Integrated Intensity Measurements of the 1.9-μ Bands of CO2 in the Temperature Range 1400° to 2500°K

Abstract

Measurements have been made of the total integrated band intensity of the 1.9-μ bands of CO2 in the temperature range 1400° to 2500°K. The gas was heated to the high temperature by a shock wave reflected from the rigid end plate of a shock tube. The experiment determines the total integrated band emission as a function of optical path length. The total emission is related to the integrated band intensity in a simple way. The intensity in the 1.9-μ region of the CO2 spectrum arises from three combination bands, namely the (v3+4v2), (v3+2v2+v1), and (v3+2v1) bands. These band systems are in strong Fermi resonance. The bands have not been resolved; the total integrated intensity of the three bands was measured as a function of temperature. The temperature dependence of the absolute intensity is discussed in terms of a simple model using the harmonic oscillator approximation to the CO2 molecule. The results indicate that the intensity in the 1.9-μ resonant triplet of CO2 originates in the (v3+2v1) band. An extrapolation of the data using the derived temperature dependence gives an integrated band intensity of 2.07 (cm—2 atm—1) at STP for the total 1.9-μ CO2 band.