The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Evelyn M. Goldfield - One of the best experts on this subject based on the ideXlab platform.
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Time-dependent quantum mechanical calculations on H + O2 for Total Angular Momentum J>0: Comparing different dynamical approximations
Physical Chemistry Chemical Physics, 2001Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H + O2 → OH + O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J>0 using three different approximations: the J-shifting approximation, the helicity conserving approximation, and the truncated basis approximation. Both reaction probabilities and reaction cross sections are calculated and compared to recent rigorous close coupling calculations (E. M. Goldfield and A. J. H. M. Meijer, J. Chem. Phys., 2000, 113, 11055). Our results show significant deviations from the close coupling reaction probabilities for all approximations studied. As a result the approximate cross sections do not agree very well with the close coupling cross sections. We also compare our results to an approximate J-shifting type method due to Varandas (A. J. C. Varandas, Mol. Phys., 1995, 85, 1159). Our comparisons show the deficiencies of the different approximate methods for this reaction and emphasize the need to perform rigorous calculations.
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time dependent quantum mechanical calculations on h o2 for Total Angular Momentum j 0 comparing different dynamical approximations
Physical Chemistry Chemical Physics, 2001Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H + O2 → OH + O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J>0 using three different approximations: the J-shifting approximation, the helicity conserving approximation, and the truncated basis approximation. Both reaction probabilities and reaction cross sections are calculated and compared to recent rigorous close coupling calculations (E. M. Goldfield and A. J. H. M. Meijer, J. Chem. Phys., 2000, 113, 11055). Our results show significant deviations from the close coupling reaction probabilities for all approximations studied. As a result the approximate cross sections do not agree very well with the close coupling cross sections. We also compare our results to an approximate J-shifting type method due to Varandas (A. J. C. Varandas, Mol. Phys., 1995, 85, 1159). Our comparisons show the deficiencies of the different approximate methods for this reaction and emphasize the need to perform rigorous calculations.
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Time-dependent quantum mechanical calculations on H+O2 for Total Angular Momentum J>0. III. Total cross sections
The Journal of Chemical Physics, 2000Co-Authors: Evelyn M. Goldfield, Anthony J. H. M. MeijerAbstract:The H+O2→OH+O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J=15, 20, 25, 35. This work is a continuation of previous studies for J⩽10. The calculations were performed combining a real wave packet method with the Coriolis coupled method on parallel computers. We find that for most energies there is a monotonic decrease of reaction probability with increasing J. Nevertheless, due to the 2J+1 degeneracy, higher Angular Momentum states contribute significantly to the Total reaction cross section. A smoothing/interpolation/extrapolation scheme is employed to compute Total reaction cross sections. These cross sections are compared with quasiclassical results on the same potential energy surface, and the most recent experimental cross sections. Comparisons with quasiclassical results show the significance of zero-point energy constraints. The quantum mechanical theoretical cross sections are smaller than the experimental ones everywhere, suggesting that a more acc...
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Time-dependent quantum mechanical calculations on H+O2 for Total Angular Momentum J>0 II: On the importance of Coriolis coupling
The Journal of Chemical Physics, 1999Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H+O2→OH+O reaction has been studied for Total Angular Momentum J>0 with a time-dependent wave packet method using the Coriolis coupled method of Goldfield and Gray [E. M. Goldfield and S. K. Gray, Comp. Phys. Commun. 98, 1 (1996)] on parallel computers. Helicity conserving (HC) and coupled channel (CC) calculations were performed for J=1, J=2, J=5, and J=10 using two different embeddings for the body fixed coordinate system to investigate the importance of Coriolis coupling for this reactive system. If the H–O2 distance is taken to be the z axis of the coordinate system, we find poor agreement between the HC and the CC calculations for J>2. When the O2 bond is taken to be the z axis, we find good agreement between the CC and HC calculations at low J. For higher J the agreement gets progressively worse, especially at higher energies. We can explain these results using a classical model from a previous paper on H+O2 [A. J. H. M. Meijer and E. M. Goldfield, J. Chem. Phys. 108, 5404 (1998)].
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Time-dependent quantum mechanical calculations on H+O2 for Total Angular Momentum J>0
The Journal of Chemical Physics, 1998Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H+O2→OH+O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J=0, 1, 2, and 5, using the Coriolis coupled method [E. M. Goldfield and S. K. Gray, Comp. Phys. Commun. 98, 1 (1996)] on parallel computers. We find that at higher energies the Total reaction probability decreases by a factor of 2 in going from a J=0 calculation to a J=1 calculation. The effect for higher J with respect to J=1 is less dramatic. We investigated the decrease in reaction probability for J>0 by examining the different initial conditions with respect to Ω, the projection of J onto the body-fixed z axis for the J>0 calculations. We conclude that the reaction probability is a strong function of Ω. If Ω=0 for J>0, collision geometries are accessible that lead to an enhanced reaction probability.
William F. Polik - One of the best experts on this subject based on the ideXlab platform.
