scholarly journals The study of intermolecular energy transfers in electronic energy quenching for molecular collisions N<sub>2</sub>-N<sub>2</sub>, N<sub>2</sub>-O<sub>2</sub>, O<sub>2</sub>-O<sub>2</sub>

2008 ◽  
Vol 26 (5) ◽  
pp. 1149-1157 ◽  
Author(s):  
A. S. Kirillov
Keyword(s):  
Vibrational Excitation ◽  
Branching Ratios ◽  
Electronic Energy ◽  
Rate Coefficients ◽  
Molecular Collisions ◽  
Calculated Rate ◽  
Energy Transfers ◽  
Intermolecular Energy ◽  
Product Branching ◽  
Good Agreement

Abstract. Contributions of intermolecular electron energy transfers in the electronic quenching are calculated for molecular collisions N2(A3Σu+, W3Δu)+N2(X1Σg+, v=0), N2(A3Σu+)+N2(X1Σg+, v≥0), N2(A3Σu+)+O2(X3Σg−, v=0–2), O2(a1Δg, b1Σg+)+O2(X3Σg−, v=0–2). The calculation has allowed one to estimate the product branching ratios. It is shown that there is a dependence of the calculated rate coefficients on the vibrational excitation of N2(X1Σg+) and O2(X3Σg−) molecules. In many cases, the calculated rate coefficients have a good agreement with available experimental data.

Barrierless Reactions of Three Benzonitrile Radical Cations with Ethylene

2020 ◽  
Vol 73 (8) ◽  
pp. 705
Author(s):  
Oisin J. Shiels ◽  
P. D. Kelly ◽  
Stephen J. Blanksby ◽  
Gabriel da Silva ◽  
Adam J. Trevitt
Keyword(s):  
Ion Trap ◽  
Radical Cations ◽  
Branching Ratios ◽  
Ring Closure ◽  
Van Der Waals Complexes ◽  
Rate Coefficients ◽  
Ion Trap Mass Spectrometry ◽  
Closure Mechanism ◽  
Product Ions ◽  
Product Branching

Reactions of three protonated benzonitrile radical cations with ethylene are investigated. Product branching ratios and reaction kinetics, measured using ion-trap mass spectrometry, are reported and mechanisms are developed with support from quantum chemical calculations. Reactions proceed via pre-reactive van der Waals complexes with no energy barrier (above the reactant energy) and form radical addition and addition–elimination product ions. Rate coefficients are 4-dehydrobenzonitrilium: 1.72±0.01×10−11 cm3 molecule−1 s−1, 3-dehydrobenzonitrilium: 1.85±0.01×10−11 cm3 molecule−1 s−1, and 2-dehydrobenzonitrilium: 5.96±0.06×10−11 cm3 molecule−1 s−1 (with±50% absolute uncertainty). A ring-closure mechanism involving the protonated nitrile substituent is proposed for the 2-dehydrobenzonitrilium case and suggests favourable formation of the protonated indenimine cation.

Vibrational Excitation and Product Branching Ratios in Dissociation of the Isotopologs of H3O: Experiment and Theory

2013 ◽  
Vol 117 (32) ◽  
pp. 7256-7266 ◽  
Author(s):  
Jennifer E. Mann ◽  
Zhen Xie ◽  
John D. Savee ◽  
Joel M. Bowman ◽  
Robert E. Continetti
Keyword(s):  
Vibrational Excitation ◽  
Branching Ratios ◽  
Product Branching

scholarly journals Prediction of absolute rate coefficients and product branching ratios for the C(3P)+allene reaction system

2002 ◽  
Vol 117 (15) ◽  
pp. 7055-7067 ◽  
Author(s):  
Harold W. Schranz ◽  
Sean C. Smith ◽  
Alexander M. Mebel ◽  
Sheng H. Lin
Keyword(s):  
Reaction System ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Absolute Rate ◽  
Product Branching

Dissociative electron recombination of NH2CHOH+ and implications for interstellar formamide abundance

2019 ◽  
Vol 490 (1) ◽  
pp. 1325-1331 ◽  
Author(s):  
M A Ayouz ◽  
C H Yuen ◽  
N Balucani ◽  
C Ceccarelli ◽  
I F Schneider ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Electron Recombination ◽  
Complex Species ◽  
Star Forming ◽  
Star Forming Regions ◽  
Global Rate ◽  
Cometary Material ◽  
Good Agreement

