0000000000147410
AUTHOR
John P. Burrows
Iodine and mercury resonance lamps for kinetics experiments and their spectra in the far ultraviolet
Electrodeless iodine and mercury iodide radio-frequency discharge lamps have been made to provide intense sources of resonance radiation of iodine and mercury in the 183-253 nm region. Production technology and emission spectra in the ultraviolet and vacuum ultraviolet regions are described. Both lamps (iodine and mercury iodide) are designed and used for monitoring the iodine 2P1/2 (206.163 nm) and 2P3/2 (183.038 nm) level population kinetics after flash photolysis of I2 or other precursor molecules in laboratory experiments. The technique is suitable for the investigation of the gas phase reaction kinetics following the photolysis of I2 in the presence of O3.
Estimation of the emission temperature of an electrodeless discharge lamp and determination of the oscillator strength for the I(2P3/2) 183.038 nm resonance transition
Abstract The 183.038 nm resonance absorption transition of I( 2 P 3/2 ) has been studied using a flash photolysis set-up for gas-phase chemistry and a radio frequency powered electrodeless discharge lamp filled with iodine. The dependence of self-absorption and self-reversal on iodine partial pressure in the discharge volume was measured. The optimum iodine partial pressure, with self-absorption minimized and acceptable intensity, is determined to be approximately 2.5×10 −3 mbar. A method is described to estimate the temperature of the emitting atoms using direct measurements of relative absorption at different absorber concentrations. This yields an emission temperature of 923±50 K. Using …
A Cloud masking algorithm for the XBAER aerosol retrieval using MERIS data
Abstract To determine aerosol optical thickness, AOT, and other geophysical parameters describing conditions in the atmosphere and at the earth's surface by inversion of remote sensing measurements from space based instrumentation, it is necessary to separate ground scenes into cloud free and cloudy or cloud contaminated. Identifying the presence of cloud in a ground scene and establishing an accurate and adequate cloud mask is a challenging task. In this study, measurements by the European Space Agency (ESA) MEdium Resolution Imaging Spectrometer (MERIS) have been used to develop a cloud identification and cloud mask algorithm for preprocessing prior to application of the new algorithm cal…
Contribution of the gas-phase reaction between hydroxyl radical and sulfur dioxide to the sulfate aerosol over West Pacific
Sulfate is among the major components of atmospheric aerosols or fine particulate matters. Aerosols loaded with sulfate result in low air quality, damage to ecosystems, and influences on climate change. Sulfate aerosols could originate from that directly emitted to the atmosphere and that produced by atmospheric physicochemical processes. The latter is generated from sulfur dioxide (SO2) via oxidation either in the gas phase reactions or in the aqueous phase. Several mechanisms of SO2 oxidation have been proposed, but the differentiation of the various mechanisms and identification of the sources remain challenging. To meet this need, a new method to estimate the contribution of the gas-pha…
Retrieval of aerosol optical thickness for desert conditions using MERIS observations during the SAMUM campaign
Approximately 30% of the land surface is arid, having desert or semi-desert conditions. Aerosol originating from these regions plays a significant role in climate and atmospheric chemistry of the atmosphere. Retrieving aerosol properties from space-borne platforms above desert conditions, where the surface reflectance is usually very bright, is a challenging task. The proportion of the surface to top of atmosphere (TOA) reflectance can reach values over 90%, especially for wavelength above 500 nm. For these reasons detailed knowledge of aerosol and surface optical properties from these regions is required to separate atmosphere from intrinsically bright surfaces. An approach to retrieve aer…