D) reaction for atmospheric entry modeling *

During entry into Earth atmosphere, the flow surrounding space craft becomes ionized leading to significant cation and free-electron production. Subsequently, electron impact excitation and dissociation form radiating excited state species that contribute to the heat load on the vehicle. While experimental data on total cross sections are available, few experiments address the need for accurate AI cross sections for metastable states at the high temperatures realized in atmospheric re-entry. In order to maintain desired safety margins during atmospheric entry of a space vehicle, chemical reaction models need to accurately account for this process.

For the present study, we have computed vibrationally resolved cross sections for the DR of NO⁺ and apply microscopic reversibility to obtain the AI cross sections and rate coefficients. The resonance widths for the e-scattering process are calculated by the R-matrix method. The MRCI adiabatic potential curves are transformed to a diabatic representation, which is used in time-dependent wave packet calculations to describe the nuclear motion of the dissociating cation upon collision with an electron. These calculations provide DR cross sections including recombination into the low energy metastable atomic states.The DR and AI rate coefficients are compared with experimental data.