ABSTRACT Formamide is a potentially important molecule in the context of pre-biotic chemistry, since reactions involving it can lead to precursors of genetic and metabolic molecules. Being abundant in cometary material and in star-forming regions, the formation and destruction routes of interstellar formamide have been the focus of several studies. In this work, we focus on the electron recombination of protonated formamide, an important step of its destruction routes, by performing rigorous ab initio calculations of this process. We found that our values are in good agreement with previous qualitative estimates of the global rate coefficients. On the contrary, we propose a substantial revision of the products and branching ratios. Finally, we justify and emphasize the importance of carrying out similar theoretical calculations on the largest possible number of complex species of astrochemical interest.

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.

Competition between the H- and D-atom transfer channels in the H2O+ + HD reaction: reduced-dimensional quantum and quasi-classical studies

2017 ◽  
Vol 19 (26) ◽  
pp. 17396-17403 ◽  
Author(s):  
Hongwei Song ◽  
Anyang Li ◽  
Minghui Yang ◽  
Hua Guo
Keyword(s):  
Branching Ratios ◽  
Atom Transfer ◽  
Classical Studies ◽  
Product Branching ◽  
Transfer Channels ◽  
Good Agreement

Good agreement is found between theoretical and experimental product branching ratios of the H2O+ + HD reaction.

Rate coefficients and product branching ratios for (E)-2-butenal + H reactions

2020 ◽  
Vol 22 (25) ◽  
pp. 14246-14254
Author(s):  
Maiara Oliveira Passos ◽  
Igor Araujo Lins ◽  
Tiago Vinicius Alves
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Variational Theory ◽  
Hydrogen Atoms ◽  
Small Curvature ◽  
Thermal Rate Constants ◽  
First Time ◽  
Product Branching

Thermal rate constants for the hydrogen abstraction reactions of (E)-2-butenal by hydrogen atoms were calculated, for the first time, using the multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT).

scholarly journals Rate coefficients and product branching ratios for the oxidation of phenyl and naphthyl radicals: A theoretical RRKM-ME study

2015 ◽  
Vol 35 (2) ◽  
pp. 1861-1869 ◽  
Author(s):  
V.V. Kislov ◽  
R.I. Singh ◽  
D.E. Edwards ◽  
A.M. Mebel ◽  
M. Frenklach
Keyword(s):  
Branching Ratios ◽  
Rate Coefficients ◽  
Product Branching

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.

Convergence Properties of Quasiclassical Trajectory Calculations on Dynamics of Autoionization Event in He(23S)-D2 Penning Ionization

1997 ◽  
Vol 62 (2) ◽  
pp. 154-171 ◽  
Author(s):  
Jan Vojtík ◽  
Richard Kotal
Keyword(s):  
Branching Ratios ◽  
Classical Trajectory ◽  
Vibrational States ◽  
Penning Ionization ◽  
Trajectory Calculations ◽  
Quantum Mechanical Treatment ◽  
Total Ionization ◽  
Vibrational Levels ◽  
Degree Of Convergence ◽  
Product Branching

An analysis of the degree of convergence of theoretical pictures of the dynamics of the autoionization event He(23S)-D2(v" = 0) -> [He...D2+(v')] + e is presented for a number of batches of Monte Carlo calculations differing in the number of the trajectories run. The treatment of the dynamics consists in 2D classical trajectory calculations based on static characteristics which include a quantum mechanical treatment of the perturbed D2(v" = 0) and D2+(v') vibrational motion. The vibrational populations are dynamical averages over the local widths of the He(23S)-D2(v" = 0) state with respect to autoionization to D2+(...He) in its v'th vibrational level and the Penning electron energies are related to the local differences between the energies of the corresponding perturbed D2(v" = 0)(...He*) and D2+(v')(...He) vibrational states. Special attention is paid to the connection between the requirements on the degree of convergence of the classical trajectory picture of the event and the purpose of the calculations. Information is obtained regarding a scale of the trajectory calculations required for physically sensible applications of the model to an interpretation of different type of experiments on the system: total ionization cross section measurements, Penning ionization electron spectra, subsequent 3D classical trajectory calculations of branching ratios of the products of the postionization collision process, and interpretation of electron ion coincidence measurements of the product branching ratios for individual vibrational levels of the nascent Penning ion.

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