scholarly journals Four Isotope-Labeled Recombination Pathways of Ozone Formation

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1289
Author(s):  
Dmitri Babikov ◽  
Elizaveta Grushnikova ◽  
Igor Gayday ◽  
Alexander Teplukhin
Keyword(s):  
Isotope Effect ◽  
Theoretical Approach ◽  
Rate Coefficient ◽  
A Priori ◽  
Metastable States ◽  
Rate Coefficients ◽  
Ozone Formation ◽  
Rare Isotope ◽  
The Individual ◽  
Good Agreement

A theoretical approach is developed for the description of all possible recombination pathways in the ozone forming reaction, without neglecting any process a priori, and without decoupling the individual pathways one from another. These pathways become physically distinct when a rare isotope of oxygen is introduced, such as 18O, which represents a sensitive probe of the ozone forming reaction. Each isotopologue of O3 contains two types of physically distinct entrance channels and two types of physically distinct product wells, creating four recombination pathways. Calculations are done for singly and doubly substituted isotopologues of ozone, eight rate coefficients total. Two pathways for the formation of asymmetric ozone isotopomer exhibit rather different rate coefficients, indicating large isotope effect driven by ΔZPE-difference. Rate coefficient for the formation of symmetric isotopomer of ozone (third pathway) is found to be in between of those two, while the rate of insertion pathway is smaller by two orders of magnitude. These trends are in good agreement with experiments, for both singly and doubly substituted ozone. The total formation rates for asymmetric isotopomers are found to be somewhat larger than those for symmetric isotopomers, but not as much as in the experiment. Overall, the distribution of lifetimes is found to be very similar for the metastable states in symmetric and asymmetric ozone isotopomers.

scholarly journals The atmospheric chemistry of sulphuryl fluoride, SO<sub>2</sub>F<sub>2</sub>

2008 ◽  
Vol 8 (6) ◽  
pp. 1547-1557 ◽  
Author(s):  
T. J. Dillon ◽  
A. Horowitz ◽  
J. N. Crowley
Keyword(s):  
Atmospheric Chemistry ◽  
Rate Coefficient ◽  
Relative Rate ◽  
Significant Loss ◽  
Rate Coefficients ◽  
Atmospheric Species ◽  
Upper Limits ◽  
Wall Flow ◽  
Temperature Rate ◽  
Good Agreement

Abstract. The atmospheric chemistry of sulphuryl fluoride, SO2F2, was investigated in a series of laboratory studies. A competitive rate method, using pulsed laser photolysis (PLP) to generate O(1D) coupled to detection of OH by laser induced fluorescence (LIF), was used to determine the overall rate coefficient for the reaction O(1D) + SO2F2 → products (R1) of k1 (220–300 K) = (1.3 ± 0.2) × 10−10 cm3 molecule−1 s−1. Monitoring the O(3P) product (R1a) enabled the contribution (α) of the physical quenching process (in which SO2F2 is not consumed) to be determined as α (225–296 K)=(0.55 ± 0.04). Separate, relative rate measurements at 298 K provided a rate coefficient for reactive loss of O(1D), k1b, of (5.8 ± 0.8) × 10−11 cm3 molecule−1 s−1 in good agreement with the value calculated from (1−α) × k1=(5.9 ± 1.0) × 10−11 cm3 molecule−1 s−1. Upper limits for the rate coefficients for reaction of SO2F2 with OH (R2, using PLP-LIF), and with O3 (R3, static reactor) were determined as k2 (294 K)<1 × 10−15 cm3 molecule−1 s−1 and k3 (294 K)<1 × 10−23 cm3 molecule−1 s−1. In experiments using the wetted-wall flow tube technique, no loss of SO2F2 onto aqueous surfaces was observed, allowing an upper limit for the uptake coefficient of γ(pH 2–12)<1 × 10−7 to be determined. These results indicate that SO2F2 has no significant loss processes in the troposphere, and a very long stratospheric lifetime. Integrated band intensities for SO2F2 infrared absorption features between 6 and 19 μm were obtained, and indicate a significant global warming potential for this molecule. In the course of this work, ambient temperature rate coefficients for the reactions O(1D) with several important atmospheric species were determined. The results (in units of 10−10 cm3 molecule−1 s−1, k(O1D + N2)=(0.33 ± 0.06); k(O1D + N2O)=(1.47 ± 0.2) and k(O1D + H2O)=(1.94 ± 0.5) were in good agreement with other recent determinations.

scholarly journals Direct measurements of OH and other product yields from the HO<sub>2</sub>  + CH<sub>3</sub>C(O)O<sub>2</sub> reaction

