The Experts below are selected from a list of 1812 Experts worldwide ranked by ideXlab platform
Hua Guo - One of the best experts on this subject based on the ideXlab platform.
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Mode Specificity in the OH + HO2 → H2O + O2 Reaction: Enhancement of Reactivity by Exciting a Spectator Mode
Journal of the American Chemical Society, 2020Co-Authors: Yang Liu, Hongwei Song, Daiqian Xie, Hua GuoAbstract:A reaction typically involves a few active modes while the other modes are largely preserved throughout the reaction as spectators. Excitation of an active mode is expected to promote the reaction, but depositing energy in a spectator mode typically has no effect, because of the differing ability for energy flow to the reaction coordinate. In this work, we report a surprising case of mode specificity in a key radical-radical reaction OH + HO2 → H2O + O2, where such canonical expectations fail to hold. Despite its spectator nature, the vibrational excitation of the OH reactant is shown at low collision energies to enhance the reactivity significantly. This unique effect can be attributed to the increased attraction with HO2 due to the larger dipole of the stretched OH. At low collision energies, the stronger attraction increases the chance of capturing the reactants to form a hydrogen-bonded complex, thus of passing through the Submerged Barrier. The novel mechanism differs from the conventional vibrational enhancement via coupling to the reaction coordinate at the transition state, enriching our understanding of mode specificity in chemistry.
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mode specificity in the oh ho2 h2o o2 reaction enhancement of reactivity by exciting a spectator mode
Journal of the American Chemical Society, 2020Co-Authors: Yang Liu, Hongwei Song, Daiqian Xie, Hua GuoAbstract:A reaction typically involves a few active modes while the other modes are largely preserved throughout the reaction as spectators. Excitation of an active mode is expected to promote the reaction, but depositing energy in a spectator mode typically has no effect, because of the differing ability for energy flow to the reaction coordinate. In this work, we report a surprising case of mode specificity in a key radical-radical reaction OH + HO2 → H2O + O2, where such canonical expectations fail to hold. Despite its spectator nature, the vibrational excitation of the OH reactant is shown at low collision energies to enhance the reactivity significantly. This unique effect can be attributed to the increased attraction with HO2 due to the larger dipole of the stretched OH. At low collision energies, the stronger attraction increases the chance of capturing the reactants to form a hydrogen-bonded complex, thus of passing through the Submerged Barrier. The novel mechanism differs from the conventional vibrational enhancement via coupling to the reaction coordinate at the transition state, enriching our understanding of mode specificity in chemistry.
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Optical Control of Reactions between Water and Laser-Cooled Be+ Ions.
The journal of physical chemistry letters, 2018Co-Authors: Tiangang Yang, Hua Guo, Gary K. Chen, Changjian Xie, Arthur G. Suits, Wesley C. Campbell, Eric R. HudsonAbstract:We investigate reactions between laser-cooled Be+ ions and room-temperature water molecules using an integrated ion trap and high-resolution time-of-flight mass spectrometer. This system allows simultaneous measurement of individual reaction rates that are resolved by reaction product. The rate coefficient of the Be+(2S1/2) + H2O → BeOH+ + H reaction is measured for the first time and is found to be approximately two times smaller than predicted by an ion–dipole capture model. Zero-point-corrected quasi-classical trajectory calculations on a highly accurate potential energy surface for the ground electronic state reveal that the reaction is capture-dominated, but a Submerged Barrier in the product channel lowers the reactivity. Furthermore, laser excitation of the ions from the 2S1/2 ground state to the 2P3/2 state opens new reaction channels, and we report the rate and branching ratio of the Be+(2P3/2) + H2O → BeOH+ + H and H2O+ + Be reactions. The excited-state reactions are nonadiabatic in nature.
