Nonequilibrium Radiation and the Recombination Rate of Shock-Heated Nitrogen

Abstract

The radiation emitted by hot nitrogen behind normal shocks is studied at an equilibrium temperature from 6000° to 6800°K and densities from 0.01 to 0.20 atm. The various radiating bands are identified by spectroscopic and photometric techniques. The radiation is found to consist of bands from the N2+(1−), N2(1+), and N2(2+) systems. The radiative relaxation of the N2(1+) system in the nonequilibrium region is studied at various densities and shock speeds and is used to determine the recombination rate constants, kRN and kRN2 for the reactions N + N + N → N2 + N and N + N + N2 → N2 + N2, respectively. kRN is found to be 1.8 × 10−32 ± 0.6 cm6/sec at 6400°K and kRN2 to be at least 13 times smaller than kRN. Comparison is made between theoretical calculations based on these rates and observations. The integral nonequilibrium radiation and the time of occurrence of peak radiation behind the shock front are also examined.