Knowledge Bank

Relative cross sections of the Hartley-Huggins bands of $O3$ at 195 K have been obtained based on Hearn's values at several Hg-lines. Photoabsorption measurements have been carried out with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 line $mm-1$ grating and operated at an instrumental width (FWHM) of 0.003 nm. Fine structures in the cross section in the Huggins band are observed with shallow features of width 0.01-0.02 nm superposed on stronger broad bands, Absolute cross sections at 298 K, 228 K and 195 K have also been measured at 13 different wavelength points including the 5 ultraviolet Hg-line wavelengths used by Hearn. This work is supported by the NASA Upper Atmospheric Research Program under Grant NAG 5-144 to Harvard College.