Ionization Rate of Air behind High-Speed Shock Waves

Measurements have been made of the ionization rate of air behind strong shock waves for shock velocities between 9 and 12.5 mm/μsec. The electron density behind the shock was determined from the infrared emission around 6 μ, this radiation being predominantly free-free bremsstrahlung. It was concluded that at shock speeds below 9.5 mm/μsec the predominant ionization mechanism is the reaction, N + O → NO+ + e, as postulated by Lin and Teare for slower shock speeds. However, for shock speeds above 9.5 mm/μsec, electron impact becomes the predominant ionization mechanism.