DETERMINATION OF THE ABSOLUTE PHOTOLYSIS RATE OF OZONE BY SUNLIGHT, O3+HV-]O(1D)+O2(1DELTA-G), AT GROUND-LEVEL

An actinometric technique was used to evaluate half-hourly averaged rate constants k(1D) for the formation of O(1D) atoms by ozone photolysis in natural daylight below 310 nm. Sealed quartz bulbs containing a few torr ozone in 2200 torr N2O were used for the measurements. Molecular nitrogen resulting from the reaction of O(1D) with the scavenger gas was determined by gas chromatography. The results were corrected for the finite optical density of ozone and for its photochemically induced decay in the actinometer during exposure. Measurements were taken between August 1977 and July 1978, at solar zenith angles of 32-75°, and ozone column densities of 280-400 Dobson k(1D) values between 7 × 10-7 and 2 × 10-5 s-1 were found under clear sky conditions. The results are shown to depend systematically on both the solar zenith angle and the ozone column density, in accordance with a model calculation. The spatially integrated and spectrally resolved light intensity at 306 nm correlates well with the diurnal variation of k(1D). The results are compared with literature data. © 1979.