2016 ◽  
Vol 16 (6) ◽  
pp. 4023-4042 ◽  
Author(s):  
Frank A. F. Winiberg ◽  
Terry J. Dillon ◽  
Stephanie C. Orr ◽  
Christoph B. M Groß ◽  
Iustinian Bejan ◽  
...  
Keyword(s):  
Rate Coefficient ◽  
Measurement Model ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Secondary Products ◽  
Title Reaction ◽  
Direct Measurements ◽  
Series Of Experiments ◽  
First Time ◽  
Good Agreement

Abstract. The reaction CH3C(O)O2 + HO2  →  CH3C(O)OOH + O2 (Reaction R5a), CH3C(O)OH + O3 (Reaction R5b), CH3 + CO2 + OH + O2 (Reaction R5c) was studied in a series of experiments conducted at 1000 mbar and (293 ± 2) K in the HIRAC simulation chamber. For the first time, products, (CH3C(O)OOH, CH3C(O)OH, O3 and OH) from all three branching pathways of the reaction have been detected directly and simultaneously. Measurements of radical precursors (CH3OH, CH3CHO), HO2 and some secondary products HCHO and HCOOH further constrained the system. Fitting a comprehensive model to the experimental data, obtained over a range of conditions, determined the branching ratios α(R5a)  =  0.37 ± 0.10, α(R5b) =  0.12 ± 0.04 and α(R5c) =  0.51 ± 0.12 (errors at 2σ level). Improved measurement/model agreement was achieved using k(R5)  =  (2.4 ± 0.4)  ×  10−11 cm3 molecule−1 s−1, which is within the large uncertainty of the current IUPAC and JPL recommended rate coefficients for the title reaction. The rate coefficient and branching ratios are in good agreement with a recent study performed by Groß et al. (2014b); taken together, these two studies show that the rate of OH regeneration through Reaction (R5) is more rapid than previously thought. GEOS-Chem has been used to assess the implications of the revised rate coefficients and branching ratios; the modelling shows an enhancement of up to 5 % in OH concentrations in tropical rainforest areas and increases of up to 10 % at altitudes of 6–8 km above the equator, compared to calculations based on the IUPAC recommended rate coefficient and yield. The enhanced rate of acetylperoxy consumption significantly reduces PAN in remote regions (up to 30 %) with commensurate reductions in background NOx.

scholarly journals A self-consistent, multivariate method for the determination of gas-phase rate coefficients, applied to reactions of atmospheric VOCs and the hydroxyl radical

2018 ◽  
Vol 18 (6) ◽  
pp. 4039-4054 ◽  
Author(s):  
Jacob T. Shaw ◽  
Richard T. Lidster ◽  
Danny R. Cryer ◽  
Noelia Ramirez ◽  
Fiona C. Whiting ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Rate Coefficient ◽  
Relative Rate ◽  
Ambient Air ◽  
Rate Coefficients ◽  
Oxidation Reactions ◽  
Simultaneous Study ◽  
The University ◽  
Good Agreement

Abstract. Gas-phase rate coefficients are fundamental to understanding atmospheric chemistry, yet experimental data are not available for the oxidation reactions of many of the thousands of volatile organic compounds (VOCs) observed in the troposphere. Here, a new experimental method is reported for the simultaneous study of reactions between multiple different VOCs and OH, the most important daytime atmospheric radical oxidant. This technique is based upon established relative rate concepts but has the advantage of a much higher throughput of target VOCs. By evaluating multiple VOCs in each experiment, and through measurement of the depletion in each VOC after reaction with OH, the OH + VOC reaction rate coefficients can be derived. Results from experiments conducted under controlled laboratory conditions were in good agreement with the available literature for the reaction of 19 VOCs, prepared in synthetic gas mixtures, with OH. This approach was used to determine a rate coefficient for the reaction of OH with 2,3-dimethylpent-1-ene for the first time; k =  5.7 (±0.3)  ×  10−11 cm3 molecule−1 s−1. In addition, a further seven VOCs had only two, or fewer, individual OH rate coefficient measurements available in the literature. The results from this work were in good agreement with those measurements. A similar dataset, at an elevated temperature of 323 (±10) K, was used to determine new OH rate coefficients for 12 aromatic, 5 alkane, 5 alkene and 3 monoterpene VOC + OH reactions. In OH relative reactivity experiments that used ambient air at the University of York, a large number of different VOCs were observed, of which 23 were positively identified. Due to difficulties with detection limits and fully resolving peaks, only 19 OH rate coefficients were derived from these ambient air samples, including 10 reactions for which data were previously unavailable at the elevated reaction temperature of T =  323 (±10) K.

