You can find below the publication list of all members of the theoretical chemistry group at ENS. For the list of each individual member, please consult their personal webpage from the Members page.
1986 |
Probability Oscillations in Single Pass Curve Crossings: Semiclassical Predictions of Nonmonotonic Dependence on Crossing Velocity Article de journal D J Nesbitt; J T Hynes The Journal of Chemical Physics, 84 (3), p. 1554-1564, 1986, (cited By 4). @article{Nesbitt19861554, title = {Probability Oscillations in Single Pass Curve Crossings: Semiclassical Predictions of Nonmonotonic Dependence on Crossing Velocity}, author = {D J Nesbitt and J T Hynes}, doi = {10.1063/1.450500}, year = {1986}, date = {1986-01-01}, journal = {The Journal of Chemical Physics}, volume = {84}, number = {3}, pages = {1554-1564}, abstract = {We consider dynamical curve crossing behavior for one dimensional intermolecular potentials of arbitrary curvature. Our focus is threefold. (1)A semiclassical WKB formalism yields simple analytic expressions for time dependent transition probabilities throughout the crossing region. For low velocities $upsilon$, our results reduce to the required quasistatic unitary transformation between diabatic and adiabatic representations. At higher $upsilon$, the WKB solutions exhibit time dependent oscillations ("beating" between the stationary adiabatic states) in excellent quantitative agreement with exact numerical solutions. (2) The WKB analysis indicates that an oscillatory dependence of curve crossing probability P cr on $upsilon$ occurs for potential crossings of sufficient curvature, in qualitative disagreement with the extensively used Landau-Zener expression. These probability oscillations can be understood and predicted from simple considerations of potential curvature and coupling strengths. (3) We explore this oscillatory behavior for realistic curve crossing geometries. The results indicate that a nonmonotonic dependence of P cr on velocity may occur in real molecular systems and could be experimentally observed in favorable albeit special circumstances. Even in the absence of oscillations, however, pronounced departure from Landau-Zener predictions can be anticipated. textcopyright 1986 American Institute of Physics.}, note = {cited By 4}, keywords = {}, pubstate = {published}, tppubtype = {article} } We consider dynamical curve crossing behavior for one dimensional intermolecular potentials of arbitrary curvature. Our focus is threefold. (1)A semiclassical WKB formalism yields simple analytic expressions for time dependent transition probabilities throughout the crossing region. For low velocities $upsilon$, our results reduce to the required quasistatic unitary transformation between diabatic and adiabatic representations. At higher $upsilon$, the WKB solutions exhibit time dependent oscillations ("beating" between the stationary adiabatic states) in excellent quantitative agreement with exact numerical solutions. (2) The WKB analysis indicates that an oscillatory dependence of curve crossing probability P cr on $upsilon$ occurs for potential crossings of sufficient curvature, in qualitative disagreement with the extensively used Landau-Zener expression. These probability oscillations can be understood and predicted from simple considerations of potential curvature and coupling strengths. (3) We explore this oscillatory behavior for realistic curve crossing geometries. The results indicate that a nonmonotonic dependence of P cr on velocity may occur in real molecular systems and could be experimentally observed in favorable albeit special circumstances. Even in the absence of oscillations, however, pronounced departure from Landau-Zener predictions can be anticipated. textcopyright 1986 American Institute of Physics. |
Classical Dynamics of Intramolecular Energy Flow and Overtone-Induced Dissociation in HO2H and HO2D Article de journal T Uzer; J T Hynes; W P Reinhardt The Journal of Chemical Physics, 85 (10), p. 5791-5804, 1986, (cited By 90). @article{Uzer19865791, title = {Classical Dynamics of Intramolecular Energy Flow and Overtone-Induced Dissociation in HO2H and HO2D}, author = {T Uzer and J T Hynes and W P Reinhardt}, doi = {10.1063/1.451541}, year = {1986}, date = {1986-01-01}, journal = {The Journal of Chemical Physics}, volume = {85}, number = {10}, pages = {5791-5804}, abstract = {A detailed classical trajectory study of the overtone-induced dissociation of hydrogen peroxide HO2H and its isotopic variant HO2D is presented. The factors affecting intramolecular energy flow, such as nonlinear resonances and the various couplings, are examined in detail. The dissociation lifetimes are found to be on the order of picoseconds and comparable with statistical lifetimes, although the intramolecular energy redistribution is not complete within the lifetime of the molecules. Lifetime broadening contributes very little to the rather large width of the overtone excitation feature, which we conclude is in the main inhomogeneously broadened by rotational structure instead. The implications of our results are discussed. textcopyright 1986 American Institute of Physics.}, note = {cited By 90}, keywords = {}, pubstate = {published}, tppubtype = {article} } A detailed classical trajectory study of the overtone-induced dissociation of hydrogen peroxide HO2H and its isotopic variant HO2D is presented. The factors affecting intramolecular energy flow, such as nonlinear resonances and the various couplings, are examined in detail. The dissociation lifetimes are found to be on the order of picoseconds and comparable with statistical lifetimes, although the intramolecular energy redistribution is not complete within the lifetime of the molecules. Lifetime broadening contributes very little to the rather large width of the overtone excitation feature, which we conclude is in the main inhomogeneously broadened by rotational structure instead. The implications of our results are discussed. textcopyright 1986 American Institute of Physics. |
Molecular Dynamics of the A+BC Reaction in Rare Gas Solution Article de journal J P Bergsma; J R Reimers; K R Wilson; J T Hynes The Journal of Chemical Physics, 85 (10), p. 5625-5643, 1986, (cited By 123). @article{Bergsma19865625, title = {Molecular Dynamics of the A+BC Reaction in Rare Gas Solution}, author = {J P Bergsma and J R Reimers and K R Wilson and J T Hynes}, doi = {10.1063/1.451576}, year = {1986}, date = {1986-01-01}, journal = {The Journal of Chemical Physics}, volume = {85}, number = {10}, pages = {5625-5643}, abstract = {Molecular dynamics are computed for model atom transfers A+BC$rightarrow$AB+C in rare gas solvents at liquid densities. We find that the reaction dynamics can be understood in terms of a simple picture which consists of three stages: (1) activation of reactants, (2) barrier crossing, and (3) deactivation of products. The effects seen in stages (1) and (3) can be largely interpreted in terms of existing models of energy and phase decay in solution, while the effects seen in stage (2) can be largely interpreted in terms of gas phase A+BC barrier crossing dynamics. We find that transition state theory is in perfect agreement with the simulations for the 20 and 10 kcal/mol barrier reactions and is a very good description for a 5 kcal/mol reaction barrier. At low barrier curvature, dynamical effects due to the solvent are shown to induce some recrossings of the transition state barrier, thus causing rate constants calculated by simple transition state theory to be slightly too high. The Grote-Hynes modification of transition state theory, which considers the effect of the time dependent friction of the solvent on the dynamics at the transition state, predicts corrections to the rate constants in good agreement with the results from the simulations. textcopyright 1986 American Institute of Physics.}, note = {cited By 123}, keywords = {}, pubstate = {published}, tppubtype = {article} } Molecular dynamics are computed for model atom transfers A+BC$rightarrow$AB+C in rare gas solvents at liquid densities. We find that the reaction dynamics can be understood in terms of a simple picture which consists of three stages: (1) activation of reactants, (2) barrier crossing, and (3) deactivation of products. The effects seen in stages (1) and (3) can be largely interpreted in terms of existing models of energy and phase decay in solution, while the effects seen in stage (2) can be largely interpreted in terms of gas phase A+BC barrier crossing dynamics. We find that transition state theory is in perfect agreement with the simulations for the 20 and 10 kcal/mol barrier reactions and is a very good description for a 5 kcal/mol reaction barrier. At low barrier curvature, dynamical effects due to the solvent are shown to induce some recrossings of the transition state barrier, thus causing rate constants calculated by simple transition state theory to be slightly too high. The Grote-Hynes modification of transition state theory, which considers the effect of the time dependent friction of the solvent on the dynamics at the transition state, predicts corrections to the rate constants in good agreement with the results from the simulations. textcopyright 1986 American Institute of Physics. |
