Calculation of the Effective Ionization Rate in Air by Considering Electron Detachment From Negative Ions

Abstract

Abstract-The effective Townsend ionization coefficient in dry air at different pressures and temperatures is calculated taking into account ionization by direct electron impact, attachment of electrons to molecular oxygen, simplified negative ion kinetics and detachment of electrons from negative ions in collisions with heavy neutrals. Effect of electron detachment from negative ions created by primary and secondary electron avalanches propagating in a uniform electric field in air at different pressures and temperatures, and its contribution into the effective ionization rate are analyzed.

On the Problem of Critical Electric Field of Atmospheric Air

“…It follows from Figure2that the field E c , whose calculation involves a wide set of plasma-chemical reactions (see Appendix A), is significantly smaller than the conventional field E b , the concept of which assumes that only ionization and attachment processes are significant. This is because, in agreement with previous studies[2,[4][5][6][7], the role of electrons' detachment from negative ions cannot be neglected. Conversions between different types of negative ions are also important because each detachment reaction involves a specific sort of negative ions.…”

“…As in previous studies (for example, [2,[4][5][6][7]), the sought critical electric field E c is defined as a field at which the first positive eigenvalue λ + of the matrix A, which can also be called an effective ionization frequency ν eff , appears. It should be noted that some components of the evolution matrix A are sharp functions of both reduced electric field E/N and air temperature T. The components of the eigenvector x + corresponding to the eigenvalue λ + , which characterize ion composition of atmospheric air, also depend on electric field and altitude AMSL.…”

“…There are numerous studies (see [2,[4][5][6][7] and references therein) discussing the influence of electron detachment from negative ions on the critical breakdown field of air. In [4], two additional (with respect to impact ionization and attachment) plasma-chemical processes were employed: detachment of electrons from O − 2 ions…”

“…Similarly to [4], it was shown that the resultant system of four differential equations that involves the number densities of electrons and O − , O − 2 , O − 3 , N + 2 , and O + 2 ions loses stability when ν i < ν a . This result was later refined in [5] with additional consideration of reactions ( 6) and ( 8) along with the following detachment processes involving O atoms:…”

Tuning Surface Wettability through Hot Carrier Initiated Impact Ionization in Cold Plasma

“…HCP does not release thermal radiation that can damage cell membranes, and UV–vis radiation that primarily governs the excitation and relaxation of nitrogen molecules is not considered to dominate the surface modification mechanism and the eradication of microorganisms because of their low energies and ultrathin penetration depths. ,, Conversely, UV and the E-field induced in the HCP play supplementary roles in enhancing the generation of RONS; UV radiation-induced photochemical transformations increase the generation of these species. ,,, Similarly, E-field stress does not directly modify the surface but rather supports the generation of other plasma compounds via impact ionization. We employed the principle of hot electron-initiated impact ionization in an insulator under high E-field , to explain the exponential behavior of WI (time) as a function of NAP treatment time (Figure b) through the equation where WI (max) is approximately the WI (time) of the untreated seed, k is an empirical plasma constant that reflects the number of free radicals generated and depends on the NAP setup and seed conditions. In this work, k is ∼10 and ∼5 at electrode separations of ∼5 and ∼7 cm, respectively.…”