INFRARED INTEGRATED BAND INTENSITY MEASUREMENTS BEHIND REFLECTED SHOCK WAVES

Author Institution: General Dyamics/Astronautics, Space Science Laboratory“A shock wave technique is described which provides a means of measuring the infrared integrated intensity of molecular bands at elevated temperatures. The total bund emission from the high temperature gas region existing between the end plate of a shock tube and the reflected shock wave was measured using a rapid response infrared detector. The emission is obtained as a function of path length as the reflected shook wave recedes from the end plate. The initial concentration, shock velocity and reflected shuck pressure were measured and the final conditions of the test gas were calculated from the normal shock relations. An absolute intensity calibration of the detector and monochromator system was obtained using a standard blackbody source. The absolute band intensity is obtained from the slope of a plot of total emissivity versus optical path length. The method has been used to measure the absolute intensity of the 2.7 micron combination band of $CO_{2}$ in the temperature region $1000^{\circ} K$ to $3000^{\circ} K$. To insure adequate pressure broadening for this weak band and yet to remain within the optically thin linear region, the measurements were made at 2.5 atms total pressure and 0.1 atm $CO_{2}$ partial pressure.