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A random matrix/transition state theory for the probability distribution of state-specific unimolecular decay rates : generalization to include Total Angular Momentum conservation and other dynamical symmetries
The Journal of Chemical Physics, 1993Co-Authors: Rigoberto Hernandez, William H. Miller, C. Bradley Moore, William F. PolikAbstract:A previously developed random matrix/transition state theory (RM/TST) model for the probability distribution of state‐specific unimolecular decay rates has been generalized to incorporate Total Angular Momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall theory gives a good description of the state‐specific rates for the D2CO→D2+CO unimolecular decay; in particular, it describes the dependence of the distribution of rates on Total Angular Momentum J. Comparison of the experimental values with results of the RM/TST theory suggests that there is mixing among the rovibrational states.
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a random matrix transition state theory for the probability distribution of state specific unimolecular decay rates generalization to include Total Angular Momentum conservation and other dynamical symmetries
Journal of Chemical Physics, 1993Co-Authors: Rigoberto Hernandez, William H. Miller, Bradley C Moore, William F. PolikAbstract:A previously developed random matrix/transition state theory (RM/TST) model for the probability distribution of state‐specific unimolecular decay rates has been generalized to incorporate Total Angular Momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall theory gives a good description of the state‐specific rates for the D2CO→D2+CO unimolecular decay; in particular, it describes the dependence of the distribution of rates on Total Angular Momentum J. Comparison of the experimental values with results of the RM/TST theory suggests that there is mixing among the rovibrational states.
William H. Miller - One of the best experts on this subject based on the ideXlab platform.
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quantum mechanical rate constants for o oh h o2 for Total Angular Momentum j 0
Journal of Physical Chemistry A, 1998Co-Authors: David Skinner, Timothy C. Germann, William H. MillerAbstract:Thermal rate constants have been calculated for the titled reaction for Total Angular Momentum J > 0 using the quantum flux correlation function methodology of Thompson and Miller [Thompson, W. H.;...
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Quantum Mechanical Rate Constants for O + OH ⇌ H + O2 for Total Angular Momentum J > 0
The Journal of Physical Chemistry A, 1998Co-Authors: David Skinner, Timothy C. Germann, William H. MillerAbstract:Thermal rate constants have been calculated for the titled reaction for Total Angular Momentum J > 0 using the quantum flux correlation function methodology of Thompson and Miller [Thompson, W. H.;...
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A random matrix/transition state theory for the probability distribution of state-specific unimolecular decay rates : generalization to include Total Angular Momentum conservation and other dynamical symmetries
The Journal of Chemical Physics, 1993Co-Authors: Rigoberto Hernandez, William H. Miller, C. Bradley Moore, William F. PolikAbstract:A previously developed random matrix/transition state theory (RM/TST) model for the probability distribution of state‐specific unimolecular decay rates has been generalized to incorporate Total Angular Momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall theory gives a good description of the state‐specific rates for the D2CO→D2+CO unimolecular decay; in particular, it describes the dependence of the distribution of rates on Total Angular Momentum J. Comparison of the experimental values with results of the RM/TST theory suggests that there is mixing among the rovibrational states.
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a random matrix transition state theory for the probability distribution of state specific unimolecular decay rates generalization to include Total Angular Momentum conservation and other dynamical symmetries
Journal of Chemical Physics, 1993Co-Authors: Rigoberto Hernandez, William H. Miller, Bradley C Moore, William F. PolikAbstract:A previously developed random matrix/transition state theory (RM/TST) model for the probability distribution of state‐specific unimolecular decay rates has been generalized to incorporate Total Angular Momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall theory gives a good description of the state‐specific rates for the D2CO→D2+CO unimolecular decay; in particular, it describes the dependence of the distribution of rates on Total Angular Momentum J. Comparison of the experimental values with results of the RM/TST theory suggests that there is mixing among the rovibrational states.
Rigoberto Hernandez - One of the best experts on this subject based on the ideXlab platform.
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A random matrix/transition state theory for the probability distribution of state-specific unimolecular decay rates : generalization to include Total Angular Momentum conservation and other dynamical symmetries
The Journal of Chemical Physics, 1993Co-Authors: Rigoberto Hernandez, William H. Miller, C. Bradley Moore, William F. PolikAbstract:A previously developed random matrix/transition state theory (RM/TST) model for the probability distribution of state‐specific unimolecular decay rates has been generalized to incorporate Total Angular Momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall theory gives a good description of the state‐specific rates for the D2CO→D2+CO unimolecular decay; in particular, it describes the dependence of the distribution of rates on Total Angular Momentum J. Comparison of the experimental values with results of the RM/TST theory suggests that there is mixing among the rovibrational states.
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a random matrix transition state theory for the probability distribution of state specific unimolecular decay rates generalization to include Total Angular Momentum conservation and other dynamical symmetries
Journal of Chemical Physics, 1993Co-Authors: Rigoberto Hernandez, William H. Miller, Bradley C Moore, William F. PolikAbstract:A previously developed random matrix/transition state theory (RM/TST) model for the probability distribution of state‐specific unimolecular decay rates has been generalized to incorporate Total Angular Momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall theory gives a good description of the state‐specific rates for the D2CO→D2+CO unimolecular decay; in particular, it describes the dependence of the distribution of rates on Total Angular Momentum J. Comparison of the experimental values with results of the RM/TST theory suggests that there is mixing among the rovibrational states.
