Modeling of nitrogen atom recombination on Pyrex: Influence of the vibrationally excited N-2 molecules on the loss probability of N

A numerical modeling of the surface recombination of nitrogen atoms on Pyre x is developed to account for the temperature dependence of the loss probab ility gamma on the temperature in the range 290-611.5 K. Nitrogen atom reco mbination is a first-order Langmuir-Hinshelwood mechanism at a temperature below 400 K where both the Langmuir-Hinshelwood and the Eley-Rideal mechani sms are taking place above. Calculated results are compared to experimental measurements obtained in an Ar-N-2 Lewis-Rayleigh afterglow. Satisfactory agreement is obtained. The activation energy of the recombination processes is close to 20 kJ/mol. The weak difference between the theory and the expe riment is due to the value of the model parameters and not to the influence of the vibrationally excited molecules, which is very weak. It is suggeste d that the rate constant for vibrational de-excitation of N-2(X,v) by an ad sorption-phonon mechanism is underestimated. The recombination rate of nitr ogen atom on the wall of a cylindrical Pyrex tube is described by [GRAPHICS] with k=<gamma(c)over bar>(N)/2R. The temperature dependence of gamma is pro vided and it is complex but a rough estimation of the rate constant is give n by k = 17.9 exp(-5900/RT), with T in the range 290-611.5 K. (C) 2000 Amer ican Institute of Physics. [S0021-8979(00)05710-8].