Pi Sensitized Formation of Ozone

Ozone synthesis by mercury (3Pf) photosensitization was first reported by Dickinson and Sherrill (24). They reported that at least 7 molecules of ozone are formed for each mercury atom passing through the reaction zone. Subsequently, Volman (91) found that at least 40 molecules of ozone could be formed for each mercury atom and still later reported a value of 60, (92). The above studies were made in flowing systems at atmospheric pressure. Callear et al. (18) have investigated the reaction by photometeric and thermal methods in a static system at pressures of 200 mm. or less. A quantum yield of 0.14 was reported, and evidence that oxygen was not removed by reaction with Hg(3P1) atoms and that mercury was removed by a dark reaction with ozone was obtained. In all of the above studies mercuric oxide was always formed. 

The value of X is not known but has been estimated at not over 23 kcal. 

Of the above reactions, only (15) is consistent with the experimental observations. Calculations from collision theory based on the endother-micity of reaction (13) indicate that only one collision in about 104 could yield oxygen atoms. Since the quantum yield of ozone formation has been estimated at 0.03 (91) and as high as 0.14 (18), and since long chains are not possible, this reaction cannot be important. In reaction (14) one mercury atom is removed for each oxygen atom formed. Since 60 or more ozone molecules may be formed for each mercury atom removed, this reaction cannot be important unless mercury is regenerated. The postulated reaction (61) 

The effects of foreign gases (92) on the reaction were studied in the same manner as for the unsensitized reaction discussed in Part II. In a 20-mm. diameter cylindrical quartz reaction vessel at a flow rate of 2.0 1/min. at 1-atm. total pressure and 0.25-atm. oxygen pressure, the relative rates of ozone formation were  

Oxygen Slates by Energy Transfer from. Mercury (3Pi) 

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