scholarly journals A self-consistent, multi-variate method for the determination of gas phase rate coefficients, applied to reactions of atmospheric VOCs and the hydroxyl radical

2017 ◽  
Author(s):  
Jacob T. Shaw ◽  
Richard T. Lidster ◽  
Danny R. Cryer ◽  
Noelia Ramirez ◽  
Graham A. Boustead ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Rate Coefficient ◽  
Relative Rate ◽  
Ambient Air ◽  
Rate Coefficients ◽  
Oxidation Reactions ◽  
Oh Reactions ◽  
Simultaneous Study ◽  
Good Agreement

Abstract. Gas-phase rate coefficients are fundamental to understanding atmospheric chemistry, yet experimental data are not available for the oxidation reactions of many of the thousands of volatile organic compounds (VOCs) observed in the troposphere. Here a new experimental method is reported for the simultaneous study of reactions between multiple different VOCs and OH, the most important daytime atmospheric radical oxidant. This technique is based upon established relative rate concepts but has the advantage of a much higher throughput of target VOCs. By evaluating multiple VOCs in each experiment, and through measurement of the depletion in each VOC after reaction with OH, the OH + VOC reaction rate coefficients can be derived. Results from experiments conducted under controlled laboratory conditions were in good agreement with the available literature for the reaction of nineteen VOCs, prepared in synthetic gas mixtures, with OH. This approach was used to determine a rate coefficient for the reaction of OH with 2,3-dimethylpent-1-ene for the first time; k = 5.7 (&amp;pm;0.3) × 10–11–cm3 molecule−1 s−1. In addition, a further seven VOCs had only two, or fewer, individual OH rate coefficient measurements available in the literature. The results from this work were in good agreement with those measurements. A similar dataset, at an elevated temperature of 323 (±10) K, was used to determine new OH rate coefficients for twelve aromatic, five alkane, five alkene and three monoterpene VOC + OH reactions. In OH relative reactivity experiments that used ambient air at the University of York, a large number of different VOCs were observed, of which 23 were positively identified. 19 OH rate coefficients were derived from these ambient air samples, including ten reactions for which data was previously unavailable at the elevated reaction temperature of T = 323 (±10) K.

scholarly journals The atmospheric chemistry of sulphuryl fluoride, SO<sub>2</sub>F<sub>2</sub>

2007 ◽  
Vol 7 (5) ◽  
pp. 15213-15249
Author(s):  
T. J. Dillon ◽  
A. Horowitz ◽  
J. N. Crowley
Keyword(s):  
Atmospheric Chemistry ◽  
Rate Coefficient ◽  
Relative Rate ◽  
Significant Loss ◽  
Rate Coefficients ◽  
Atmospheric Species ◽  
Upper Limits ◽  
Wall Flow ◽  
Temperature Rate ◽  
Good Agreement

Abstract. The atmospheric chemistry of sulphuryl fluoride, SO2F2, was investigated in a series of laboratory studies. A competitive rate method, using pulsed laser photolysis (PLP) to generate O(1D) coupled to detection of OH by laser induced fluorescence (LIF), was used to determine the overall rate coefficient for the reaction O(1D)+SO2F2 → products (R1) of k1 (220–300 K)=(1.3±0.2)×10−10 cm³ molecule−1 s−1. Monitoring the O(³P) product (R1a) enabled the contribution (α) of the physical quenching process (in which SO2F2 is not consumed) to be determined as α1 (225–296 K)=(0.55±0.04). Separate, relative rate measurements at 298 K provided a rate coefficient for reactive loss of O(1D), k1b, of (5.8±0.8)×10−11 cm³ molecule−1 s−1 in good agreement with the value calculated from (1−α)×k1=(5.9±1.0)×10−11 cm³ molecule−1 s−1. Upper limits for the rate coefficients for reaction of SO2F2 with OH (R2, using PLP-LIF), and with O3 (R3, static reactor) were determined as k2 (294 K)<1×10−15 cm³ molecule−1 s−1 and k3 (294 K)<1×10−23 cm³ molecule−1 s−1. In experiments using the wetted-wall flow tube technique, no loss of SO2F2 onto aqueous surfaces was observed, allowing an upper limit for the uptake coefficient of γ(pH 2–12)<1×10−7 to be determined. These results indicate that SO2F2 has no significant loss processes in the troposphere, and a very long stratospheric lifetime. Integrated band intensities for SO2F2 infrared absorption features between 6 and 19 μm were obtained, and indicate a significant global warming potential for this molecule. In the course of this work, ambient temperature rate coefficients for the reactions O(1D) with several important atmospheric species were determined. The results (in units of 10−10 cm³ molecule−1 s−1), k(O1D+N2)=(0.33±0.06); k(O1D+N2O)=(1.47±0.2) and k(O1D+H2O)=(1.94±0.5) were in good agreement with other recent determinations.

