1 Experimental Investigations of Rovibrational Temperatures Derived from Different Electronic state

To investigate the influence of electronic state on the relaxation process of nitrogen molecule behind a shock wave, spectroscopic measurement is conducted using a free-piston double diaphragm shock tube. The shock velocity and the spectrum position from the shock front are determined by the double laser schliren measurement system which is newly developed for precise measurement. Emission spectra of N2(1+) and N2(2+) are obtained by means of the time resolved imaging spectroscopy. Rovibrational temperatures are derived from N2(1+) and N2(2+) and finally temperatures distributions correlated to the shock front are obtained. The measured rotational temperature of N2(1+) is higher than that of N2(2+). The rotational relaxation of N2(2+) looks slower than that of N2(1+). However, the measured vibrational temperatures of N2(1+) and N2(2+) are close to each other and agree well with the prediction of the two-temperature model. Nomenclature L = distance from the shock front, mm L1 = distance between laser beams, mm L2 = distance between upstream laser and measurement position, mm d1 = time difference of the schliren signals, µs d2 = time difference of the upstream schliren signal and the gated signal, µs d3 = passing time of shock wave between upstream laser and measurement point, µs P0 = ambient pressure ahead of the shock wave, Pa Tt = translational temperature, K Tr = rotational temperature, K Tv = vibrational temperature, K V = incident shock velocity, K I