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Optical Control of Reactions between Water and Laser-Cooled Be+ Ions
2018Co-Authors: Tiangang Yang, Hua Guo, Gary K. Chen, Changjian Xie, Arthur G. Suits, Wesley C. Campbell, Eric R. HudsonAbstract:We investigate reactions between laser-cooled Be+ ions and room-temperature water molecules using an integrated ion trap and high-resolution time-of-flight mass spectrometer. This system allows simultaneous measurement of individual reaction rates that are resolved by reaction product. The rate coefficient of the Be+(2S1/2) + H2O → BeOH+ + H reaction is measured for the first time and is found to be approximately two times smaller than predicted by an ion–dipole capture model. Zero-point-corrected quasi-classical trajectory calculations on a highly accurate potential energy surface for the ground electronic state reveal that the reaction is capture-dominated, but a Submerged Barrier in the product channel lowers the reactivity. Furthermore, laser excitation of the ions from the 2S1/2 ground state to the 2P3/2 state opens new reaction channels, and we report the rate and branching ratio of the Be+(2P3/2) + H2O → BeOH+ + H and H2O+ + Be reactions. The excited-state reactions are nonadiabatic in nature
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Communication: Highly accurate ozone formation potential and implications for kinetics
The Journal of chemical physics, 2011Co-Authors: Richard Dawes, Phalgun Lolur, Hua GuoAbstract:Atmospheric ozone is formed by the O + O2 exchange reaction followed by collisional stabilization of the O3* intermediate. The dynamics of the O + O2 reaction and to a lesser extent the O3 stabilization depend sensitively on the underlying potential energy surface, particularly in the asymptotic region. Highly accurate Davidson corrected multi-state multi-reference configuration interaction calculations reported here reveal that the minimal energy path for the formation of O3 from O + O2 is a monotonically decaying function of the atom-diatom distance and contains no “reef” feature found in previous ab initio calculations. The absence of a Submerged Barrier leads to an exchange rate constant with the correct temperature dependence and is in better agreement with experiment, as shown by quantum scattering calculations.
Gábor Czakó - One of the best experts on this subject based on the ideXlab platform.
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Rethinking the X- + CH3Y [X = OH, SH, CN, NH2, PH2; Y = F, Cl, Br, I] SN2 reactions.
Physical chemistry chemical physics : PCCP, 2019Co-Authors: Domonkos A. Tasi, Zita Fábián, Gábor CzakóAbstract:Moving beyond the textbook mechanisms of bimolecular nucleophilic substitution (SN2) reactions, we characterize several novel stationary points and pathways for the reactions of X− [X = OH, SH, CN, NH2, PH2] nucleophiles with CH3Y [Y = F, Cl, Br, I] molecules using the high-level explicitly-correlated CCSD(T)-F12b method with the aug-cc-pVnZ(-PP) [n = D, T, Q] basis sets. Besides the not-always-existing traditional pre- and post-reaction ion-dipole complexes, X−⋯H3CY and XCH3⋯Y−, and the Walden-inversion transition state, [X–CH3–Y]−, we find hydrogen-bonded X−⋯HCH2Y (X = OH, CN, NH2; Y ≠ F) and front-side H3CY⋯X− (Y ≠ F) complexes in the entrance and hydrogen-bonded XH2CH⋯Y− (X = SH, CN, PH2) and H3CX⋯Y− (X = OH, SH, NH2) complexes in the exit channels depending on the nucleophile and leaving group as indicated in parentheses. Retention pathways via either a high-energy front-side attack Barrier, XYCH3−, or a novel double-inversion transition state, XH⋯CH2Y−, having lower energy for X = OH, CN, and NH2 and becoming Submerged (Barrier-less) for X = OH and Y = I as well as X = NH2 and Y = Cl, Br, and I, are also investigated.
S.m. Karisiddaiah - One of the best experts on this subject based on the ideXlab platform.
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1300 km long late Pleistocene-Holocene shelf edge Barrier reef system along the western continental shelf of India: occurrence and significance
Marine Geology, 1996Co-Authors: K.h. Vora, B.g. Wagle, M. Veerayya, F. Almeida, S.m. KarisiddaiahAbstract:Abstract A detailed analysis of echosounding and side-scan sonar data collected from the western continental margin of India has revealed the presence of prominent shelf edge reefs, concentrated mostly on the central and the southern parts. Their depth of occurrence varies between 85 and 136 m. The reefs are 1–12 m high and 0.1–2.6 km wide (av. 700 m). Morphologically, they may be classified into (1) simple and (2) complex types. The former are single and broad or narrow (av. width 350 m), while the latter are generally massive (av. width 950 m) with several superimposed peaks. Sub-bottom profiles indicate the presence of paleolagoons. This reef system, more than 1000 km long, trends NNW-SSE i.e., parallel to subparallel to the present-day shoreline. It is surmised that coral/algal reef growth commenced with the advent of the Holocene transgression and favorable antecedent topography, and continued until early Holocene. Subsequently, rapid sea level rise drowned the reefs. The shelf edge reefs, therefore, are part of “relict, Submerged” Barrier reef system and reflect late Pleistocene/early Holocene shoreline.
