Time‐resolved resonance fluorescence studies of O(1D2) yields in the photodissociation of O3 at 248 and 308 nm

Study of the Formation Dynamics of OH from the Photolysis of O3 by Ultrashort Laser Pulses

We report the first experimental detection of the laser-induced formation dynamics of OH under normal pressure, which was observed using the pump-probe scheme with two 250 fs laser pulses at 282.2 nm. The first laser photolyzes O₃ to form OH, and the second laser excites OH to induce fluorescence at 308 nm. The fluorescence cannot be detected with a single beam because the femtosecond pulses have already passed through the sample before the formation of OH from their own photolysis. A photochemical dynamic model was built, and the experimental results are in good agreement with the model. This method can also be used for other OH-related dynamic measurements, which can effectively avoid laser-generated interference from the photolysis of O₃.

The "Ozone Deficit" Problem: O2(X, v ge 26) + O(3P) from 226-nm Ozone Photodissociation

Highly vibrationally excited O(2)(X(3)sigmag(-), v >/= 26) has been observed from the photodissociation of ozone (O(3)), and the quantum yield for this reaction has been determined for excitation at 226 nanometers. This observation may help to address the "ozone deficit" problem, or why the previously predicted stratospheric O(3) concentration is less than that observed. Recent kinetic studies have suggested that O(2)(X(3)sigmag(-), v >/= 26) can react rapidly with O(2) to form O(3) + O and have led to speculation that, if produced in the photodissociation of O(3), this species might be involved in resolving the discrepancy. The sequence O(3) + hv --> O(2)(X(3)sigmag(-), v >/= 26) + O; O(2)(X(3)sigmag(-), v >/= 26) + O(2) --> O(3) + O (where hv is a photon) would be an autocatalytic mechanism for production of odd oxygen. A two-dimensional atmospheric model has been used to evaluate the importance of this new mechanism. The new mechanism can completely account for the tropical O(3) deficit at an altitude of 43 kilometers, but it does not completely account for the deficit at higher altitudes. The mechanism also provides for isotopic fractionation and may contribute to an explanation for the anomalously high concentration of heavy O(3) in the stratosphere.