SPECTROGRAPHIC INVESTIGATION OF THE STATE OF A GAS BEHIND A SHOCKWAVE. PART I

A series of systematic experiments were carried out to determine the air temperatare behind a shock wave according to the relative intensity of non- resonance Na and Li lines for wave velocities of 3 to 4 km/sec. Sodium and lithium were introduced into a shock tube in the form of NaCl and LiCl. It was established that the large scatter in the experimental results depended on reabsorption whose degree varied from experiment to experiment. The considerable concentrations of dyestuffs in the air, which was required to produce measurable line intensities, lead to reduced values of the temperature in comparison with the theoretical values. An added reason is the inhomegeneons cross-sectional distribution of the coloring material. It appears to be concertrated near the cold wall of the shock-tube. In order to eliminate this inhomogeneity effect in a subsequent series of experiments, dicyanogen was added to the air and ihe temperature was determined according to the relative intensity of the vibrational bands of cyanogen with unresolved rotational structure. A large series of experiments showed that different pairs of bands lead to significatnly different temperatures. The scatter being observed cannot be explained by jsut the reabsorption but is apparently also related to themore » lag in the equilibrium build- up in the vibrational degrees of freedom of the cyanogen. (auth)« less