Anthony J. H. M. Meijer - One of the best experts on this subject based on the ideXlab platform.
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time dependent quantum mechanical calculations on h o2 for Total Angular Momentum j 0 comparing different dynamical approximations
Physical Chemistry Chemical Physics, 2001Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H + O2 → OH + O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J>0 using three different approximations: the J-shifting approximation, the helicity conserving approximation, and the truncated basis approximation. Both reaction probabilities and reaction cross sections are calculated and compared to recent rigorous close coupling calculations (E. M. Goldfield and A. J. H. M. Meijer, J. Chem. Phys., 2000, 113, 11055). Our results show significant deviations from the close coupling reaction probabilities for all approximations studied. As a result the approximate cross sections do not agree very well with the close coupling cross sections. We also compare our results to an approximate J-shifting type method due to Varandas (A. J. C. Varandas, Mol. Phys., 1995, 85, 1159). Our comparisons show the deficiencies of the different approximate methods for this reaction and emphasize the need to perform rigorous calculations.
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Time-dependent quantum mechanical calculations on H + O2 for Total Angular Momentum J>0: Comparing different dynamical approximations
Physical Chemistry Chemical Physics, 2001Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H + O2 → OH + O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J>0 using three different approximations: the J-shifting approximation, the helicity conserving approximation, and the truncated basis approximation. Both reaction probabilities and reaction cross sections are calculated and compared to recent rigorous close coupling calculations (E. M. Goldfield and A. J. H. M. Meijer, J. Chem. Phys., 2000, 113, 11055). Our results show significant deviations from the close coupling reaction probabilities for all approximations studied. As a result the approximate cross sections do not agree very well with the close coupling cross sections. We also compare our results to an approximate J-shifting type method due to Varandas (A. J. C. Varandas, Mol. Phys., 1995, 85, 1159). Our comparisons show the deficiencies of the different approximate methods for this reaction and emphasize the need to perform rigorous calculations.
-
Time-dependent quantum mechanical calculations on H+O2 for Total Angular Momentum J>0. III. Total cross sections
The Journal of Chemical Physics, 2000Co-Authors: Evelyn M. Goldfield, Anthony J. H. M. MeijerAbstract:The H+O2→OH+O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J=15, 20, 25, 35. This work is a continuation of previous studies for J⩽10. The calculations were performed combining a real wave packet method with the Coriolis coupled method on parallel computers. We find that for most energies there is a monotonic decrease of reaction probability with increasing J. Nevertheless, due to the 2J+1 degeneracy, higher Angular Momentum states contribute significantly to the Total reaction cross section. A smoothing/interpolation/extrapolation scheme is employed to compute Total reaction cross sections. These cross sections are compared with quasiclassical results on the same potential energy surface, and the most recent experimental cross sections. Comparisons with quasiclassical results show the significance of zero-point energy constraints. The quantum mechanical theoretical cross sections are smaller than the experimental ones everywhere, suggesting that a more acc...
-
Time-dependent quantum mechanical calculations on H+O2 for Total Angular Momentum J>0 II: On the importance of Coriolis coupling
The Journal of Chemical Physics, 1999Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H+O2→OH+O reaction has been studied for Total Angular Momentum J>0 with a time-dependent wave packet method using the Coriolis coupled method of Goldfield and Gray [E. M. Goldfield and S. K. Gray, Comp. Phys. Commun. 98, 1 (1996)] on parallel computers. Helicity conserving (HC) and coupled channel (CC) calculations were performed for J=1, J=2, J=5, and J=10 using two different embeddings for the body fixed coordinate system to investigate the importance of Coriolis coupling for this reactive system. If the H–O2 distance is taken to be the z axis of the coordinate system, we find poor agreement between the HC and the CC calculations for J>2. When the O2 bond is taken to be the z axis, we find good agreement between the CC and HC calculations at low J. For higher J the agreement gets progressively worse, especially at higher energies. We can explain these results using a classical model from a previous paper on H+O2 [A. J. H. M. Meijer and E. M. Goldfield, J. Chem. Phys. 108, 5404 (1998)].
-
Time-dependent quantum mechanical calculations on H+O2 for Total Angular Momentum J>0
The Journal of Chemical Physics, 1998Co-Authors: Anthony J. H. M. Meijer, Evelyn M. GoldfieldAbstract:The H+O2→OH+O reaction has been studied with a time-dependent wave packet method for Total Angular Momentum J=0, 1, 2, and 5, using the Coriolis coupled method [E. M. Goldfield and S. K. Gray, Comp. Phys. Commun. 98, 1 (1996)] on parallel computers. We find that at higher energies the Total reaction probability decreases by a factor of 2 in going from a J=0 calculation to a J=1 calculation. The effect for higher J with respect to J=1 is less dramatic. We investigated the decrease in reaction probability for J>0 by examining the different initial conditions with respect to Ω, the projection of J onto the body-fixed z axis for the J>0 calculations. We conclude that the reaction probability is a strong function of Ω. If Ω=0 for J>0, collision geometries are accessible that lead to an enhanced reaction probability.
