- Heterogeneous Chemistry of HBr and HF
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The heterogeneous chemistry of HBr and HF was studied on glass and ice surfaces at 200 K.Physical and reactive uptake were investigated using a cylindrical fast-flow reactor in conjunction with a chemical-ionization mass spectrometer.HF exhibited no measurable uptake on ice or NAT nor did it significantly react with ClONO2 or HOCl.It is inferred that HF would be unreactive on polar stratospheric cloud particle surfaces.Physical adsorption or absorption of HBr was observed onto glass, adsorbed H2O layers on glass, and ice.For the relatively high used, a very large uptake by ice was observed, and we detected no saturation of the surface.HBr reacts efficiently with ClONO2, Cl2, and N2O5, especially on ice and nitric acid ice surfaces.BrCl was observed as the primary product for the reaction HBr + ClONO2.The products HCl and Br2 were observed for the reaction of HBr with Cl2.On the basis of these results, it is likely that HBr would be processed efficiently on ice particles.
- Hanson, David R.,Ravishankara, A. R.
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- The Synthesis of 15N- and 18O-Isotopically-Enriched Nitryl Bromide, IR Matrix Spectra, and Force Fields of BrNO2, cis-BrONO, and trans-BrONO
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The gas phase reaction between BrNO and O3 at low pressure (2 in about 60% yield. In this manner 15N- and 18O-labeled BrNO2 are prepared. In addition, it is shown that BrNO2 also forms by the heterogeneous low-temperature reaction between gaseous BrNO and solid sulfuric acid, doped with H2O2. It can be assumed that BrNO2 may be formed in a similar way under stratospheric conditions. The isotope scrambling in the reaction between BrNO and 18O3 as well as in the gas phase equilibrium BrNO + NO2 ? BrNO2 + NO are investigated. For the equilibrium constant a lower limit of K298 ≥ 1 × 10-3 is deduced from infrared measurements. A detailed IR and Raman study on BrNO2 is performed. Photolysis of matrix-isolated BrNO2 at different wavelengths leads to a mixture of cis- and trans-BrONO. The vibrational data of BrNO2 (6 fundamentals, 7 combinations), cis-BrONO (5 fundamentals, 1 overtone), and trans-BrONO (4 fundamentals, 8 combinations) as well as the calculated force fields are in excellent agreement with the ab initio values, predicted by T. J. Lee (J. Phys. Chem. 1996, 100, 19847).
- Scheffler, Dieter,Willner, Helge
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p. 4500 - 4506
(2008/10/08)
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