociation in other lowertemperature applications such as gas discharges [21], where only single-quantum transitions are considered. Also the determinant influence of the shock temperature on the delay after which the flow is completely dissociated is clearly seen.…”

Direct molecular simulation of high-temperature nitrogen dissociation due to both N-N2 and N2-N2 collisions

“…Collisions between diatomic nitrogen molecules involve translational, rotational, and vibrational energy transfer mechanisms that populate upper rovibratinal energy levels, 3,4 ultimately leading to dissociation. Thus, excitation and dissociation resulting from N 2 -N 2 collisions are precursors to N-N 2 collisions and the formation of NO 4 in air, as well as electronically excited species.…”

Role of nitrogen in the downstream etching of silicon nitride

“…Additionally, the probability of significant and measurable amounts of N in the reaction chamber is low because the reaction of N with O 2 , NϩO 2 → NOϩO, is an important mechanism for both NO production and N loss in discharges with a predominance of O 2 . 8 The N atoms also react very rapidly with NO by the reaction NϩNO → N 2 ϩO. The absence of NO ␤-or ␥-band emission in the etch reaction chamber under these same conditions supports the conclusion that N atoms are unlikely to be important.…”

“…That NO 2 and N 2 O also enhance the etch rate when injected downstream, but not to the same extent as NO, is a consequence of their ability to react with O atoms to form NO. Since the enthalpy of reaction for N 2 ϩO→NOϩN is ⌬H 0 ϭϩ75 kcal/mol, N 2 can react with O to form NO when injected into the discharge, 8 but there is no excitation source for N 2 to participate in the formation of NO downstream.…”