Showing papers by "Yutaka Matsumi published in 2002"

Quantum yields for production of O(1D) in the ultraviolet photolysis of ozone: Recommendation based on evaluation of laboratory data

Abstract: [1] The quantum yield for O( 1 D) production in the photolysis of ozone in the ultraviolet region as a function of wavelength and temperature is a key input for modeling calculations in the atmospheric chemistry. To provide the modeling community with the best possible information, the available data are critically evaluated, and the best possible recommendations for the quantum yields are presented. Since the authors of this paper are the principal investigators of the groups which have provided most of the recent experimental data for the O( 1 D) quantum yields, the basic assumptions made by each group, the input parameters used in obtaining the quantum yields, and possible sources of systematic errors are well examined. The fitting expression of the O( 1 D) yield as a function of photolysis wavelength λ and temperature Tis presented in the ranges of 306 nm < X < 328 nm and 200 K < T < 300 K. The recommendation values of the O( 1 D) quantum yield for 290 nm < X < 306 nm and 328 nm < λ <350 nm are also presented. The formation mechanisms of O( 1 D) in the photolysis of ozone which result in the wavelength and temperature dependence of the O( 1 D) yields are interpreted.

Spectroscopic measurements of tropospheric CO, C2H6, C2H2, and HCN in northern Japan

Abstract: [1] Tropospheric column amounts and mixing ratios of CO, C2H6, C2H2, and HCN were retrieved from ground-based infrared solar spectra using a vertical profile retrieval algorithm (SFIT2). The spectra were recorded with high spectral resolution Fourier transform infrared (FTIR) spectrometers at Moshiri (44.4°N) and Rikubetsu (43.5°N) in northern Japan from May 1995 to June 2000. The retrievals show significant seasonal variations in the tropospheric content of the four molecules over northern Japan with maxima in winter-spring (February–April) for CO, C2H6, and C2H2 and in summer (May–July) for HCN. Good correlations between CO, C2H6, and C2H2 indicated that they had similar sources and underwent similar dilution processes. Deviation of HCN relative to its seasonal mean value (ΔHCN) is correlated with the similar deviation of CO (ΔCO), indicating that enhancements of CO and HCN above the mean levels were probably due to the same sources. Linear trends in tropospheric CO, C2H6, and C2H2 from May 1995 to June 2000 (excluding 1998) were (−2.10 ± 0.30), (−2.53 ± 0.30), and (−3.99 ± 0.57)%/yr, respectively, while the trend of (−0.93 ± 0.49)%/yr in HCN was relatively small. Abnormally high tropospheric amounts of the four molecules were recorded in 1998. HCN amounts were found to be much higher than its seasonal mean value throughout 1998 with a 65% maximum increase in August 1998. Significant increases of CO, C2H6, and C2H2 took place in August–October 1998. Trajectory calculations, global fire maps, and satellite smoke images revealed that biomass burning in eastern Siberia from mid-July to early October 1998 was the major cause of the elevated levels in tropospheric CO, C2H6, C2H2, and HCN observed in northern Japan in 1998.

Quantum yields of O(1D) formation in the photolysis of ozone between 230 and 308 nm

Abstract: [1] Ozone molecules are photolyzed in the strong photoabsorption band of the Hartley band at 230-308 nm, and the O( 3 P j ) photofragments produced by the photolysis are detected directly by a technique of laser-induced fluorescence around 130 nm. The quantum yield values for O( 1 D) formation in the photolysis of ozone at 297 ± 2 K are determined as a function of the photolysis wavelength, using the O( 1 D) quantum yield value of 0.79 at 308 nm as a reference. The O( 1 D) quantum yield values obtained are found to be almost independent of the photolysis wavelength over the Hartley band (∼0.91). The results are compared with the values measured previously using various experimental techniques and also with the recommendation values for use in atmospheric modeling. The effects of the present yield data on the O( 1 D) production rates from ozone photolysis in the stratosphere are evaluated. Impact of our new O( 1 D) quantum yield values on the stratospheric chemistry has also been explored using a one-dimensional photochemical model. The smaller O( 1 D) production rates as compared to the latest NASA/JPL recommendation values are followed by changes in the efficiency of the chemical chain reactions involving HO x , NO x , and ClO x and result in the higher O 3 concentrations throughout the stratosphere.

Nonthermal steady state translational energy distributions of O(1D) atoms in the stratosphere

Abstract: [1] The steady state translational energy distributions of O(1D) in the stratosphere between 20 and 50 km have been studied by laboratory experiments and Monte Carlo simulations. The results indicate that at all altitudes studied the translational energies of stratospheric O(1D) are distributed at high energies more than the Maxwell–Boltzmann distributions of the local temperatures. The predominant source of stratospheric O(1D) atoms is the solar UV photolysis of ozone, and the nascent O(1D) atoms produced have large translational energies due to the excess energy. The average translational energy of O(1D), for instance, at the altitude of 50 km, is found to be about twice as large as the thermal energy at the temperature of the ambient air. The nonthermal steady state translational energy distributions of O(1D) atoms result from the relatively slow translational energy relaxation process compared with the electronic quenching process (1D → 3P) by collisions with ambient air molecules (N2 and O2). It is suggested that the atmospheric reactions involving O(1D) atoms in the stratosphere proceed under nonlocal thermodynamic equilibrium conditions.

