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• 1. [Article] FAGE measurements of tropospheric HO with measurements and model of interferences

  Ambient HO measurements by low-pressure laser-excited fluorescence with chemical modulation, and supporting ozone and water-vapor data, are presented for periods in May and August 1987. The observed peak ...

  Citation × Citation Citation Abstract Copy Title: FAGE measurements of tropospheric HO with measurements and model of interferences Author: Hard, Thomas M., Mehrabzadeh, A. A., Chan, C. Y., O'Brien, Robert J. Year: 1992 Ambient HO measurements by low-pressure laser-excited fluorescence with chemical modulation, and supporting ozone and water-vapor data, are presented for periods in May and August 1987. The observed peak daytime ambient HO concentrations in Oregon are in the range (2.5 to 8) times106 molecules cm⁻³ and show small negative offsets due to photochemical interference. Direct measurements of the interference at fixed [O₃] give the dependence on ambient [H₂O] and on the modulating reagent [isobutane]. At ambient [O₃]=30 p.p.b. and 10 torr H₂O, with excitation and detection at a total pressure of 4 torr, the net interference is equal to [HO]=-1.3times10⁶ molecule cm⁻³. Title: FAGE measurements of tropospheric HO with measurements and model of interferences Author: Hard, Thomas M., Mehrabzadeh, A. A., Chan, C. Y., O'Brien, Robert J. Year: 1992 Ambient HO measurements by low-pressure laser-excited fluorescence with chemical modulation, and supporting ozone and water-vapor data, are presented for periods in May and August 1987. The observed peak daytime ambient HO concentrations in Oregon are in the range (2.5 to 8) times106 molecules cm⁻³ and show small negative offsets due to photochemical interference. Direct measurements of the interference at fixed [O₃] give the dependence on ambient [H₂O] and on the modulating reagent [isobutane]. At ambient [O₃]=30 p.p.b. and 10 torr H₂O, with excitation and detection at a total pressure of 4 torr, the net interference is equal to [HO]=-1.3times10⁶ molecule cm⁻³. Close

• 2. [Article] Third-generation FAGE instrument for tropospheric hydroxyl radical measurement

  The authors have constructed a single-stage, frequency-doubled, copper vapor laser-pumped dye laser to be used in the measurement of atmospheric hydroxyl radical concentrations. This laser can be tuned ...

  Citation × Citation Citation Abstract Copy Title: Third-generation FAGE instrument for tropospheric hydroxyl radical measurement Author: Chan, C. Y., Hard, Thomas M., Mehrabzadeh, A. A., O'Brien, Robert J. Year: 1990 The authors have constructed a single-stage, frequency-doubled, copper vapor laser-pumped dye laser to be used in the measurement of atmospheric hydroxyl radical concentrations. This laser can be tuned to either the 1← 0 or 0← 0 vibrational transition in the electronic transition ²Sigmalarr²Pi. A new photon counting instrument is used for HO fluorescence detection. Theoretical and experimental studies of instrument performance show better sensitivities and reduced photolytic interferences than have been possible with previous systems based upon Nd:YAG pumping. Title: Third-generation FAGE instrument for tropospheric hydroxyl radical measurement Author: Chan, C. Y., Hard, Thomas M., Mehrabzadeh, A. A., O'Brien, Robert J. Year: 1990 The authors have constructed a single-stage, frequency-doubled, copper vapor laser-pumped dye laser to be used in the measurement of atmospheric hydroxyl radical concentrations. This laser can be tuned to either the 1← 0 or 0← 0 vibrational transition in the electronic transition ²Sigmalarr²Pi. A new photon counting instrument is used for HO fluorescence detection. Theoretical and experimental studies of instrument performance show better sensitivities and reduced photolytic interferences than have been possible with previous systems based upon Nd:YAG pumping. Close

• 3. [Article] Diurnal HO₂ cycles at clean air and urban sites in the troposphere

  HO₂ concentrations have been determined at two Oregon sites for continuous periods of 36 to 48 hours, using fluorescence assay with gas expansion. At the sea level coastal site (45degN 124degW), NNW winds ...

  Citation × Citation Citation Abstract Copy Title: Diurnal HO₂ cycles at clean air and urban sites in the troposphere Author: Hard, Thomas M., Chan, C. Y., Mehrabzadeh, A. A., O'Brien, Robert J. Year: 1992 HO₂ concentrations have been determined at two Oregon sites for continuous periods of 36 to 48 hours, using fluorescence assay with gas expansion. At the sea level coastal site (45degN 124degW), NNW winds prevailed during daytime, and a point measurement of very low total nonmethane hydrocarbon concentration indicated the presence of remote tropospheric air of oceanic origin. At the urban site, HO₂ was determined during moderately low ozone pollution levels. At both sites, maximum daily [HO₂] was in the range of 1-2times10⁸ cm⁻³ under clear-sky conditions, with an estimated overall uncertainty of 40%. Title: Diurnal HO₂ cycles at clean air and urban sites in the troposphere Author: Hard, Thomas M., Chan, C. Y., Mehrabzadeh, A. A., O'Brien, Robert J. Year: 1992 HO₂ concentrations have been determined at two Oregon sites for continuous periods of 36 to 48 hours, using fluorescence assay with gas expansion. At the sea level coastal site (45degN 124degW), NNW winds prevailed during daytime, and a point measurement of very low total nonmethane hydrocarbon concentration indicated the presence of remote tropospheric air of oceanic origin. At the urban site, HO₂ was determined during moderately low ozone pollution levels. At both sites, maximum daily [HO₂] was in the range of 1-2times10⁸ cm⁻³ under clear-sky conditions, with an estimated overall uncertainty of 40%. Close