THE OZONE DEFICIT PROBLEM - O-2(X,V-GREATER-THAN-OR-EQUAL-TO-26)+O(P-3) FROM 226-NM OZONE PHOTODISSOCIATION

Highly vibrationally excited O-2(X(3) Sigma(g)(-), v greater than or equal to 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) Sigma(g)(-), v greater than or equal to 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 + h nu --> O-2(X(3) Sigma(g)(-), v greater than or equal to 26) + O; O-2(X(3) Sigma(g)(-), v greater than or equal to 26) + O-2 --> O-3 + O (where h nu 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.