scholarly journals Direct measurements of OH and other product yields from the HO<sub>2</sub> + CH<sub>3</sub>C(O)O<sub>2</sub> reaction

2015 ◽  
Vol 15 (20) ◽  
pp. 28815-28866
Author(s):  
F. A. F. Winiberg ◽  
T. J. Dillon ◽  
S. C. Orr ◽  
C. B. M Groß ◽  
I. Bejan ◽  
...  
Keyword(s):  
Rate Coefficient ◽  
Measurement Model ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Secondary Products ◽  
Title Reaction ◽  
Direct Measurements ◽  
Series Of Experiments ◽  
First Time ◽  
Good Agreement

Abstract. The reaction CH3C(O)O2 + HO2 &amp;rightarrow; CH3C(O)OOH + O2 (Reaction R5a), CH3C(O)OH + O3 (Reaction R5b), CH3 + CO2 + OH + O2 (Reaction R5c) was studied in a series of experiments conducted at 1000 mbar and (293 ± 2) K in the HIRAC simulation chamber. For the first time, products, (CH3C(O)OOH, CH3C(O)OH, O3 and OH) from all three branching pathways of the reaction have been detected directly and simultaneously. Measurements of radical precursors (CH3OH, CH3CHO), HO2 and some secondary products HCHO and HCOOH further constrained the system. Fitting a comprehensive model to the experimental data, obtained over a range of conditions, determined the branching ratios α(R5a) = 0.37 ± 0.10, α(R5b) = 0.12 ± 0.04 and α(R5c) = 0.51 ± 0.12 (errors at 2σ level). Improved measurement/model agreement was achieved using k(R5) = (2.4 ± 0.4) × 10-11 cm3 molecule-1 s-1, which is within the large uncertainty of the current IUPAC and JPL recommended rate coefficients for the title reaction. The rate coefficient and branching ratios are in good agreement with a recent study performed by Groß et al. (2014b); taken together, these two studies show that the rate of OH regeneration through Reaction (R5) is more rapid than previously thought. GEOS-Chem has been used to assess the implications of the revised rate coefficients and branching ratios; the modelling shows an enhancement of up to 5 % in OH concentrations in tropical rainforest areas and increases of up to 10 % at altitudes of 6–8 km above the equator, compared to calculations based on the IUPAC recommended rate coefficient and yield. The enhanced rate of acetylperoxy consumption significantly reduces PAN in remote regions (up to 30 %) with commensurate reductions in background NOx.

scholarly journals Communities and the individual: Beyond the liberal–communitarian divide

2021 ◽  
Vol 47 (4) ◽  
pp. 392-401
Author(s):  
Volker Kaul
Keyword(s):  
Personal Autonomy ◽  
A Priori ◽  
Significant Others ◽  
The Self ◽  
Global Perspective ◽  
Self And Identity ◽  
Default Position ◽  
The Individual

Liberalism believes that individuals are endowed a priori with reason or at least agency and it is up to that reason and agency to make choices, commitments and so on. Communitarianism criticizes liberalism’s explicit and deliberate neglect of the self and insists that we attain a self and identity only through the effective recognition of significant others. However, personal autonomy does not seem to be a default position, neither reason nor community is going to provide it inevitably. Therefore, it is so important to go beyond the liberal–communitarian divide. This article is analysing various proposals in this direction, asks about the place of communities and the individual in times of populism and the pandemic and provides a global perspective on the liberal–communitarian debate.

scholarly journals Statistical Uncertainty of DNS in Geometries without Homogeneous Directions

2021 ◽  
Vol 11 (4) ◽  
pp. 1399
Author(s):  
Jure Oder ◽  
Cédric Flageul ◽  
Iztok Tiselj
Keyword(s):  
Channel Flow ◽  
A Priori ◽  
Time Integration ◽  
Navier Stokes ◽  
Statistical Uncertainty ◽  
Time Step ◽  
Order Of Magnitude ◽  
Averaging Time ◽  
The Individual ◽  
Time Required