Atmospheric lifetime of SF5CF3

Abstract: [1] The vacuum ultraviolet (VUV) absorption spectrum of SF5CF3 was measured over the range 106–200 nm. At 121.6 nm, σ(base e) = (7.8 ± 0.6) × 10−18 cm2 molecule−1, in which quoted uncertainty includes two standard deviation from the least-square fit in the Beer-Lambert plot and our estimate of potential systematic errors associated with measurements of the reactant concentrations. The VUV spectrum and literature data for electron attachment and ion-molecule reactions were incorporated into a model of the stratosphere, mesosphere, and lower thermosphere. This information provides better constraints on the atmospheric lifetime and hence on the potential of this highly radiatively-active trace gas to influence the climate system. The atmospheric lifetime of SF5CF3 is dominated by dissociative electron attachment and is estimated to be approximately 950 years. Solar proton events could reduce this to a lower limit of 650 years.

Laser-Induced Fluorescence Instrument for the Detection of Tropospheric OH Radicals

Abstract: An instrument for the measurement of troposphric OH radical concentrations using a laser-induced fluorescence technique has been developed. Ambient air is expanded through a pinhole into a low-pressure fluorescence cell and irradiated by the second harmonic of a dye laser at a high repetition rate of 1 kHz. The OH radicals are electronically excited using A2Σ+(ν′ = 0) ← X2Π (ν′′ = 0) transitions around 308 nm. The fluorescence from OH radicals is collected by a lens system and detected by a photomultiplier. The photoelectron pulses from the photomultiplier are processed by a photon-counting system. The dynode gate of the photomultiplier and counting gate systems are made to minimize the detection of the chamber and Rayleigh scattering signal. The sensitivity of the developed instrument is calibrated with two methods: one is a long-path absorption technique and the other is a titration technique with simultaneous photolysis of water vapor and oxygen. It is found that the background signal is mainly produce...

Dissociative ionization of ICl studied by ion imaging spectroscopy

Abstract: The speed and angular distributions of I+ ions, produced when ICl molecules were exposed to both ultraviolet and visible radiation at 304+608 nm, 355+608 nm, and 304+532 nm, were measured by velocity map imaging. An intense central feature in the I+ images was observed to be very sensitive to the polarization of the ultraviolet light and is attributed to a dissociative ionization mechanism involving three-body fragmentation: ICl+hv (visible)+3hv (ultraviolet)→I++Cl+e−. The effect of varying the delay between the visible and ultraviolet radiation on the I+ images suggests that an intermediate gateway state of ICl reached by absorption of one photon of visible light mediates the transition to the superexcited dissociative ionization state.

Atmospheric chemistry of CF3CFHOCF3: Reaction with OH radicals, atmospheric lifetime, and global warming potential

Abstract: [1] Smog chamber/FTIR techniques were used to study the OH radical initiated oxidation of CF3CFHOCF3 in 700 torr of air diluent at 296 K. Relative rate techniques were used to measure k1(OH + CF3CFHOCF3) = (1.4 ± 0.3) × 10−15 cm3 molecule−1 s−1. The atmospheric lifetime of CF3CFHOCF3 is estimated to be 40 years. The IR spectrum of CF3CFHOCF3 was measured and used to estimate a global warming potential (relative to CO2, 100 year time horizon) for CF3CFHOCF3 of 4500. Results are discussed with respect to the previous literature data.

Electronic quenching of O(1D) by collisions with O2: A theoretical study in a collinear case

Abstract: Potential energy curves of triplet states for collinear O–O2 were calculated by ab initio CASSCF and MRSDCI methods. We found a pseudocrossing between 1 3Σ− (6 3A″) and 2 3Σ− (7 3A″) states at long O–O2 separation. The electronic quenching reaction, O(1D)+O2(X 3Σg−)→O(3P)+O2(b 1Σg+), is dominated by the nonadiabatic transition via the pseudocrossing. The collision energy dependence of the quenching reaction probability, which is evaluated by Zhu and Nakamura’s formula, is found to be in good agreement with experiment.

Laser-Induced Fluorescence Instrument for the Detection of Tropospheric OH Radicals

Abstract: An instrument for the measurement of troposphric OH radical concentrations using a laser-induced fluorescence technique has been developed. Ambient air is expanded through a pinhole into a low-pressure fluorescence cell and irradiated by the second harmonic of a dye laser at a high repetition rate of 1 kHz. The OH radicals are electronically excited using A 2 Σ + ( ν ′ = 0) ← X 2 Π ( ν ′′ = 0) transitions around 308 nm. The fluorescence from OH radicals is collected by a lens system and detected by a photomultiplier. The photoelectron pulses from the photomultiplier are processed by a photon-counting system. The dynode gate of the photomultiplier and counting gate systems are made to minimize the detection of the chamber and Rayleigh scattering signal. The sensitivity of the developed instrument is calibrated with two methods: one is a long-path absorption technique and the other is a titration technique with simultaneous photolysis of water vapor and oxygen. It is found that the background signal is mainly produced by after-pulse effects in the photomultiplier for the fluorescence detection with a dynode gate system. The minimum detection limit is determined to be 7.0 × 10 5 molecules cm − 3 for OH radicals with a signal-to-noise ratio of 2 and a signal integration time of 60 s.