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FP5

THALOZ Résumé de rapport

Project ID: EVK2-CT-2001-00104
Financé au titre de: FP5-EESD
Pays: Germany

Physico-chemical parameter: new ultraviolet absorption cross-sections of BrO at atmospheric temperatures measured by time-windowing Fourier-transform spectroscopy

The UV absorption cross-section spectra of the atmospherically important radical BrO have been determined using the recently developed technique of time-windowing Fourier transform spectroscopy (TW-FTS). The absorption spectra of the A(2)Pi(3/2)-X(2)Pi(3/2) band system were recorded in the flash photolysis of a gaseous mixture of Br-2 and O-3. The bromine-photo sensitised decomposition of O-3 was observed at five different temperatures between 203 and 298 K. The absolute UV absorption cross-section was determined from the time-dependent observation of reactant and product absorptions and by a kinetic analysis of the BrO behaviour. The integrated UV absorption cross-section of BrO was, within the accuracy of the measurements, constant over the temperature range studied, as expected from spectroscopic considerations. For the (7, 0) vibrational band at 29 540cm-1 (338.5nm), the peak absorption cross-sections were determined to be 2.19+/-0.23 at 298K, 2.23+/-0.23 at 273K, 2.52+/-0.26 at 243K, 2.75+/-0.29 at 223K, and 3.03+/-0.31 at 203K (all in units X 10(-17) cm2 per molecule, at a spectral resolution of 3.8 cm-1, with error intervals of 2sigma). Further, vibrational constants and the dissociation limit for the electronic state A(2)Pi(3/2) were derived. The A <-- X dissociation energy was determined to be D-0 = 35 240+/-160cm-1 or 421.6+/-1.9kJ/mol.

Citation: Fleischmann, O.C.; Burrows, J.P.; Hartmann, M.; Orphal, J. New ultraviolet absorption cross-sections of BrO at atmospheric temperatures measured by time-windowing Fourier-transform spectroscopy, Journal of Photochemistry and Photobiology A: Chemistry 168, 117-132, 2004

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