Temperature dependence of O(1 D) formation in the near U.V. photolysis of ozone

Abstract

A chemiluminescence technique has been used to determine O(¹D) quantum yields from the near u.v. photolysis of ozone as a function of wavelength between 295–320 nm. Measurements at the four temperatures 230, 263, 298, and 320 K indicate a shift of the O(¹D) quantum yield curve towards shorter wavelengths as the temperature is reduced. The apparent discrepancies between our previous data at 298 K and those of Lin and DeMore at 235 K are thereby reduced. Comparison of the experimental results with model calculations assuming rotational excitation of ground state ozone to be responsible for the temperature effect indicate that thermal excitation alone is insufficient to explain the experimental results. An additional dependence exists for the O(¹D) production efficiency at energies above the dissociation limit which we tentatively ascribe to predissociation and to the influence of rotational levels on this process.