H(2S) and O(1D, 3P) yields have been measured from photolysis of H2O, NH3, and CH4 at 1216 Å. From H2O, it is confirmed that the H2+O(1D) channel occurs with a yield of 0.1, but in addition there is a yield of 0.12 for the channel giving 2H(2S)+O(3P). The remaining process is H+OH production. For NH3, the NH+2H(2S) channel accounts for at least 90% of the dissociation. For CH4, combination of our data with earlier work on H2 and CH production at 1236 Å leads to the conclusion that the two major dissociative channels generate 1CH2+H2 and CH2+2H(2S), with comparable probabilities. CH and CH3 production is at most minor. The yields at 1216 Å for the three-fragment processes O+2H, NH+2H, and CH2+2H, exhibit a dependence on the available excess energy.

Although 248-nanometer radiation falls 0.12 electron volt short of the energy needed to dissociate O(2) large densities of ozone (O(3)) can be produced from unfocused 248-nanometer KrF excimer laser irradiation of pure O(2). The process is initiated in some undefined manner, possibly through weak two-photon O(2) dissociation, which results in a small amount of O(3) being generated. As soon as any O(3) is present, it strongly absorbs the 248-nanometer radiation and dissociates to vibrationally excited ground state O(2) (among other products), with a quantum yield of 0.1 to 0.15. During the laser pulse, a portion of these molecules absorb a photon and dissociate, which results in the production of three oxygen atoms for one O(3) molecule destroyed. Recombination then converts these atoms to O(3), and thus O(3) production in the system is autocatalytic. A deficiency exists in current models of O(3) photochemistry in the upper stratosphere and mesosphere, in that more O(3) iS found than can be explained. A detailed analysis of the system as it applies to the upper atmosphere is not yet possible, but with reasonable assumptions about O(2) vibrational distributions resulting from O(3) photodissociation and about relaxation rates of vibrationally excited O(2) a case can be made for the importance of incuding this mechanism in the models.

The NO({:l) emission (B 'IT->X'II) observed during photolysis of N.O at 1470 A is due to a cherniluminescent reaction between N('D) and N.O. Transient measurements of this emission are analyzed to give the rate coefficients for removal of N (. D) by several simple molecules. Photolysis at 1236 A also produces NO(B 'IT), and the decay curves can be analyzed to give the same rate coefficients as observed at 1470 A, although there is evidence that an additional NO(B 'IT) production mechanism is involved. Quench'ng coefficients are also tabulated for N. (A 32;) and 0 (1 S), two other species investigated by the same technique.