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Vieuxmaire OPJ, Nahler NH, Jones JR, Dixon RN, Ashfold MNR. Photodissociation of state selected BrCl cations: Branching ratios and angular anisotropies of the Br product forming channels. Mol Phys 2017. [DOI: 10.1080/00268970500052197a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
| | - N. Hendrik Nahler
- a School of Chemistry , University of Bristol , Bristol , BS8 1TS , UK
| | - J. R. Jones
- a School of Chemistry , University of Bristol , Bristol , BS8 1TS , UK
| | - R. N. Dixon
- a School of Chemistry , University of Bristol , Bristol , BS8 1TS , UK
| | - M. N. R. Ashfold
- a School of Chemistry , University of Bristol , Bristol , BS8 1TS , UK
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2
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Liu F, Fang Y, Chen Y, Liu J. Reactions of Deprotonated Tyrosine and Tryptophan with Electronically Excited Singlet Molecular Oxygen (a1Δg): A Guided-Ion-Beam Scattering, Statistical Modeling, and Trajectory Study. J Phys Chem B 2012; 116:6369-79. [DOI: 10.1021/jp303022b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Fangwei Liu
- Department of Chemistry
and Biochemistry, Queens College and the Graduate Center of the City University of New York,
65-30 Kissena Blvd., Flushing, New York 11367, United States
| | - Yigang Fang
- Department of Chemistry
and Biochemistry, Queens College and the Graduate Center of the City University of New York,
65-30 Kissena Blvd., Flushing, New York 11367, United States
| | - Yun Chen
- Department of Chemistry
and Biochemistry, Queens College and the Graduate Center of the City University of New York,
65-30 Kissena Blvd., Flushing, New York 11367, United States
| | - Jianbo Liu
- Department of Chemistry
and Biochemistry, Queens College and the Graduate Center of the City University of New York,
65-30 Kissena Blvd., Flushing, New York 11367, United States
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Abstract
The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic.
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Affiliation(s)
- William Klemperer
- Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138
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4
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Boyle JM, Uselman BW, Liu J, Anderson SL. Vibrational effects on the reaction of NO2+ with C2H2: Effects of bending and bending angular momentum. J Chem Phys 2008; 128:114304. [DOI: 10.1063/1.2889953] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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5
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Abstract
In the past half century, radioastronomy has changed our perception and understanding of the universe. In this issue of PNAS, the molecular chemistry directly observed within the galaxy is discussed. For the most part, the description of the molecular transformations requires specific kinetic schemes rather than chemical thermodynamics. Ionization of the very abundant molecular hydrogen and atomic helium followed by their secondary reactions is discussed. The rich variety of organic species observed is a challenge for complete understanding. The role and nature of reactions involving grain surfaces as well as new spectroscopic observations of interstellar and circumstellar regions are topics presented in this special feature.
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Affiliation(s)
- William Klemperer
- Department of Chemistry, Harvard University, Cambridge, MA 02138, USA.
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6
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Liu J, Uselman BW, Van Devener B, Anderson SL. Vibrational mode and collision energy effects on reaction of H2CO+ with CO2. Phys Chem Chem Phys 2006; 8:4575-84. [PMID: 17047755 DOI: 10.1039/b610814h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effects of collision energy (Ecol) and five different modes of H2CO+ vibration on the title reaction have been studied over the center-of-mass Ecol range from 0.1 to 3.2 eV, including measurements of product ion recoil velocity distributions. Electronic structure and Rice-Ramsperger-Kassel-Marcus calculations were used to examine properties of various complexes and transition states that might be important along the reaction coordinate. Two product channels are observed, corresponding to Hydrogen Transfer (HT) and Proton Transfer (PT). Both channels are endothermic with similar onset energies of approximately 0.9 eV; however, HT dominates over the entire Ecol range and accounts for 70-85% of the total reaction cross section. Both HT and PT occur by direct mechanisms over the entire Ecol range, and have similar dependence on reactant vibrational and collision energy. Despite these similarities, and the fact that the two channels are nearly isoenergetic and differ only in which product moiety carries the charge, their dynamics appear quite different. PT occurs primarily in large impact parameter stripping collisions, where most of the available energy is partitioned to product recoil. HT, in contrast, results in internally hot products with little recoil energy and a more forward-backward symmetric product velocity distribution. Vibration is found to affect the reaction differently in different collision energy regimes. The appearance thresholds are found to depend only on total energy, i.e., all modes of vibration are equivalent to Ecol. With increasing Ecol, vibrational energy becomes increasingly effective, relative to Ecol, at driving reaction. For HT, this transition occurs just above threshold, while for PT it begins at roughly twice the threshold energy.
