Vibrational Energy Transfer in Shock-Heated N2–HI and N2–DI Mixtures

Abstract

The vibrational relaxation of N2–HI mixtures in the temperature range 1000–2700°K and of N2–DI mixtures in the range 1200–2000°K has been studied behind incident shock waves by time-resolved measurement of the postshock density gradient using a laser-beam deflection technique. In both systems the vibrational relaxation of N2 is dominated by vibration–vibration (V–V) energy transfer from the halide gas; contributions due to translation–vibration (T–V) and/or rotation–vibration (R–V) energy transfer are negligible. V–V energy transfer is more efficient in N2–HI than in N2–DI collisions, but the difference is much less than predicted by the SSH theory. Results for the effect of N2 on the relaxation of HI and DI support previous suggestions that R–V energy transfer is the dominant mechanism for vibrational relaxation of the hydrogen halides.