Mass-Dependent Isotopic Fractionation in Ozone Produced by Electrolysis
Résumé
During the electrolysis of water in an acidified medium, ozone is produced, in association with oxygen, at the anode. This ozone is found to be depleted in heavy isotopes (18O and 17O), with respect to the source water, following a strict mass-dependent rule. Our experiments also suggest that the isotopes are distributed at the apex and base positions of the bent ozone molecule in a random fashion, without obeying the zero-point energy constraint. Endowed with these characteristics, the electrolytic ozone provides a source of reference that has a known internal heavy isotope distribution for spectroscopic studies. In addition, this ozone, when subjected to photolytic decomposition, can be used as a source of atomic oxygen with mass-dependent isotope ratios that can be varied by simply changing the water composition. Such an oxygen source is important for studying isotope effects in gas-phase recombination/exchange reactions such as COO + O* → [COOO*] → COO* + O.