In this paper, we present uncertainties of statistical quantities of direct numerical simulations (DNS) with small numerical errors. The uncertainties are analysed for channel flow and a flow separation case in a confined backward facing step (BFS) geometry. The infinite channel flow case has two homogeneous directions and this is usually exploited to speed-up the convergence of the results. As we show, such a procedure reduces statistical uncertainties of the results by up to an order of magnitude. This effect is strongest in the near wall regions. In the case of flow over a confined BFS, there are no such directions and thus very long integration times are required. The individual statistical quantities converge with the square root of time integration so, in order to improve the uncertainty by a factor of two, the simulation has to be prolonged by a factor of four. We provide an estimator that can be used to evaluate a priori the DNS relative statistical uncertainties from results obtained with a Reynolds Averaged Navier Stokes simulation. In the DNS, the estimator can be used to predict the averaging time and with it the simulation time required to achieve a certain relative statistical uncertainty of results. For accurate evaluation of averages and their uncertainties, it is not required to use every time step of the DNS. We observe that statistical uncertainty of the results is uninfluenced by reducing the number of samples to the point where the period between two consecutive samples measured in Courant–Friedrichss–Levy (CFL) condition units is below one. Nevertheless, crossing this limit, the estimates of uncertainties start to exhibit significant growth.

scholarly journals Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohamad Akbar Ali ◽  
M. Balaganesh ◽  
Faisal A. Al-Odail ◽  
K. C. Lin
Keyword(s):  
Water Molecule ◽  
Energy Surface ◽  
Rate Coefficient ◽  
Water Concentration ◽  
State Theory ◽  
Rate Coefficients ◽  
Hydrogen Atoms ◽  
Experimental And Theoretical Studies ◽  
Effective Reaction ◽  
Effective Reaction Rate

AbstractThe rate coefficients for OH + CH3OH and OH + CH3OH (+ X) (X = NH3, H2O) reactions were calculated using microcanonical, and canonical variational transition state theory (CVT) between 200 and 400 K based on potential energy surface constructed using CCSD(T)//M06-2X/6-311++G(3df,3pd). The results show that OH + CH3OH is dominated by the hydrogen atoms abstraction from CH3 position in both free and ammonia/water catalyzed ones. This result is in consistent with previous experimental and theoretical studies. The calculated rate coefficient for the OH + CH3OH (8.8 × 10−13 cm3 molecule−1 s−1), for OH + CH3OH (+ NH3) [1.9 × 10−21 cm3 molecule−1 s−1] and for OH + CH3OH (+ H2O) [8.1 × 10−16 cm3 molecule−1 s−1] at 300 K. The rate coefficient is at least 8 order magnitude [for OH + CH3OH(+ NH3) reaction] and 3 orders magnitude [OH + CH3OH (+ H2O)] are smaller than free OH + CH3OH reaction. Our calculations predict that the catalytic effect of single ammonia and water molecule on OH + CH3OH reaction has no effect under tropospheric conditions because the dominated ammonia and water-assisted reaction depends on ammonia and water concentration, respectively. As a result, the total effective reaction rate coefficients are smaller. The current study provides a comprehensive example of how basic and neutral catalysts effect the most important atmospheric prototype alcohol reactions.

scholarly journals Sartres Lösung zur Antinomie der sozialen Realität in der Kritik der dialektischen Vernunft

2020 ◽  
Vol 68 (6) ◽  
pp. 817-847
Author(s):  
Sebastian Gardner
Keyword(s):  
Ethical Theory ◽  
A Priori ◽  
Social Ontology ◽  
Human Freedom ◽  
Philosophical Foundation ◽  
A Posteriori ◽  
Political Reality ◽  
Dialectical Reason ◽  
The Individual

AbstractCritics have standardly regarded Sartre’s Critique of Dialectical Reason as an abortive attempt to overcome the subjectivist individualism of his early philosophy, motivated by a recognition that Being and Nothingness lacks ethical and political significance, but derailed by Sartre’s Marxism. In this paper I offer an interpretation of the Critique which, if correct, shows it to offer a coherent and highly original account of social and political reality, which merits attention both in its own right and as a reconstruction of the philosophical foundation of Marxism. The key to Sartre’s theory of collective and historical existence in the Critique is a thesis carried over from Being and Nothingness: intersubjectivity on Sartre’s account is inherently aporetic, and social ontology reproduces in magnified form its limited intelligibility, lack of transparency, and necessary frustration of the demands of freedom. Sartre’s further conjecture – which can be formulated a priori but requires a posteriori verification – is that man’s collective historical existence may be understood as the means by which the antinomy within human freedom, insoluble at the level of the individual, is finally overcome. The Critique provides therefore the ethical theory promised in Being and Nothingness.

Sign in / Sign up

Export Citation Format

Share Document