1985 |
Coriolis-Induced Intramolecular Vibrational Energy Flow between Anharmonic Normal Modes Article de journal T Uzer; G A Natanson; J T Hynes Chemical Physics Letters, 122 (1-2), p. 12-18, 1985, (cited By 49). @article{Uzer198512, title = {Coriolis-Induced Intramolecular Vibrational Energy Flow between Anharmonic Normal Modes}, author = {T Uzer and G A Natanson and J T Hynes}, doi = {10.1016/0009-2614(85)85469-5}, year = {1985}, date = {1985-01-01}, journal = {Chemical Physics Letters}, volume = {122}, number = {1-2}, pages = {12-18}, abstract = {The classical flow of energy between anharmonic normal vibrational modes induced by Coriolis coupling is studied for a simple model of a linear triatomic molecule rotating in a plane. The dynamics are analytically solved via a mapping onto a hindered rotor representation. The theory is confirmed by trajectory calculations. textcopyright 1985.}, note = {cited By 49}, keywords = {}, pubstate = {published}, tppubtype = {article} } The classical flow of energy between anharmonic normal vibrational modes induced by Coriolis coupling is studied for a simple model of a linear triatomic molecule rotating in a plane. The dynamics are analytically solved via a mapping onto a hindered rotor representation. The theory is confirmed by trajectory calculations. textcopyright 1985. |
Overtone-Induced Dissociation of Hydrogen Peroxide: A Classical Trajectory Study Article de journal T Uzer; J T Hynes; W P Reinhardt Chemical Physics Letters, 117 (6), p. 600-605, 1985, (cited By 58). @article{Uzer1985600, title = {Overtone-Induced Dissociation of Hydrogen Peroxide: A Classical Trajectory Study}, author = {T Uzer and J T Hynes and W P Reinhardt}, doi = {10.1016/0009-2614(85)80309-2}, year = {1985}, date = {1985-01-01}, journal = {Chemical Physics Letters}, volume = {117}, number = {6}, pages = {600-605}, abstract = {The overtone-induced dissociation of hydrogen peroxide is studied by classical trajectories. The dissociation lifetimes are found to be on the order of picoseconds and comparable with statistical lifetimes, although energy redistribution is not complete. We conclude that overtone vibrational excitation features are negligibly lifetime-broadened by reaction. textcopyright 1985.}, note = {cited By 58}, keywords = {}, pubstate = {published}, tppubtype = {article} } The overtone-induced dissociation of hydrogen peroxide is studied by classical trajectories. The dissociation lifetimes are found to be on the order of picoseconds and comparable with statistical lifetimes, although energy redistribution is not complete. We conclude that overtone vibrational excitation features are negligibly lifetime-broadened by reaction. textcopyright 1985. |
A Model Study of Overtone-Induced Isomerization: The Role of Non-Linear Resonances Article de journal T Uzer; J T Hynes Chemical Physics Letters, 113 (5), p. 483-488, 1985, (cited By 28). @article{Uzer1985483, title = {A Model Study of Overtone-Induced Isomerization: The Role of Non-Linear Resonances}, author = {T Uzer and J T Hynes}, doi = {10.1016/0009-2614(85)80085-3}, year = {1985}, date = {1985-01-01}, journal = {Chemical Physics Letters}, volume = {113}, number = {5}, pages = {483-488}, abstract = {Overtone-induced isomerization is studied in a simple model for unimolecular isomerization. Considerable reaction rate enhancement occurs for certain initial overtone excitations, and the reactivity patterns differ markedly from those expected from statistical ideas. The critical role of bend-stretch Fermi resonance in this model process is discussed. textcopyright 1985.}, note = {cited By 28}, keywords = {}, pubstate = {published}, tppubtype = {article} } Overtone-induced isomerization is studied in a simple model for unimolecular isomerization. Considerable reaction rate enhancement occurs for certain initial overtone excitations, and the reactivity patterns differ markedly from those expected from statistical ideas. The critical role of bend-stretch Fermi resonance in this model process is discussed. textcopyright 1985. |
Double Well Isomerization Rate Constants in Solution Article de journal A G Zawadzki; J T Hynes Chemical Physics Letters, 113 (5), p. 476-482, 1985, (cited By 67). @article{Zawadzki1985476, title = {Double Well Isomerization Rate Constants in Solution}, author = {A G Zawadzki and J T Hynes}, doi = {10.1016/0009-2614(85)80084-1}, year = {1985}, date = {1985-01-01}, journal = {Chemical Physics Letters}, volume = {113}, number = {5}, pages = {476-482}, abstract = {The rate constant k for a double well isomerization in solution is calculated over the entire friction range. The importance of frequency-dependent friction for both the vibrational energy transfer (VET) and barrier passage components of k is described. Rapid suppression of the VET transfer component with increasing degrees of freedom is discussed. textcopyright 1985.}, note = {cited By 67}, keywords = {}, pubstate = {published}, tppubtype = {article} } The rate constant k for a double well isomerization in solution is calculated over the entire friction range. The importance of frequency-dependent friction for both the vibrational energy transfer (VET) and barrier passage components of k is described. Rapid suppression of the VET transfer component with increasing degrees of freedom is discussed. textcopyright 1985. |
Time-Dependent Fluorescence Solvent Shifts, Dielectric Friction, and Nonequilibrium Solvation in Polar Solvents Article de journal G Van Der Zwan; J T Hynes Journal of Physical Chemistry, 89 (20), p. 4181-4188, 1985, (cited By 493). @article{VanDerZwan19854181, title = {Time-Dependent Fluorescence Solvent Shifts, Dielectric Friction, and Nonequilibrium Solvation in Polar Solvents}, author = {G Van Der Zwan and J T Hynes}, doi = {10.1021/j100266a008}, year = {1985}, date = {1985-01-01}, journal = {Journal of Physical Chemistry}, volume = {89}, number = {20}, pages = {4181-4188}, abstract = {The dynamics of time-dependent fluorescence (TDF) shifts subsequent to electronic absorption by a solute in polar solvents is discussed. It is shown that the TDF shift is directly proportional to the time-dependent dielectric friction $zeta$(t) on the absorbing molecule. This relationship points to the possibility of direct experimental determination of $zeta$(t). In addition, several approximate models which go beyond a simple Debye description are discussed. These models include solvent inertia and solvent polarization relaxation via translation and suggest that non-Debye behavior in TDF shifts might be observable. The connection of the TDF shift to related nonequilibrium solvation effects in chemical reactions in polar solvents is briefly described. textcopyright 1985 American Chemical Society.}, note = {cited By 493}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamics of time-dependent fluorescence (TDF) shifts subsequent to electronic absorption by a solute in polar solvents is discussed. It is shown that the TDF shift is directly proportional to the time-dependent dielectric friction $zeta$(t) on the absorbing molecule. This relationship points to the possibility of direct experimental determination of $zeta$(t). In addition, several approximate models which go beyond a simple Debye description are discussed. These models include solvent inertia and solvent polarization relaxation via translation and suggest that non-Debye behavior in TDF shifts might be observable. The connection of the TDF shift to related nonequilibrium solvation effects in chemical reactions in polar solvents is briefly described. textcopyright 1985 American Chemical Society. |
