Boltzmann equation analysis of electron-molecule collision cross sections in water vapor and ammonia

Abstract

Sets of electron-molecule collision cross sections for H2O and NH3 have been determined from a classical technique of electron swarm parameter unfolding. This deconvolution method is based on a simplex algorithm using a powerful multiterm Boltzmann equation analysis established in the framework of the classical hydrodynamic approximation. It is well adapted for the simulation of the different classes of swarm experiments (i.e., time resolved, time of flight, and steady state experiments). The sets of collision cross sections that exist in the literature are reviewed and analyzed. Fitted sets of cross sections are determined for H2O and NH3 which exhibit features characteristic of polar molecules such as high rotational excitation collision cross sections. The hydrodynamic swarm parameters (i.e., drift velocity, longitudinal and transverse diffusion coefficients, ionization and attachment coefficients) calculated from the fitted sets are in excellent agreement with the measured ones. These sets are finally used to calculate the transport and reaction coefficients needed for discharge modeling in two cases of typical gas mixtures for which experimental swarm data are very sparse or nonexistent (i.e., flue gas mixtures and gas mixtures for rf plasma surface treatment).

Transport coefficients and cross sections for electrons in water vapour: Comparison of cross section sets using an improved Boltzmann equation solution

“…Clearly, the results of Figure 5 indicate some limitations in the vibrational crosssection data from Ref. 25 and thus with the recommended vibrational cross sections of Itikawa and Mason. 11 The new and more detailed transport data of de Urquiqo et al, 24 in this region provide useful information for assessing the accuracy and completeness of the vibrational cross section sets.…”

“…1, but taking advantage of modern computing power to calculate transport coefficients to a considerably higher degree of accuracy than was previously possible. This allows a correspondingly more discriminating test of the various electron-water vapour cross section sets proposed, 1,2,11,[24][25][26] by establishing which among them furnishes the transport coefficients agreeing best with those from swarm experiments.…”

Non Thermal Plasma Sources of Production of Active Species for Biomedical Uses: Analyses, Optimization and Prospect

“…EEDF is obviously solution of Boltzmann equation of weakly ionized gas. The method recommended here to solve Boltzmann equation for the calculation of EEDF and then for electron transport and reaction coefficients has been described elsewhere (Yousfi 1996). It is based on the multi-term development of the distribution function (see in Fig.…”

“…The procedure of validation of every set of the electronmolecule collision cross sections (Yousfi et al 1996) is based on the known swarm unfolding technique summarized in the flowchart of fig 10. Figure 11 shows the adjustment done in the specific case of electron-H 2 O set on the ionization cross section to better fit the recent measurements of the effective ionization coefficients based on time resolved Townsend experiment (de Urquijo et al 2007).…”

“…Figure 11 shows the adjustment done in the specific case of electron-H 2 O set on the ionization cross section to better fit the recent measurements of the effective ionization coefficients based on time resolved Townsend experiment (de Urquijo et al 2007). (Yousfi 1996) www.intechopen.com …”