The method of chemical difference was utilized to accurately deterornine the relative importanceoof all the reaction steps in the direct photolysis of NzO at 21 39 A (25" and 250°C) and 1849 A (25" C), as well as in the Hg6('Pl)-sensitized photolysis of Nz0 at 1849 A (25°C). (1) NzO + hv or Hg6('PI) + Nz + O(lD) Experiments with trace amounts of C & l 6 added showed a slight, but not significant, difference in product ratios (Nz and 0 2 ) . From these experiments the quantum yield of O(3P) fromoall possible sources was estimated as 0.02 f 0.02. Experiments with excess NP at 1849 A indicated that O(lS) was not produced in the direct photolysis. The O(*S) yield is probably zero, and certainly <0.05. The O(lD) atom can react with NzO via
(3)
In all cases, the primary process is predominantly, if not exclusively,
The ratio kZ/k3 was found to be 0.69 f 0.05 in all cases. When combined with other data from our laboratory, the average value is 0.65 f 0.07. This represents the value for translationally energetic O(lD) atoms. When excess He was added to remove the excess translational ehergy, kz/k3 rose to 0.83 f 0.06, which is in reasonable agreement with the value of 1.01 f 0.06 found in another laboratory. We conclude that for O(lD) atoms with no excess thermal energy, k 2 / k 3 = 0.90 f 0.10.