CHEMICAL REACTION DYNAMICS IN SOLUTION. Livre J T Hynes 1985, (cited By 324). @book{Hynes1985573, title = {CHEMICAL REACTION DYNAMICS IN SOLUTION.}, author = {J T Hynes}, year = {1985}, date = {1985-01-01}, volume = {36}, abstract = {In contrast to the gas phase, where reactants (usually) follow their route to products in splendid isolation, the ubiquitous solvent molecules in solution continually perturb the reactants in their course. The first way in which a solvent medium can affect a reaction rate is via a modification of the activation (free) energy. The second way in which a solvent can influence a reaction rate is via frictional, collisional effects. This review focuses on key prototypical solution reaction types and the progress that has been made in their elucidation. These are radical recombinations, atom transfers, isomerizations, charge transfers, and tunneling reactions.}, note = {cited By 324}, keywords = {}, pubstate = {published}, tppubtype = {book} } In contrast to the gas phase, where reactants (usually) follow their route to products in splendid isolation, the ubiquitous solvent molecules in solution continually perturb the reactants in their course. The first way in which a solvent medium can affect a reaction rate is via a modification of the activation (free) energy. The second way in which a solvent can influence a reaction rate is via frictional, collisional effects. This review focuses on key prototypical solution reaction types and the progress that has been made in their elucidation. These are radical recombinations, atom transfers, isomerizations, charge transfers, and tunneling reactions. |
1984 |
A Simple Dipole Isomerization Model for Non-Equilibrium Solvation Dynamics in Reactions in Polar Solvents Article de journal G van der Zwan; J T Hynes Chemical Physics, 90 (1-2), p. 21-35, 1984, (cited By 102). @article{vanderZwan198421, title = {A Simple Dipole Isomerization Model for Non-Equilibrium Solvation Dynamics in Reactions in Polar Solvents}, author = {G {van der Zwan} and J T Hynes}, doi = {10.1016/0301-0104(84)85078-8}, year = {1984}, date = {1984-01-01}, journal = {Chemical Physics}, volume = {90}, number = {1-2}, pages = {21-35}, abstract = {A simple model for dipole isomerization reactions in polar solvents is studied. A full dynamical treatment at the generalized Langevin equation level reveals several non-equilibrium solvation regimes in which the rate constant differs considerably from the standard equilibrium solvation, transition state theory predictions. In addition, the solvent is found to be heavily involved in the reaction coordinate, in contrast to the standard equilibrium solvation view. The marked differences from a Kramers Langevin equation level description are also described. In each regime, the rate constant and reaction coordinate are found analytically, and typical reaction system-solvent trajectories are displayed. A related normal-mode description convenient for strong reaction system-nearest-neighbor solvent dipole interactions is constructed. In this perspective, non-equilibrium solvation effects on rates and reaction coordinates are interpreted in terms of a bias of the reactive motion towards the direction of least friction. textcopyright 1984.}, note = {cited By 102}, keywords = {}, pubstate = {published}, tppubtype = {article} } A simple model for dipole isomerization reactions in polar solvents is studied. A full dynamical treatment at the generalized Langevin equation level reveals several non-equilibrium solvation regimes in which the rate constant differs considerably from the standard equilibrium solvation, transition state theory predictions. In addition, the solvent is found to be heavily involved in the reaction coordinate, in contrast to the standard equilibrium solvation view. The marked differences from a Kramers Langevin equation level description are also described. In each regime, the rate constant and reaction coordinate are found analytically, and typical reaction system-solvent trajectories are displayed. A related normal-mode description convenient for strong reaction system-nearest-neighbor solvent dipole interactions is constructed. In this perspective, non-equilibrium solvation effects on rates and reaction coordinates are interpreted in terms of a bias of the reactive motion towards the direction of least friction. textcopyright 1984. |
Quantum Dynamic Analysis of Energy Transfer in Model Hydrocarbons Article de journal J S Hutchinson; J T Hynes; W P Reinhardt Chemical Physics Letters, 108 (4), p. 353-358, 1984, (cited By 39). @article{Hutchinson1984353, title = {Quantum Dynamic Analysis of Energy Transfer in Model Hydrocarbons}, author = {J S Hutchinson and J T Hynes and W P Reinhardt}, doi = {10.1016/0009-2614(84)85205-7}, year = {1984}, date = {1984-01-01}, journal = {Chemical Physics Letters}, volume = {108}, number = {4}, pages = {353-358}, abstract = {The quantum dynamic flow of energy out of an initially excited CH bond in a model hydrocarbon is calculated numerically. The results are interpreted in terms of a state-to-state flow of probability and contrasted to classical trajectory, ensemble averages. We show that quantum energy flow has a direct classical interpretation in terms of sequential non-linear resonances. We also present evidence for and the mechanism of significant short-time non-classical effects in the quantum energy flow. textcopyright 1984.}, note = {cited By 39}, keywords = {}, pubstate = {published}, tppubtype = {article} } The quantum dynamic flow of energy out of an initially excited CH bond in a model hydrocarbon is calculated numerically. The results are interpreted in terms of a state-to-state flow of probability and contrasted to classical trajectory, ensemble averages. We show that quantum energy flow has a direct classical interpretation in terms of sequential non-linear resonances. We also present evidence for and the mechanism of significant short-time non-classical effects in the quantum energy flow. textcopyright 1984. |
Classical Dynamics of Highly Excited CH and CD Overtones in Benzene and Perdeuterobenzene Article de journal E L Sibert III; J T Hynes; W P Reinhardt The Journal of Chemical Physics, 81 (3), p. 1135-1144, 1984, (cited By 160). @article{SibertIII19841135, title = {Classical Dynamics of Highly Excited CH and CD Overtones in Benzene and Perdeuterobenzene}, author = {E L Sibert III and J T Hynes and W P Reinhardt}, doi = {10.1063/1.447806}, year = {1984}, date = {1984-01-01}, journal = {The Journal of Chemical Physics}, volume = {81}, number = {3}, pages = {1135-1144}, abstract = {The classical decay of highly excited CH and CD overtones of benzene and perdeuterobenzene is examined by trajectory techniques. The character, mechanism, and time scale of these decays are in striking qualitative agreement with those found in the preceding quantum study by Sibert, Reinhardt, and Hynes. The classical coupling mechanism for the decay is shown to be nonlinear Fermi resonance involving the CH(D) stretch and the in-plane CCH(D) wag. The decay path is described in terms of overlapping nonlinear resonance interactions. textcopyright 1984 American Institute of Physics.}, note = {cited By 160}, keywords = {}, pubstate = {published}, tppubtype = {article} } The classical decay of highly excited CH and CD overtones of benzene and perdeuterobenzene is examined by trajectory techniques. The character, mechanism, and time scale of these decays are in striking qualitative agreement with those found in the preceding quantum study by Sibert, Reinhardt, and Hynes. The classical coupling mechanism for the decay is shown to be nonlinear Fermi resonance involving the CH(D) stretch and the in-plane CCH(D) wag. The decay path is described in terms of overlapping nonlinear resonance interactions. textcopyright 1984 American Institute of Physics. |
