München 2004 – wissenschaftliches Programm
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UP: Umweltphysik
UP 9: Die „Atmosph
äre“ im Labor
UP 9.4: Fachvortrag
Montag, 22. März 2004, 18:15–18:30, HS 020
Temperature Dependence of Ozone Isotopomer Formation — •Christof Janssen, Dieter Krankowsky, and Konrad Mauersberger — Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg
Oxygen isotope effects in the formation of ozone, O+O2+M→ O3 + M , are unconventional and very large, thus offering a unique atmospheric tracer for atmospheric oxidation involving ozone. Presently, a complete and undisputed understanding of these isotope effects is not available, but differences of zero point energy (ZPE) in the assciation and dissociation of excited ozone are suggested to play a pivotal role.
Here, the results of an improved experimental study of the ozone isotope anomaly are presented. This kinetic study extends earlier room temperature measurements towards the low temperature range of atmospheric interest (233 - 353 K). The technique of molecular beam mass spectrometry (MBMS) has been employed to unravel the relative temperature dependence of 6 out of 36 possible isotopic reactions.
The observed temperature dependence substantiates the role of ZPE for isotopomer fractionation in ozone formation and further completes the understanding of the combined pressure and temperature dependence of atmospheric ozone isotopomer enrichments.