The quantum yield of O(1D), &PHgr;(T), in the 308 nm photolysis of ozone has been shown to decrease very slightly with temperature (T), from 0.79¿0.10 at 298 K to 0.73¿0.10 at 200 K. At 248 nm, &PHgr; is (0.91¿0.06) independent of temperature (200--320 K). The rate constant for the reaction of O(1D) with O3 was measured to be (2.3¿0.5)¿10-10 cm3 molecule-1 s-1, independent of temperature (200--350 K). The measured quantum yields suggest that the current recommendations over-estimate the effect of temperature on O(1D) quantum yields in O3 photolysis at 308 nm.¿ 1997 American Geophysical Union