Intramolecular Vibrational Relaxation and Spectra of CH and CD Overtones in Benzene and Perdeuterobenzene Article de journal E L Sibert III; W P Reinhardt; J T Hynes The Journal of Chemical Physics, 81 (3), p. 1115-1134, 1984, (cited By 323). @article{SibertIII19841115, title = {Intramolecular Vibrational Relaxation and Spectra of CH and CD Overtones in Benzene and Perdeuterobenzene}, author = {E L Sibert III and W P Reinhardt and J T Hynes}, doi = {10.1063/1.447805}, year = {1984}, date = {1984-01-01}, journal = {The Journal of Chemical Physics}, volume = {81}, number = {3}, pages = {1115-1134}, abstract = {A theoretical model is presented for the vibrational dynamics of highly excited CH and CD overtones in benzene and perdeuterobenzene. The origin, path, and time scale for the overtone relaxation are described. The critical near resonant interaction responsible for the energy flow from an excited CH(D) oscillator to the ring is a Fermi resonance coupling, identified by Sibert, Reinhardt, and Hynes [Chem. Phys. Lett. 92, 455 (1982)]. Quantum overtone spectra are calculated both from time independent and time dependent perspectives and good qualitative agreement is found with the experimental overtone spectra of Reddy, Heller, and Berry [J. Chem. Phys. 76, 2814 (1982)]. Some expected consequences for future experiments on benzene and related systems are indicated. textcopyright 1984 American Institute of Physics.}, note = {cited By 323}, keywords = {}, pubstate = {published}, tppubtype = {article} } A theoretical model is presented for the vibrational dynamics of highly excited CH and CD overtones in benzene and perdeuterobenzene. The origin, path, and time scale for the overtone relaxation are described. The critical near resonant interaction responsible for the energy flow from an excited CH(D) oscillator to the ring is a Fermi resonance coupling, identified by Sibert, Reinhardt, and Hynes [Chem. Phys. Lett. 92, 455 (1982)]. Quantum overtone spectra are calculated both from time independent and time dependent perspectives and good qualitative agreement is found with the experimental overtone spectra of Reddy, Heller, and Berry [J. Chem. Phys. 76, 2814 (1982)]. Some expected consequences for future experiments on benzene and related systems are indicated. textcopyright 1984 American Institute of Physics. |
Quantum Dynamics of Energy Transfer between Bonds in Coupled Morse Oscillator Systems Article de journal J S Hutchinson; E L Sibert III; J T Hynes The Journal of Chemical Physics, 81 (3), p. 1314-1326, 1984, (cited By 58). @article{Hutchinson19841314, title = {Quantum Dynamics of Energy Transfer between Bonds in Coupled Morse Oscillator Systems}, author = {J S Hutchinson and E L Sibert III and J T Hynes}, doi = {10.1063/1.447763}, year = {1984}, date = {1984-01-01}, journal = {The Journal of Chemical Physics}, volume = {81}, number = {3}, pages = {1314-1326}, abstract = {The quantum dynamic flow of energy between coupled anharmonic bonds is calculated and analyzed for ABA triatomics with a massive central atom. The time dependence of quantum "normal mode" states is found to be classical in nature, but for states which are classically local, purely quantum energy flow between bonds occurs. We show that the mechanism for this quantum energy flow between local modes can be understood as an indirect state-to-state flow of probability, involving normal mode intermediary states. In particular, there is a regime in which rapid energy flow-which is classically forbidden-occurs from nonclassical states in the quantum case. Criteria are presented for the existence of purely quantum, and classically impossible, flow of energy between oscillators. Initially prepared states are accordingly classified as normal mode states, quantum local mode states, or nonclassical states, according to the extent and rate of bond-bond energy flow, the sensitivity of the process to small asymmetries, and the participation of intermediary states in the probability flow. Implications for intramolecular energy flow in large molecules and the connection with "dynamic tunneling" are discussed. textcopyright 1984 American Institute of Physics.}, note = {cited By 58}, keywords = {}, pubstate = {published}, tppubtype = {article} } The quantum dynamic flow of energy between coupled anharmonic bonds is calculated and analyzed for ABA triatomics with a massive central atom. The time dependence of quantum "normal mode" states is found to be classical in nature, but for states which are classically local, purely quantum energy flow between bonds occurs. We show that the mechanism for this quantum energy flow between local modes can be understood as an indirect state-to-state flow of probability, involving normal mode intermediary states. In particular, there is a regime in which rapid energy flow-which is classically forbidden-occurs from nonclassical states in the quantum case. Criteria are presented for the existence of purely quantum, and classically impossible, flow of energy between oscillators. Initially prepared states are accordingly classified as normal mode states, quantum local mode states, or nonclassical states, according to the extent and rate of bond-bond energy flow, the sensitivity of the process to small asymmetries, and the participation of intermediary states in the probability flow. Implications for intramolecular energy flow in large molecules and the connection with "dynamic tunneling" are discussed. textcopyright 1984 American Institute of Physics. |
Frequency-Dependent Friction and Solution Reaction Rates Article de journal R F Grote; G Van Der Zwan; J T Hynes Journal of Physical Chemistry, 88 (20), p. 4676-4684, 1984, (cited By 70). @article{Grote19844676, title = {Frequency-Dependent Friction and Solution Reaction Rates}, author = {R F Grote and G Van Der Zwan and J T Hynes}, doi = {10.1021/j150664a047}, year = {1984}, date = {1984-01-01}, journal = {Journal of Physical Chemistry}, volume = {88}, number = {20}, pages = {4676-4684}, abstract = {The influence of frequency-dependent friction as a measure of reaction system-solvent dynamic interaction is investigated for the rates of model atom transfers in solution. A realistic time-dependent-friction model based on previous molecular dynamics simulations is used in a generalized Langevin equation description. The short-time "collisional" aspects of the friction are shown to be often quite important, in contrast to the predictions of a simple Langevin equation Kramers description. They can lead, for example, to an increase of the rate constant k with viscosity as opposed to the expected decrease, and to a failure of k to "track" the long-time hydrodynamic ingredients of the friction. Some experimental evidence on this last feature is noted. The connection of the impulsive collision approximation to the frequency-dependent friction to the BGK model is described. textcopyright 1984 American Chemical Society.}, note = {cited By 70}, keywords = {}, pubstate = {published}, tppubtype = {article} } The influence of frequency-dependent friction as a measure of reaction system-solvent dynamic interaction is investigated for the rates of model atom transfers in solution. A realistic time-dependent-friction model based on previous molecular dynamics simulations is used in a generalized Langevin equation description. The short-time "collisional" aspects of the friction are shown to be often quite important, in contrast to the predictions of a simple Langevin equation Kramers description. They can lead, for example, to an increase of the rate constant k with viscosity as opposed to the expected decrease, and to a failure of k to "track" the long-time hydrodynamic ingredients of the friction. Some experimental evidence on this last feature is noted. The connection of the impulsive collision approximation to the frequency-dependent friction to the BGK model is described. textcopyright 1984 American Chemical Society. |
1983 |
