Showing papers by "James B. Burkholder published in 1994"

Ozone depletion and global warming potentials of CF3I

Abstract: Laboratory measurements of the infrared and near-ultraviolet absorption characteristics of CF{sub 3}I (a potentially useful substitute for halons) are presented. Using these data together with a detailed photochemical model, it is shown that the lifetime of this gas in the sunlit atmosphere is less than a day. The chemistry of iodine in the stratosphere is evaluated, and it is shown that any iodine that reaches the stratosphere will be very effective for ozone destruction here. However, the extremely short lifetime of CF{sub 3}I greatly limits its transport to the stratosphere when released at the surface, especially at midlatitudes, and the total anthropogenic surface release of CF{sub 3}I is likely to be far less than that of natural iodocarbons such as CH{sub 3}I on a global basis. It is highly probable that the steady-state ozone depletion potential (ODP) of CF{sub 3}I for surface releases is less than 0.008 and more likely baelow 0.0001. Measured infrared absorption data are also combined with the lifetime to show that the 20-year global warming potential (GWP) of this gas is likely to be very small, less than 5. Therefore this study suggests that neither the ODP nor the GWP of this gas represent significant obstaclesmore » to its use as a replacement for halons. 34 refs., 3 figs., 2 tabs.« less

Temperature dependence of the ozone absorption spectrum over the wavelength range 410 to 760 nm

Abstract: The ozone, O3, absorption cross sections between 410 and 760 nm, the Chappuis band, were measured at 220, 240, 260, and 280 K relative to that at room temperature using a diode array spectrometer. The measured cross sections varied very slightly, less than 1%, with decreasing temperature between 550 and 660 nm, near the peak of the Chappuis band. At wavelengths away from the peak, the absorption cross sections decreased with decreasing temperature; e.g., about 40% at 420 nm between 298 and 220 K. These results are compared with previous measurements and the impact on atmospheric measurements are discussed.

Temperature dependence of the ClONO2 UV absorption spectrum

Abstract: The temperature dependence of the ClONO2 absorption spectrum has been measured between 220 and 298 K and between 195 and 430 nm using a diode array spectrometer. The absorption cross sections were determined using both: (1) absolute pressure measurements at 296 K and (2) measurements at various temperatures relative to 296 K using a dual absorption cell arrangement. The temperature dependence of the ClONO2 absorption spectrum shows very broad structure. The amplitude of the temperature dependence relative to that at 296 K is weak at short wavelengths, less than 2% at 215 nm and 220 K, but significant at the wavelengths important in the stratosphere, about 30% at 325 nm and 220 K. Our ClONO2 absorption cross section data are in good general agreement with the previous measurements of Molina and Molina (1979).