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Showing papers by "James B. Burkholder published in 2008"


Journal ArticleDOI
TL;DR: In this article, light absorption by soot or nigrosin dye aerosol particles were measured in the laboratory using a particle soot absorption photometer (PSAP) and a photo-acoustic spectrometer (PAS) to assess the influence of nonabsorbing organic aerosol (OA) on the PSAP measurements.
Abstract: Light absorption by soot or nigrosin dye aerosol particles were measured in the laboratory using a particle soot absorption photometer (PSAP) and a photo-acoustic spectrometer (PAS) to assess the influence of non-absorbing organic aerosol (OA) on the PSAP measurements. For the PSAP, particle light absorption is measured after collection on a filter, whereas for the PAS light absorption is measured while the particles remain suspended in the gas phase. OA was generated from the reaction of α -pinene with ozone. It was observed that the presence of this OA in an external mixture of absorbing aerosol and OA can cause an increase in the light absorption measured by the PSAP, relative to that measured by the PAS, by more than a factor of two. This enhancement in the PSAP absorption was found to increase as the amount of OA increased relative to the absorbing compound. Additionally, experiments where absorbing aerosol was deposited on a PSAP filter prior to addition of OA demonstrated that the non-absorbing OA ...

228 citations


Journal ArticleDOI
TL;DR: The most likely reaction product channels were found to be highly endothermic, consistent with the upper limits of the rate coefficients measured in this work and the global warming potential was calculated.
Abstract: In this work, potential atmospheric loss processes for SO2F2, a commercially used biocide (fumigant), have been studied and its global warming potential calculated. Rate coefficients for the gas-phase reactions OH + SO2F2 --> products, k1, and Cl + SO2F2 --> products, k4, were determined using a relative rate technique to be k1 300, >10000, 700, and >4700 years, respectively. The stratospheric lifetime of SO2F2 is calculated using a two-dimensional model to be 630 years. The global warming potential (GWP) for SO2F2 was calculated to be 4780 for the 100 year time horizon using infrared absorption cross sections measured in this work and a SO2F2 globally averaged atmospheric lifetime of 36 years, which is determined primarily by ocean uptake, reported by Muhle et al. (Muhle, J.; Huang, J.; Weiss, R. F.; Prinn, R. G.; Miller, B. R.; Salameh, P. K.; Harth, C. M.; Fraser, P. J.; Porter, L. W.; Greally, B. R.; O'Doherty, S.; Simonds, P. G. J. Geophys. Res., submitted for publication, 2008). Reaction channels and the possible formation of stable adducts in reactions 1 and 4 were evaluated using ab initio, CCSD(T), and density functional theory, B3P86, quantum mechanical electronic structure calculations. The most likely reaction product channels were found to be highly endothermic, consistent with the upper limits of the rate coefficients measured in this work.

61 citations


Journal ArticleDOI
TL;DR: Comparison of the present results with the single previous determination of k1(296 K) and a discussion of the reaction mechanism and non-Arrhenius temperature dependence are presented are presented.
Abstract: Rate coefficients, k1(T), over the temperature range of 210−390 K are reported for the gas-phase reaction OH + HC(O)C(O)H (glyoxal) → products at pressures between 45 and 300 Torr (He, N2). Rate coefficients were determined under pseudo-first-order conditions in OH using pulsed laser photolysis production of OH radicals coupled with OH detection by laser-induced fluorescence. The rate coefficients obtained were independent of pressure and bath gas. The room-temperature rate coefficient, k1(296 K), was determined to be (9.15 ± 0.8) × 10-12 cm3 molecule-1 s-1. k1(T) shows a negative temperature dependence with a slight deviation from Arrhenius behavior that is reproduced over the temperature range included in this study by k1(T) = [(6.6 ± 0.6) × 10-18]T2[exp([820 ± 30]/T)] cm3 molecule-1 s-1. For atmospheric modeling purposes, a fit to an Arrhenius expression over the temperature range included in this study that is most relevant to the atmosphere, 210−296 K, yields k1(T) = (2.8 ± 0.7) × 10-12 exp[(340 ± 50...

46 citations


Journal ArticleDOI
TL;DR: In this paper, the rate coefficient for the gas-phase reaction OH + CH3CHO (acetaldehyde) was measured over the temperature range 204-373 K using pulsed laser photolytic production of OH coupled with its detection via laser-induced fluorescence.
Abstract: The rate coefficient, k1, for the gas-phase reaction OH + CH3CHO (acetaldehyde) products, was measured over the temperature range 204–373 K using pulsed laser photolytic production of OH coupled with its detection via laser-induced fluorescence. The CH3CHO concentration was measured using Fourier transform infrared spectroscopy, UV absorption at 184.9 nm and gas flow rates. The room temperature rate coefficient and Arrhenius expression obtained are k1(296 K) = (1.52 ± 0.15) × 10−11 cm3 molecule−1 s−1 and k1(T) = (5.32 ± 0.55) × 10−12 exp[(315 ± 40)/T] cm3 molecule−1 s−1. The rate coefficient for the reaction OH (ν = 1) + CH3CHO, k7(T) (where k7 is the rate coefficient for the overall removal of OH (ν = 1)), was determined over the temperature range 204–296 K and is given by k7(T) = (3.5 ± 1.4) × 10−12 exp[(500 ± 90)/T], where k7(296 K) = (1.9 ± 0.6) × 10−11 cm3 molecule−1 s−1. The quoted uncertainties are 2σ (95% confidence level). The preexponential term and the room temperature rate coefficient include estimated systematic errors. k7 is slightly larger than k1 over the range of temperatures included in this study. The results from this study were found to be in good agreement with previously reported values of k1(T) for temperatures <298 K. An expression for k1(T), suitable for use in atmospheric models, in the NASA/JPL and IUPAC format, was determined by combining the present results with previously reported values and was found to be k1(298 K) = 1.5 × 10−11 cm3 molecule−1 s−1, f(298 K) = 1.1, E/R = 340 K, and Δ E/R (or g) = 20 K over the temperature range relevant to the atmosphere. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 635–646, 2008

17 citations


Journal ArticleDOI
TL;DR: The PNA cross sections determined in this work for 3nuOH and 4nuOH will increase calculated atmospheric photolysis rates of PNA slightly, and the action spectrum agreed with the CRDS absorption spectra.
Abstract: Band strengths for the second (3νOH) and third (4νOH) overtones of the OH stretch vibration of peroxynitric acid, HO2NO2 (PNA) in the gas-phase were measured using Cavity Ring-Down Spectroscopy (CRDS). Both OH overtone transitions show diffuse smoothly varying symmetrical absorption profiles without observable rotational structure. Integrated band strengths (base e) at 296 K were determined to be S3νOH = (5.7 ± 1.1) × 10−20 and S4νOH = (4.9 ± 0.9) × 10−21 cm2 molecule−1 cm−1 with peak cross sections of (8.8 ± 1.7) × 10−22 and (7.0 ± 1.3) × 10−23 cm2 molecule−1 at 10086.0 ± 0.2 cm−1 and 13095.8 ± 0.4 cm−1, respectively, using PNA concentrations measured on line by Fourier-transform infrared and ultraviolet absorption spectroscopy. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors in the measurements. OH overtone spectra measured at lower temperature, 231 K, showed a narrowing of the 3νOH band along with an increase in its peak absorption cross section, but no ch...

11 citations