Polarization Diffusion Effects on Reaction Rates in Polar Solvents Article de journal G Van Der Zwan; J T Hynes Chemical Physics Letters, 101 (4-5), p. 367-371, 1983, (cited By 67). @article{VanDerZwan1983367, title = {Polarization Diffusion Effects on Reaction Rates in Polar Solvents}, author = {G Van Der Zwan and J T Hynes}, doi = {10.1016/0009-2614(83)87496-X}, year = {1983}, date = {1983-01-01}, journal = {Chemical Physics Letters}, volume = {101}, number = {4-5}, pages = {367-371}, abstract = {The influence of solvent dipole translational relaxation via the mechanism of polarization diffusion is examined for simple models of dipole isomerization and charge transfer reactions in polar solvents. In certain solvents, e.g. methanol, polarization diffusion has marked effects on reaction rate constants when compared to the Debye orientational solvent relaxation picture. textcopyright 1983.}, note = {cited By 67}, keywords = {}, pubstate = {published}, tppubtype = {article} } The influence of solvent dipole translational relaxation via the mechanism of polarization diffusion is examined for simple models of dipole isomerization and charge transfer reactions in polar solvents. In certain solvents, e.g. methanol, polarization diffusion has marked effects on reaction rate constants when compared to the Debye orientational solvent relaxation picture. textcopyright 1983. |
Polarization Diffusion and Dielectric Friction Article de journal G Van der Zwan; J T Hynes Physica A: Statistical Mechanics and its Applications, 121 (1-2), p. 227-252, 1983, (cited By 53). @article{VanderZwan1983227, title = {Polarization Diffusion and Dielectric Friction}, author = {G {Van der Zwan} and J T Hynes}, doi = {10.1016/0378-4371(83)90253-4}, year = {1983}, date = {1983-01-01}, journal = {Physica A: Statistical Mechanics and its Applications}, volume = {121}, number = {1-2}, pages = {227-252}, abstract = {Relaxation of nonequilibrium polarization fields in dielectrics is usually theoretically treated solely in terms of the reorientational motion of the polar molecules. If, however, the translational diffusion of these molecules is also taken into account, dielectric relaxation is accelerated. This results in the lowering of the dielectric friction that retards the motion of an ion or dipole in a dielectric. This reduction in dielectric friction is here calculated for two models: a time-dependent dipole at the center of a sphere, and a moving charge on the axis of a cylinder, each immersed in a dielectric. A parameter measuring the relative importance of rotation and diffusion is identified, and a substantial lowering of the dielectric friction is implied in many situations. It is shown that the boundary conditions play a decisive role in the properties of the fields. Directions for a further development of the theory of polarization diffusion are indicated. textcopyright 1983.}, note = {cited By 53}, keywords = {}, pubstate = {published}, tppubtype = {article} } Relaxation of nonequilibrium polarization fields in dielectrics is usually theoretically treated solely in terms of the reorientational motion of the polar molecules. If, however, the translational diffusion of these molecules is also taken into account, dielectric relaxation is accelerated. This results in the lowering of the dielectric friction that retards the motion of an ion or dipole in a dielectric. This reduction in dielectric friction is here calculated for two models: a time-dependent dipole at the center of a sphere, and a moving charge on the axis of a cylinder, each immersed in a dielectric. A parameter measuring the relative importance of rotation and diffusion is identified, and a substantial lowering of the dielectric friction is implied in many situations. It is shown that the boundary conditions play a decisive role in the properties of the fields. Directions for a further development of the theory of polarization diffusion are indicated. textcopyright 1983. |
Nonequilibrium Solvation Dynamics in Solution Reactions Article de journal G Van Der Zwan; J T Hynes The Journal of Chemical Physics, 78 (6), p. 4174-4185, 1983, (cited By 231). @article{VanDerZwan19834174, title = {Nonequilibrium Solvation Dynamics in Solution Reactions}, author = {G Van Der Zwan and J T Hynes}, doi = {10.1063/1.445094}, year = {1983}, date = {1983-01-01}, journal = {The Journal of Chemical Physics}, volume = {78}, number = {6}, pages = {4174-4185}, abstract = {We construct a theoretical framework for the description of nonequilibrium solvation and solvent participation in the reaction coordinate for solution reactions. The framework is illustrated by a model of reactive dipole isomerization. We show that a multidimensional reaction coordinate picture is equivalent to a one dimensional description in which a generalized friction characterizes and quantifies nonequilibrium solvation effects on the reaction rate. The adiabatic regime where equilibrium solvation and mean potential ideas are correct is identified. Several distinct regimes of nonequilibrium solvation are identified and described in molecular terms. In the effective mass regime, equilibrium solvation ideas give the reaction barrier curvature correctly, but solvent inertia modifies the barrier passage rate. In the nonadiabatic regime, the solvent is "frozen" during the barrier passage and cannot provide equilibrium solvation. In the polarization caging regime, the reacting species adjust to the moving solvent, rather than vice versa, and the solvent is heavily involved in the reaction coordinate. The rate constant in each of these regimes is related to reactive and solvent dynamics. textcopyright 1983 American Institute of Physics.}, note = {cited By 231}, keywords = {}, pubstate = {published}, tppubtype = {article} } We construct a theoretical framework for the description of nonequilibrium solvation and solvent participation in the reaction coordinate for solution reactions. The framework is illustrated by a model of reactive dipole isomerization. We show that a multidimensional reaction coordinate picture is equivalent to a one dimensional description in which a generalized friction characterizes and quantifies nonequilibrium solvation effects on the reaction rate. The adiabatic regime where equilibrium solvation and mean potential ideas are correct is identified. Several distinct regimes of nonequilibrium solvation are identified and described in molecular terms. In the effective mass regime, equilibrium solvation ideas give the reaction barrier curvature correctly, but solvent inertia modifies the barrier passage rate. In the nonadiabatic regime, the solvent is "frozen" during the barrier passage and cannot provide equilibrium solvation. In the polarization caging regime, the reacting species adjust to the moving solvent, rather than vice versa, and the solvent is heavily involved in the reaction coordinate. The rate constant in each of these regimes is related to reactive and solvent dynamics. textcopyright 1983 American Institute of Physics. |
Current Status of Transition-State Theory Article de journal D G Truhlar; W L Hase; J T Hynes Journal of Physical Chemistry, 87 (15), p. 2664-2682, 1983, (cited By 591). @article{Truhlar19832664, title = {Current Status of Transition-State Theory}, author = {D G Truhlar and W L Hase and J T Hynes}, doi = {10.1021/j100238a003}, year = {1983}, date = {1983-01-01}, journal = {Journal of Physical Chemistry}, volume = {87}, number = {15}, pages = {2664-2682}, abstract = {We review the current status of transition-state theory. We focus on the validity of its basic assumptions and of corrections to and improvements of conventional transition-state theory. The review is divided into sections concerned in turn with bimolecular reactions in the gas phase, unimolecular reactions in the gas phase, and isomerizations and atom-transfer reactions in liquid-phase solutions. Some aspects that are emphasized are variational transition-state theory, tunneling, the assumption of an equilibrium distribution of reactants, and the frictional effects of solvent molecules. textcopyright 1983 American Chemical Society.}, note = {cited By 591}, keywords = {}, pubstate = {published}, tppubtype = {article} } We review the current status of transition-state theory. We focus on the validity of its basic assumptions and of corrections to and improvements of conventional transition-state theory. The review is divided into sections concerned in turn with bimolecular reactions in the gas phase, unimolecular reactions in the gas phase, and isomerizations and atom-transfer reactions in liquid-phase solutions. Some aspects that are emphasized are variational transition-state theory, tunneling, the assumption of an equilibrium distribution of reactants, and the frictional effects of solvent molecules. textcopyright 1983 American Chemical Society. |
