RADIATIVE ENERGY TRANSFER ON ENTRY INTO MARS AND VENUSQUARTERLY REPORT NO. 4

The emissivity of carbon dioxide in the 2.7 4 µ region has been measured at temperatures from 2000°K to 3500°K, for optical densities less than 5 atm-cm. The high temperatures were obtained by passing a shock wave through the test gas. A total gas pressure of one atm was maintained by varying the carbon dioxide concentration in an inert gas. Emissivities obtained from absorption and emission measurements are in agreement. results are compared to an approximate method for calculating emissivity, The which considers the molecular population concentrated in a single band whose center is temperature dependent. A comparison with previous results suggests that this single band model will overestimate the peak and underestimate the width of the observed values. The observed and calculated emissivities are in agreement if the intensities of the (n1 +1,n2, n3 + 1 → n1, n2, n3) and (n1,n2 +2, n3 + 1 → n1, n2, n3) transitions are assumed proportional to (n1 +1) (n3 +1) and (n2 +1)(n3 +1)/2. The use of this single band model which was originally intended to provide a rough prediction of emissivity, indicates that the use of the appropriate terms of the electric dipole expansion is satisfactory for the (n1 +1,n2, n3 + 1 → n1, n2, n3) transition, but is not for (n1,n2 +2, n3 + 1 → n1, n2, n3) transition.