Mass independent fractionation Research Papers (original) (raw)
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Stratospheric ozone is enriched in the heavy isotopes (17O and 18O) relative to the ambient oxygen from which it is formed. This enrichment varies with altitude, attaining very high values between 30 and 40 km. A recent theory of Y. Q.... more
Stratospheric ozone is enriched in the heavy isotopes (17O and 18O) relative to the ambient oxygen from which it is formed. This enrichment varies with altitude, attaining very high values between 30 and 40 km. A recent theory of Y. Q. Gao and R. A. Marcus explores the reasons for isotopic enrichment in the process of ozone formation and is particularly useful to understand the laboratory results. The stratospheric variations are sought to be explained in terms of temperature dependence of isotopic enrichment, but the magnitude of variation does not match with predictions accurately. We demonstrate here that isotopic enrichment in ozone generated by oxygen photolysis depends on the pressure of the oxygen reservoir and can have very high values (at about 15 torr), comparable to the highest observed stratospheric values. Analysis of the data shows that secondary enrichment through ozone dissociation can add to the primary enrichment associated with ozone formation. The effect of disso...
The products of ozone dissociation occurring on glass surface are enriched in heavy oxygen isotopes ( and ) in a mass independent () fashion. Such behavior is in contrast to the case of thermal dissociation where fractionation is mass... more
The products of ozone dissociation occurring on glass surface are enriched in heavy oxygen isotopes ( and ) in a mass independent () fashion. Such behavior is in contrast to the case of thermal dissociation where fractionation is mass dependent (). Even photo-dissociation by visible light is a mass dependent process. The mass independent fractionation in surface dissociation can probably be explained by assuming that the dissociation takes place via a short-lived complex involving the ozone molecule and an active surface site. The anomalous isotopic fractionation in surface dissociation can be useful to decipher the mechanism of surface reaction in some cases.