Fermi Resonance from a Curvilinear Perspective Article de journal E L Sibert III; J T Hynes; W P Reinhardt Journal of Physical Chemistry, 87 (12), p. 2032-2037, 1983, (cited By 100). @article{SibertIII19832032, title = {Fermi Resonance from a Curvilinear Perspective}, author = {E L Sibert III and J T Hynes and W P Reinhardt}, doi = {10.1021/j100235a004}, year = {1983}, date = {1983-01-01}, journal = {Journal of Physical Chemistry}, volume = {87}, number = {12}, pages = {2032-2037}, abstract = {A curvilinear coordinate approach to Fermi resonance is presented. Anharmonic kinetic coupling between internal coordinates in this perspective is derived and discussed. An application to CO2 is presented. It is found that anharmonic kinetic couplings dominate over anharmonic potential couplings in the Fermi resonance for CO2. Advantages of the curvilinear representation are discussed. textcopyright 1983 American Chemical Society.}, note = {cited By 100}, keywords = {}, pubstate = {published}, tppubtype = {article} } A curvilinear coordinate approach to Fermi resonance is presented. Anharmonic kinetic coupling between internal coordinates in this perspective is derived and discussed. An application to CO2 is presented. It is found that anharmonic kinetic couplings dominate over anharmonic potential couplings in the Fermi resonance for CO2. Advantages of the curvilinear representation are discussed. textcopyright 1983 American Chemical Society. |
1982 |
Intramolecular Vibrational Relaxation of CH Overtones in Benzene Article de journal E L Sibert III; W P Reinhardt; J T Hynes Chemical Physics Letters, 92 (5), p. 455-458, 1982, (cited By 108). @article{SibertIII1982455, title = {Intramolecular Vibrational Relaxation of CH Overtones in Benzene}, author = {E L Sibert III and W P Reinhardt and J T Hynes}, doi = {10.1016/0009-2614(82)87038-3}, year = {1982}, date = {1982-01-01}, journal = {Chemical Physics Letters}, volume = {92}, number = {5}, pages = {455-458}, abstract = {A realistic molecular model is constructed and analyzed for intramolecular vibrational relaxation of CH overtones in benzene. Calculated overtone lineshapes are in good agreement with experiment. textcopyright 1982.}, note = {cited By 108}, keywords = {}, pubstate = {published}, tppubtype = {article} } A realistic molecular model is constructed and analyzed for intramolecular vibrational relaxation of CH overtones in benzene. Calculated overtone lineshapes are in good agreement with experiment. textcopyright 1982. |
Slow Vibrational Relaxation in Picosecond Iodine Recombination in Liquids Article de journal D J Nesbitt; J T Hynes The Journal of Chemical Physics, 77 (4), p. 2130-2143, 1982, (cited By 124). @article{Nesbitt19822130, title = {Slow Vibrational Relaxation in Picosecond Iodine Recombination in Liquids}, author = {D J Nesbitt and J T Hynes}, doi = {10.1063/1.444019}, year = {1982}, date = {1982-01-01}, journal = {The Journal of Chemical Physics}, volume = {77}, number = {4}, pages = {2130-2143}, abstract = {A characteristic time scale of order 100 ps has been observed by several workers in picosecond spectroscopy experiments on iodine recombination in liquid CCl4 and other solvents. This time scale has been thought to be associated with the diffusive relative motion, prior to actual recombination, of photodissociated I atoms. In this paper, we point out that extensive vibrational deactivation of nascent iodine molecules formed in the recombination is required for spectroscopic detection of I2. We propose that slow vibrational relaxation of nascent I2 may play an important role in such recombination studies. We examine the relaxation of highly vibrationally excited I2 in liquid CCl4. Both vibrational-translational (VT) and vibrational-vibrational (VV) energy transfer mechanisms are considered. We estimate that the characteristic time scale for the vibrational relaxation of I2 in CCl4 is of order 100 ps. VV energy transfer is found to play a critical role in the relaxation. Possible experimental avenues for testing our conclusions are suggested. textcopyright 1982 American Institute of Physics.}, note = {cited By 124}, keywords = {}, pubstate = {published}, tppubtype = {article} } A characteristic time scale of order 100 ps has been observed by several workers in picosecond spectroscopy experiments on iodine recombination in liquid CCl4 and other solvents. This time scale has been thought to be associated with the diffusive relative motion, prior to actual recombination, of photodissociated I atoms. In this paper, we point out that extensive vibrational deactivation of nascent iodine molecules formed in the recombination is required for spectroscopic detection of I2. We propose that slow vibrational relaxation of nascent I2 may play an important role in such recombination studies. We examine the relaxation of highly vibrationally excited I2 in liquid CCl4. Both vibrational-translational (VT) and vibrational-vibrational (VV) energy transfer mechanisms are considered. We estimate that the characteristic time scale for the vibrational relaxation of I2 in CCl4 is of order 100 ps. VV energy transfer is found to play a critical role in the relaxation. Possible experimental avenues for testing our conclusions are suggested. textcopyright 1982 American Institute of Physics. |
Hydrodynamic Interaction Effects on Isomerization Rates in Chain Molecules Article de journal B M Ladanyi; J T Hynes The Journal of Chemical Physics, 77 (9), p. 4739-4746, 1982, (cited By 7). @article{Ladanyi19824739, title = {Hydrodynamic Interaction Effects on Isomerization Rates in Chain Molecules}, author = {B M Ladanyi and J T Hynes}, doi = {10.1063/1.444377}, year = {1982}, date = {1982-01-01}, journal = {The Journal of Chemical Physics}, volume = {77}, number = {9}, pages = {4739-4746}, abstract = {The influence of hydrodynamic interaction effects on isomerization rates in chain molecules in solution is studied for a simple model. Attention is focused on the many particle reaction coordinate by which isomerization proceeds. It is found that the rate can be either enhanced or reduced by hydrodynamic interaction effects, depending on activation barrier and conformational properties. In the non-Markovian regime, particle friction and hydrodynamics interaction effects on the rate are diminished, and the transition state theory limit is approached. textcopyright 1982 American Institute of Physics.}, note = {cited By 7}, keywords = {}, pubstate = {published}, tppubtype = {article} } The influence of hydrodynamic interaction effects on isomerization rates in chain molecules in solution is studied for a simple model. Attention is focused on the many particle reaction coordinate by which isomerization proceeds. It is found that the rate can be either enhanced or reduced by hydrodynamic interaction effects, depending on activation barrier and conformational properties. In the non-Markovian regime, particle friction and hydrodynamics interaction effects on the rate are diminished, and the transition state theory limit is approached. textcopyright 1982 American Institute of Physics. |
