76th Annual Gaseous Electronics Conference
Volume 68, Number 9
Monday–Friday, October 9–13, 2023;
Michigan League, Ann Arbor, Michigan
Session DF1: Diagnostics III
8:00 AM–9:15 AM,
Friday, October 13, 2023
Room: Michigan League, Hussey
Chair: Katharina Stapelmann, North Carolina State University
Abstract: DF1.00001 : Associative Ionization Processes in Nonequilibrium Plasmas
8:00 AM–8:30 AM
Abstract
Presenter:
Igor V Adamovich
(Ohio State University)
Author:
Igor V Adamovich
(Ohio State University)
Associative ionization processes in molecular and atomic collisions are of critical importance for the understanding of the kinetics of low-temperature plasmas and nonequilibrium high-enthalpy flows. The ionization cross section is greatly enhanced by the vibrational and electronic excitation of the collision partners. Predicting the rates of the associative ionization and other electronically nonadiabatic processes in collisions of excited molecules and atoms requires quantitative insight into the collision dynamics. The progress in the predictive capability of the molecular energy transfer theory over the last few decades owes a great deal to the development of accurate potential energy surfaces and efficient computational techniques. On the other hand, approximate analytic models of vibrational and electronic energy transfer, which yield the closed-form expressions for the energy transfer cross sections, have also demonstrated their accuracy and utility. This is illustrated by the good agreement between the analytic models and the “exact” semiclassical trajectory calculations or quantum scattering calculations. One of the essential factors in the development of these models is the emphasis on the dominant features of the collision dynamics, such as the multi-state coupling, effect of molecular rotations, and interference between the incoming and ongoing wavepackets. The objective of this work is the development of a semiclassical analytic model of nonadiabatic energy transfer in atomic collisions, using the generalized Landau-Zener-Stückelberg theory. This theory has been applied to the collisions between two ground state O atoms, to predict the cross section of electronic excitation, O(3P) + O(3P) ⟶ O(3P) + O(1S). The results are compared with the exact quantum solution, exhibiting excellent agreement. The focus on the ongoing work is the extension of this approach to the associative ionization in collisions of metastable excited atoms, such as N(2P) + O(3P) ⟶ NO+ + e-, one of the dominant ionization processes behind hypersonic shock waves. This model is complementary to the quasiclassical trajectory calculations and can be used for the predictive simulations of nonequilibrium plasmas and hypersonic flows.