Low energy resonances in the ^18O(α,γ)^22Ne reaction have been measured using a high efficiency G... more Low energy resonances in the ^18O(α,γ)^22Ne reaction have been measured using a high efficiency Ge clover / BGO detector array. The experiment was performed at the Karlsruhe 3.7 MV Van de Graaff accelerator with typical α beam currents of 100 μA. As a result, resonance strengths of 0.71±0.17 μeV and 0.48±0.16 μeV could be obtained for the resonances at 566 and 470 keV, respectively. These data provide a reliable basis for the determination of the reaction rate during stellar He burning.
Using the results obtained over the Ivory Coast during the airborne Tropospheric Ozone campaign (... more Using the results obtained over the Ivory Coast during the airborne Tropospheric Ozone campaign (TROPOZ) I (December 1987) and over West Africa and South America during the meridional airborne campaign TROPOZ II (January 1991), a study is made of biomass burning emissions in the northern African tropics, a region which is much less well documented than that of southern Africa. The analysis of data for 03 and its precursors (CO, CH4, NO, and NOy) confirms the existence of important ozone formations over northern Africa during the Boreal winter with photochemical 03 formation rates of 15-35 ppbv 03 d -•. The distributions obtained over the Ivory Coast show the presence of different layers associated with the Inter Tropical Convergence Zone (ITCZ), with an ozone-and precursor-laden Harmattan layer embedded between the southerly depleted monsoon layer below and the free troposphere easterly circulation above. In front of the ITCZ discontinuity, air parcels of different ages are identified in biomass burning plumes resulting from the transfer to altitude of compounds emitted by fires followed by ascending motions of this polluted air above the monsoon layer. Using a chemical box model, the chemical evolution of concentrations in these air parcels is simulated, confirming the explanations already proposed from the study of the dynamic context and history of the air parcels along their trajectories. The ozone measurements performed during TROPOZ II on both sides of the central Atlantic (Brazil, West Africa) support the hypothesis that because of the prevailing meteorology, smoke-laden air masses emanating from the burning regions in northern Africa can enter a meteorological regime which permits them to be transported out over the Atlantic where they can influence budgets over the south Atlantic Basin during the Austral summer. 1992; Marenco et al., 1990; Fishman and Larsen, 1987; Fishman of 1 to 4 km [Crutzen et a/.,1985; Andreae et al., 1988, 1992]. et al., 1990]. Andreae et al. suggested that the photochemical ozone production West Africa during Dynamique Et Chimie Atmosph6rique en At a global scale, satellite observation shows high levels of Forgt Equatoriale (DECAFE) 1988 and FOS/DECAFE 1991 tropospheric ozone over large areas in the tropics [Fishman and (special issue "
Low energy resonances in the ^18O(α,γ)^22Ne reaction have been measured using a high efficiency G... more Low energy resonances in the ^18O(α,γ)^22Ne reaction have been measured using a high efficiency Ge clover / BGO detector array. The experiment was performed at the Karlsruhe 3.7 MV Van de Graaff accelerator with typical α beam currents of 100 μA. As a result, resonance strengths of 0.71±0.17 μeV and 0.48±0.16 μeV could be obtained for the resonances at 566 and 470 keV, respectively. These data provide a reliable basis for the determination of the reaction rate during stellar He burning.
Using the results obtained over the Ivory Coast during the airborne Tropospheric Ozone campaign (... more Using the results obtained over the Ivory Coast during the airborne Tropospheric Ozone campaign (TROPOZ) I (December 1987) and over West Africa and South America during the meridional airborne campaign TROPOZ II (January 1991), a study is made of biomass burning emissions in the northern African tropics, a region which is much less well documented than that of southern Africa. The analysis of data for 03 and its precursors (CO, CH4, NO, and NOy) confirms the existence of important ozone formations over northern Africa during the Boreal winter with photochemical 03 formation rates of 15-35 ppbv 03 d -•. The distributions obtained over the Ivory Coast show the presence of different layers associated with the Inter Tropical Convergence Zone (ITCZ), with an ozone-and precursor-laden Harmattan layer embedded between the southerly depleted monsoon layer below and the free troposphere easterly circulation above. In front of the ITCZ discontinuity, air parcels of different ages are identified in biomass burning plumes resulting from the transfer to altitude of compounds emitted by fires followed by ascending motions of this polluted air above the monsoon layer. Using a chemical box model, the chemical evolution of concentrations in these air parcels is simulated, confirming the explanations already proposed from the study of the dynamic context and history of the air parcels along their trajectories. The ozone measurements performed during TROPOZ II on both sides of the central Atlantic (Brazil, West Africa) support the hypothesis that because of the prevailing meteorology, smoke-laden air masses emanating from the burning regions in northern Africa can enter a meteorological regime which permits them to be transported out over the Atlantic where they can influence budgets over the south Atlantic Basin during the Austral summer. 1992; Marenco et al., 1990; Fishman and Larsen, 1987; Fishman of 1 to 4 km [Crutzen et a/.,1985; Andreae et al., 1988, 1992]. et al., 1990]. Andreae et al. suggested that the photochemical ozone production West Africa during Dynamique Et Chimie Atmosph6rique en At a global scale, satellite observation shows high levels of Forgt Equatoriale (DECAFE) 1988 and FOS/DECAFE 1991 tropospheric ozone over large areas in the tropics [Fishman and (special issue "
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