Energy Diffusion-Controlled Reactions in Solution Article de journal R F Grote; J T Hynes The Journal of Chemical Physics, 77 (7), p. 3736-3743, 1982, (cited By 123). @article{Grote19823736, title = {Energy Diffusion-Controlled Reactions in Solution}, author = {R F Grote and J T Hynes}, doi = {10.1063/1.444277}, year = {1982}, date = {1982-01-01}, journal = {The Journal of Chemical Physics}, volume = {77}, number = {7}, pages = {3736-3743}, abstract = {The energy diffusion-controlled limit for reactions in solution is discussed for anharmonic oscillator models of isomerization and dissociation-recombination. Energy diffusion is described by an equation due to Zwanzig. The vibrational energy diffusion coefficient in this equation is related to the spectrum of solvent forces on the oscillator probed at its unperturbed frequencies. The energy diffusion-controlled rate constants k are calculated. For small barrier heights, k is severely depressed by inefficient, adiabatic regime vibrational energy transfer. For large barrier heights, the important energy flow region lies in the more efficient nonadiabatic vibrational energy transfer regime, and k is much larger. The relevance of our results for solution reactions is discussed. textcopyright 1982 American Institute of Physics.}, note = {cited By 123}, keywords = {}, pubstate = {published}, tppubtype = {article} } The energy diffusion-controlled limit for reactions in solution is discussed for anharmonic oscillator models of isomerization and dissociation-recombination. Energy diffusion is described by an equation due to Zwanzig. The vibrational energy diffusion coefficient in this equation is related to the spectrum of solvent forces on the oscillator probed at its unperturbed frequencies. The energy diffusion-controlled rate constants k are calculated. For small barrier heights, k is severely depressed by inefficient, adiabatic regime vibrational energy transfer. For large barrier heights, the important energy flow region lies in the more efficient nonadiabatic vibrational energy transfer regime, and k is much larger. The relevance of our results for solution reactions is discussed. textcopyright 1982 American Institute of Physics. |
Reactive Paths in the Diffusion Limit Article de journal G Van Der Zwan; J T Hynes The Journal of Chemical Physics, 77 (3), p. 1295-1301, 1982, (cited By 41). @article{VanDerZwan19821295, title = {Reactive Paths in the Diffusion Limit}, author = {G Van Der Zwan and J T Hynes}, doi = {10.1063/1.443951}, year = {1982}, date = {1982-01-01}, journal = {The Journal of Chemical Physics}, volume = {77}, number = {3}, pages = {1295-1301}, abstract = {The character of the reactive motion in multidimensional passage over a chemical barrier in the diffusion limit is examined. Frictional coupling between the reactive and nonreactive modes that are defined by the potential forces leads to an enhancement of the rate constant. This effect arises from a bias of the reactive motion towards the direction of least friction, and is modulated by the potential forces. A detailed explanation of this effect is presented and an application to a simple model of isomerization in polymers is given. textcopyright 1982 American Institute of Physics.}, note = {cited By 41}, keywords = {}, pubstate = {published}, tppubtype = {article} } The character of the reactive motion in multidimensional passage over a chemical barrier in the diffusion limit is examined. Frictional coupling between the reactive and nonreactive modes that are defined by the potential forces leads to an enhancement of the rate constant. This effect arises from a bias of the reactive motion towards the direction of least friction, and is modulated by the potential forces. A detailed explanation of this effect is presented and an application to a simple model of isomerization in polymers is given. textcopyright 1982 American Institute of Physics. |
Dynamical Polar Solvent Effects on Solution Reactions: A Simple Continuum Model Article de journal G Van Der Zwan; J T Hynes The Journal of Chemical Physics, 76 (6), p. 2993-3001, 1982, (cited By 240). @article{VanDerZwan19822993, title = {Dynamical Polar Solvent Effects on Solution Reactions: A Simple Continuum Model}, author = {G Van Der Zwan and J T Hynes}, doi = {10.1063/1.443392}, year = {1982}, date = {1982-01-01}, journal = {The Journal of Chemical Physics}, volume = {76}, number = {6}, pages = {2993-3001}, abstract = {The influence of polar solvent dynamics in solution reactions is investigated for a simple model. In this model, a charge is subject to a chemical free energy barrier, the successful crossing of which constitutes reaction. The retarding influence of the time dependent solvent polarization is described at the continuum Debye relaxation level. The reaction rate constant k is determined as a function of the barrier curvature, the charge-solvent interaction strength, and the solvent polarization relaxation time. The reduction of k with increasingly slower solvent relaxation is found to depend sensitively on the magnitude of charge-solvent interactions. When the latter are weak, the behavior of k differs qualitatively from a standard Kramers prediction. The analogous reaction problem for a dipole is discussed briefly. Directions for a more realistic treatment of polar solvent effects on reaction rates are described. textcopyright 1982 American Institute of Physics.}, note = {cited By 240}, keywords = {}, pubstate = {published}, tppubtype = {article} } The influence of polar solvent dynamics in solution reactions is investigated for a simple model. In this model, a charge is subject to a chemical free energy barrier, the successful crossing of which constitutes reaction. The retarding influence of the time dependent solvent polarization is described at the continuum Debye relaxation level. The reaction rate constant k is determined as a function of the barrier curvature, the charge-solvent interaction strength, and the solvent polarization relaxation time. The reduction of k with increasingly slower solvent relaxation is found to depend sensitively on the magnitude of charge-solvent interactions. When the latter are weak, the behavior of k differs qualitatively from a standard Kramers prediction. The analogous reaction problem for a dipole is discussed briefly. Directions for a more realistic treatment of polar solvent effects on reaction rates are described. textcopyright 1982 American Institute of Physics. |
Classical Dynamics of Energy Transfer between Bonds in ABA Triatomics Article de journal E L Sibert III; W P Reinhardt; J T Hynes The Journal of Chemical Physics, 77 (7), p. 3583-3594, 1982, (cited By 197). @article{SibertIII19823583, title = {Classical Dynamics of Energy Transfer between Bonds in ABA Triatomics}, author = {E L Sibert III and W P Reinhardt and J T Hynes}, doi = {10.1063/1.444260}, year = {1982}, date = {1982-01-01}, journal = {The Journal of Chemical Physics}, volume = {77}, number = {7}, pages = {3583-3594}, abstract = {A discussion of energy transfer betwen bonds is presented for ABA triatomics for which a local mode picture affords a good zeroth-order description. A model of H2O is used to illustrate the discussion. It is shown that the energy transfer between the bonds can be readily understood both qualitatively and quantitatively in terms of the dynamics of a twofold hindered rotor. The transformation to this representation leads to a simple picture of the transition from "local mode" to "normal mode" behavior and to simple analytic expressions for the energy transfer rates. These predicted rates are found to be in excellent agreement with trajectory calculations. Isotope effects are discussed for the H2O-D 2O pair. textcopyright 1982 American Institute of Physics.}, note = {cited By 197}, keywords = {}, pubstate = {published}, tppubtype = {article} } A discussion of energy transfer betwen bonds is presented for ABA triatomics for which a local mode picture affords a good zeroth-order description. A model of H2O is used to illustrate the discussion. It is shown that the energy transfer between the bonds can be readily understood both qualitatively and quantitatively in terms of the dynamics of a twofold hindered rotor. The transformation to this representation leads to a simple picture of the transition from "local mode" to "normal mode" behavior and to simple analytic expressions for the energy transfer rates. These predicted rates are found to be in excellent agreement with trajectory calculations. Isotope effects are discussed for the H2O-D 2O pair. textcopyright 1982 American Institute of Physics. |
