IMAGING SPECTROSCOPY OF THE NONEQUILIBRIUM SHOCK FRONT RADIATION IN AIR

The nonequilibrium radiation of shock fronts in air is experimentally investigated by means of the imaging spectroscopy technique. Shock vel ocity ranges from 9.7 to 11.6 km/s and initial pressure from 13.3 to 4 1.6 Pa. The spectral diagnostic system consists of an imaging spectrog raph, a streak camera, a gated image-intensified CCD camera and a pers onal computer for data acquisition/processing. This spectral diagnosti c system is capable of simultaneous wavelength-, intensity- and time-r esolved spectroscopic measurements in the nanosecond order. The image processing of the streak images includes a combined smoothing/deconvol ution process in the time direction to diminish experimental noise eff ects and the temporal broadening due to the streak camera entrance sli t. Wavelength range is chosen to investigate the first negative band o f N-2(+). ''Large'' and ''slim'' streak image types are observed. In t he ''large'' streak images greater contribution from N-2(+)(1-)(1,0) b ehind the radiation peak is observed. Experimental data are compared w ith a streak image numerically simulated. The numerical simulation agr ees better with the ''slim'' streak image.