Domonkos A. Tasi - One of the best experts on this subject based on the ideXlab platform.
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Rethinking the X- + CH3Y [X = OH, SH, CN, NH2, PH2; Y = F, Cl, Br, I] SN2 reactions.
Physical chemistry chemical physics : PCCP, 2019Co-Authors: Domonkos A. Tasi, Zita Fábián, Gábor CzakóAbstract:Moving beyond the textbook mechanisms of bimolecular nucleophilic substitution (SN2) reactions, we characterize several novel stationary points and pathways for the reactions of X− [X = OH, SH, CN, NH2, PH2] nucleophiles with CH3Y [Y = F, Cl, Br, I] molecules using the high-level explicitly-correlated CCSD(T)-F12b method with the aug-cc-pVnZ(-PP) [n = D, T, Q] basis sets. Besides the not-always-existing traditional pre- and post-reaction ion-dipole complexes, X−⋯H3CY and XCH3⋯Y−, and the Walden-inversion transition state, [X–CH3–Y]−, we find hydrogen-bonded X−⋯HCH2Y (X = OH, CN, NH2; Y ≠ F) and front-side H3CY⋯X− (Y ≠ F) complexes in the entrance and hydrogen-bonded XH2CH⋯Y− (X = SH, CN, PH2) and H3CX⋯Y− (X = OH, SH, NH2) complexes in the exit channels depending on the nucleophile and leaving group as indicated in parentheses. Retention pathways via either a high-energy front-side attack Barrier, XYCH3−, or a novel double-inversion transition state, XH⋯CH2Y−, having lower energy for X = OH, CN, and NH2 and becoming Submerged (Barrier-less) for X = OH and Y = I as well as X = NH2 and Y = Cl, Br, and I, are also investigated.
Yang Liu - One of the best experts on this subject based on the ideXlab platform.
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Mode Specificity in the OH + HO2 → H2O + O2 Reaction: Enhancement of Reactivity by Exciting a Spectator Mode
Journal of the American Chemical Society, 2020Co-Authors: Yang Liu, Hongwei Song, Daiqian Xie, Hua GuoAbstract:A reaction typically involves a few active modes while the other modes are largely preserved throughout the reaction as spectators. Excitation of an active mode is expected to promote the reaction, but depositing energy in a spectator mode typically has no effect, because of the differing ability for energy flow to the reaction coordinate. In this work, we report a surprising case of mode specificity in a key radical-radical reaction OH + HO2 → H2O + O2, where such canonical expectations fail to hold. Despite its spectator nature, the vibrational excitation of the OH reactant is shown at low collision energies to enhance the reactivity significantly. This unique effect can be attributed to the increased attraction with HO2 due to the larger dipole of the stretched OH. At low collision energies, the stronger attraction increases the chance of capturing the reactants to form a hydrogen-bonded complex, thus of passing through the Submerged Barrier. The novel mechanism differs from the conventional vibrational enhancement via coupling to the reaction coordinate at the transition state, enriching our understanding of mode specificity in chemistry.
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mode specificity in the oh ho2 h2o o2 reaction enhancement of reactivity by exciting a spectator mode
Journal of the American Chemical Society, 2020Co-Authors: Yang Liu, Hongwei Song, Daiqian Xie, Hua GuoAbstract:A reaction typically involves a few active modes while the other modes are largely preserved throughout the reaction as spectators. Excitation of an active mode is expected to promote the reaction, but depositing energy in a spectator mode typically has no effect, because of the differing ability for energy flow to the reaction coordinate. In this work, we report a surprising case of mode specificity in a key radical-radical reaction OH + HO2 → H2O + O2, where such canonical expectations fail to hold. Despite its spectator nature, the vibrational excitation of the OH reactant is shown at low collision energies to enhance the reactivity significantly. This unique effect can be attributed to the increased attraction with HO2 due to the larger dipole of the stretched OH. At low collision energies, the stronger attraction increases the chance of capturing the reactants to form a hydrogen-bonded complex, thus of passing through the Submerged Barrier. The novel mechanism differs from the conventional vibrational enhancement via coupling to the reaction coordinate at the transition state, enriching our understanding of mode specificity in chemistry.