Quantum Mechanics of Local Mode ABA Triatomic Molecules Article de journal E L Sibert III; J T Hynes; W P Reinhardt The Journal of Chemical Physics, 77 (7), p. 3595-3604, 1982, (cited By 132). @article{SibertIII19823595, title = {Quantum Mechanics of Local Mode ABA Triatomic Molecules}, author = {E L Sibert III and J T Hynes and W P Reinhardt}, doi = {10.1063/1.444261}, year = {1982}, date = {1982-01-01}, journal = {The Journal of Chemical Physics}, volume = {77}, number = {7}, pages = {3595-3604}, abstract = {The quantum mechanics of the vibrational stretching dynamics in "local mode" triatomic molecules is examined. A model for H2O is taken as a prototype. The quantum analysis exploits the corresponding classical analysis of the companion paper, in which an approximate but accurate Hamiltonian is derived via the techniques of nonlinear mechanics. Quantization of this Hamiltonian gives H2O vibrational energies in excellent agreement with direct quantum calculations. The corresponding overtone-combination spectrum of the H2O model is analyzed in terms of local and normal mode behavior with the aid of the twofold hindered rotor perspective provided by the Hamiltonian. The splittings in the spectrum are related to the quantum dynamics of energy transfer. A semiclassical WKB analysis is also used to relate the splittings to classical energy transfer rates and quantum dynamical tunneling and reflection probabilities. textcopyright 1982 American Institute of Physics.}, note = {cited By 132}, keywords = {}, pubstate = {published}, tppubtype = {article} } The quantum mechanics of the vibrational stretching dynamics in "local mode" triatomic molecules is examined. A model for H2O is taken as a prototype. The quantum analysis exploits the corresponding classical analysis of the companion paper, in which an approximate but accurate Hamiltonian is derived via the techniques of nonlinear mechanics. Quantization of this Hamiltonian gives H2O vibrational energies in excellent agreement with direct quantum calculations. The corresponding overtone-combination spectrum of the H2O model is analyzed in terms of local and normal mode behavior with the aid of the twofold hindered rotor perspective provided by the Hamiltonian. The splittings in the spectrum are related to the quantum dynamics of energy transfer. A semiclassical WKB analysis is also used to relate the splittings to classical energy transfer rates and quantum dynamical tunneling and reflection probabilities. textcopyright 1982 American Institute of Physics. |
Local Mode Energy Transfer: Ebb and Flow Article de journal III Sibert E.L.; J S Hutchinson; W P Reinhardt; J T Hynes International Journal of Quantum Chemistry, 22 (9 S), p. 375-383, 1982, (cited By 4). @article{Sibert1982375, title = {Local Mode Energy Transfer: Ebb and Flow}, author = {III Sibert E.L. and J S Hutchinson and W P Reinhardt and J T Hynes}, doi = {10.1002/qua.560220735}, year = {1982}, date = {1982-01-01}, journal = {International Journal of Quantum Chemistry}, volume = {22}, number = {9 S}, pages = {375-383}, abstract = {The dynamics of energy transfer for local anharmonic bonds is discussed. For a model of H 2 O it is shown that energy in a single OH bond at high levels of excitation remains in that bond, that is, the OH bond is a local mode. At moderate to low levels of excitation, energy is increasingly exchanged between the two OH bonds to form (anharmonic) normal modes. An analytic model is described that gives the extent and rates of bond energy transfer. Quantization of this model yields accurate splittings in the H 2 O model's overtone-combination spectrum and their interpretation. In addition, computer results are described for the energy transfer from a vibrationally excited CH bond into an attached harmonic chain of C atoms. Possible explanations of the observed behavior are offered. Copyright textcopyright 1982 John Wiley & Sons, Inc.}, note = {cited By 4}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamics of energy transfer for local anharmonic bonds is discussed. For a model of H 2 O it is shown that energy in a single OH bond at high levels of excitation remains in that bond, that is, the OH bond is a local mode. At moderate to low levels of excitation, energy is increasingly exchanged between the two OH bonds to form (anharmonic) normal modes. An analytic model is described that gives the extent and rates of bond energy transfer. Quantization of this model yields accurate splittings in the H 2 O model's overtone-combination spectrum and their interpretation. In addition, computer results are described for the energy transfer from a vibrationally excited CH bond into an attached harmonic chain of C atoms. Possible explanations of the observed behavior are offered. Copyright textcopyright 1982 John Wiley & Sons, Inc. |
1981 |
Vibrational Energy Transfer from Highly Excited Anharmonic Oscillators. Dependence on Quantum State and Interaction Potential Article de journal D J Nesbitt; J T Hynes The Journal of Chemical Physics, 76 (12), p. 6002-6014, 1981, (cited By 75). @article{Nesbitt19816002, title = {Vibrational Energy Transfer from Highly Excited Anharmonic Oscillators. Dependence on Quantum State and Interaction Potential}, author = {D J Nesbitt and J T Hynes}, year = {1981}, date = {1981-01-01}, journal = {The Journal of Chemical Physics}, volume = {76}, number = {12}, pages = {6002-6014}, abstract = {In order to elucidate the general features of vibrational deactivation of highly excited anharmonic oscillators, we present quasiclassical trajectory calculations on prototype collinear I2 ($upsilon$)-inert gas collision systems. The results for vibrational-translational energy transfer reveal several interesting trends as a function of initial vibrational quantum state, projectile mass, and projectile-oscillator interaction potential. (1) Vibrational deactivation is inefficient from all quantum levels and for all projectile masses. The average energy transfer per collision $Delta$E is strongly peaked at intermediate vibrational levels ($upsilonapprox$80) and is observed to be at most $approx$-kbT. Further, when scaled to $hslash\omega$(E), the "local" oscillator energy spacing, $Delta$E can be accurately represented by a simple power law in vibrational quantum number over a wide range of bound states. (2) Energy transfer is progressively less efficient from levels in the neighborhood of and approaching dissociation. (3) Vibrational energy loss for high levels of initial vibrational excitation ($upsilon&$gt;90) is rather insensitive to the nature of the interaction potential. Smooth exponential and hard-sphere interaction results differ by less than an order of magnitude. This observed insensitivity motivates the development of an analytic collision model, in which simple hard-sphere geometry and dynamics are used to calculate $Delta$E. The model results are in qualitatively good agreement with trajectory calculations and also indicate that nonuniform sampling of the anharmonic oscillator velocity and phase are responsible for decreased energy transfer efficiency from high vibrational states. textcopyright 1982 American Institute of Physics.}, note = {cited By 75}, keywords = {}, pubstate = {published}, tppubtype = {article} } In order to elucidate the general features of vibrational deactivation of highly excited anharmonic oscillators, we present quasiclassical trajectory calculations on prototype collinear I2 ($upsilon$)-inert gas collision systems. The results for vibrational-translational energy transfer reveal several interesting trends as a function of initial vibrational quantum state, projectile mass, and projectile-oscillator interaction potential. (1) Vibrational deactivation is inefficient from all quantum levels and for all projectile masses. The average energy transfer per collision $Delta$E is strongly peaked at intermediate vibrational levels ($upsilonapprox$80) and is observed to be at most $approx$-kbT. Further, when scaled to $hslashømega$(E), the "local" oscillator energy spacing, $Delta$E can be accurately represented by a simple power law in vibrational quantum number over a wide range of bound states. (2) Energy transfer is progressively less efficient from levels in the neighborhood of and approaching dissociation. (3) Vibrational energy loss for high levels of initial vibrational excitation ($upsilon&$gt;90) is rather insensitive to the nature of the interaction potential. Smooth exponential and hard-sphere interaction results differ by less than an order of magnitude. This observed insensitivity motivates the development of an analytic collision model, in which simple hard-sphere geometry and dynamics are used to calculate $Delta$E. The model results are in qualitatively good agreement with trajectory calculations and also indicate that nonuniform sampling of the anharmonic oscillator velocity and phase are responsible for decreased energy transfer efficiency from high vibrational states. textcopyright 1982 American Institute of Physics. |