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Affiliation(s)
- Jianbo Liu
- Department of Chemistry, University of Utah, 315 S 1400 E, Room 2020, Salt Lake City, UT 84112, USA
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7
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Liu J, Van Devener B, Anderson SL. Vibrational mode and collision energy effects on reaction of H2CO+ with C2H2: Charge state competition and the role of Franck-Condon factors in endoergic charge transfer. J Chem Phys 2005; 123:204313. [PMID: 16351262 DOI: 10.1063/1.2128670] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effects of collision energy (E(col)) and six different H(2)CO(+) vibrational states on the title reaction have been studied over the center-of-mass E(col) range from 0.1 to 2.6 eV, including measurements of product ion recoil velocity distributions. Ab initio and Rice-Ramsperger-Kassel-Marcus calculations were used to examine the properties of complexes and transition states that might be important in mediating the reaction. Reaction is largely direct, despite the presence of multiple deep wells on the potential surface. Five product channels are observed, with a total reaction cross section at the collision limit. The competition among the major H(2) (+) transfer, hydrogen transfer, and proton transfer channels is strongly affected by E(col) and H(2)CO(+) vibrational excitation, providing insight into the factors that control competition and charge state "unmixing" during product separation. One of the more interesting results is that endoergic charge transfer appears to be controlled by Franck-Condon factors, implying that it occurs at large inter-reactant separations, contrary to the expectation that endoergic reactions should require intimate collisions to drive the necessary energy conversion.
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Affiliation(s)
- Jianbo Liu
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
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Liu J, Song K, Hase WL, Anderson SL. Direct Dynamics Trajectory Study of the Reaction of Formaldehyde Cation with D2: Vibrational and Zero-Point Energy Effects on Quasiclassical Trajectories. J Phys Chem A 2005; 109:11376-84. [PMID: 16354024 DOI: 10.1021/jp052615u] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quasiclassical, direct dynamics trajectories have been used to study the reaction of formaldehyde cation with molecular hydrogen, simulating the conditions in an experimental study of H2CO+ vibrational effects on this reaction. Effects of five different H2CO+ modes were probed, and we also examined different approaches to treating zero-point energy in quasiclassical trajectories. The calculated absolute cross-sections are in excellent agreement with experiments, and the results provide insight into the reaction mechanism, product scattering behavior, and energy disposal, and how they vary with impact parameter and reactant state. The reaction is sharply orientation-dependent, even at high collision energies, and both trajectories and experiment find that H2CO+ vibration inhibits reaction. On the other hand, the trajectories do not reproduce the anomalously strong effect of nu2(+) (the CO stretch). The origin of the discrepancy and approaches for minimizing such problems in quasiclassical trajectories are discussed.
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Affiliation(s)
- Jianbo Liu
- Department of Chemistry, University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, USA
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9
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Vieuxmaire OPJ, Nahler NH, Jones JR, Dixon RN, Ashfold * MNR. Photodissociation of state selected BrCl+cations: branching ratios and angular anisotropies of the Br+product forming channels. Mol Phys 2005. [DOI: 10.1080/00268970500052197] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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10
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Liu J, Van Devener B, Anderson SL. Vibrational mode and collision energy effects on reaction of H2CO+ with C2D4. J Chem Phys 2004; 121:11746-59. [PMID: 15634139 DOI: 10.1063/1.1822921] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the effects of collision energy (Ecol) and five different H2CO+ vibrational modes on the reaction of H2CO+ with C2D4 over the center-of-mass E(col) range from 0.1 to 2.1 eV. Properties of various complexes and transition states were also examined computationally. Seven product channels are observed. Charge transfer (CT) has the largest cross section over the entire energy range, substantially exceeding the hard sphere cross section at high energies. Competing with CT are six channels involving transfer of one or more hydrogen atoms or protons and one involving formation of propanal, followed by hydrogen elimination. Despite the existence of multiple deep wells on the potential surface, all reactions go by direct mechanisms, except at the lowest collision energies, where short-lived complexes appear to be important. Statistical complex decay appears adequate to account for the product branching at low collision energies, however, even at the lowest energies, the vibrational effects are counter to statistical expectations. The pattern of Ecol and vibrational mode effects provide insight into factors that control reaction and interchannel competition.
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Affiliation(s)
- Jianbo Liu
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, USA
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11
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Liu J, Uselman B, Van Devener B, Anderson SL. Vibrational Mode Effects as a Probe of Inter-channel Coupling in the Reactions of Formaldehyde Cation with Ammonia and Water. J Phys Chem A 2004. [DOI: 10.1021/jp040352i] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jianbo Liu
- Department of Chemistry, 315 S 1400 E, Room 2020, University of Utah, Salt Lake City, Utah 84112
| | - Brady Uselman
- Department of Chemistry, 315 S 1400 E, Room 2020, University of Utah, Salt Lake City, Utah 84112
| | - Brian Van Devener
- Department of Chemistry, 315 S 1400 E, Room 2020, University of Utah, Salt Lake City, Utah 84112
| | - Scott L. Anderson
- Department of Chemistry, 315 S 1400 E, Room 2020, University of Utah, Salt Lake City, Utah 84112
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12
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Francis GJ, Wilson PF, Maclagan RGAR, Freeman CG, Meot-Ner M, McEwan MJ. Ionic Reactions between Formaldehyde and Hydrocarbons. H2 Transfer as a Hydrogenation Mechanism in Astrochemistry. J Phys Chem A 2004. [DOI: 10.1021/jp048128g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Gregory J. Francis
- Department of Chemistry, University of Canterbury, Christchurch 8001, New Zealand
| | - Paul F. Wilson
- Department of Chemistry, University of Canterbury, Christchurch 8001, New Zealand
| | | | - Colin G. Freeman
- Department of Chemistry, University of Canterbury, Christchurch 8001, New Zealand
| | - Michael Meot-Ner
- Department of Chemistry, University of Canterbury, Christchurch 8001, New Zealand
| | - Murray J. McEwan
- Department of Chemistry, University of Canterbury, Christchurch 8001, New Zealand
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