The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Keisaku Ishii - One of the best experts on this subject based on the ideXlab platform.
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An ab initio molecular dynamics study on the dissociative Recombination Reaction of HD2O+ + e−
Theoretical Chemistry Accounts, 2008Co-Authors: Megumi Kayanuma, Tetsuya Taketsugu, Keisaku IshiiAbstract:An ab initio molecular dynamics simulations have been carried out for the dissociative Recombination Reaction of the deuterium-substituted hydronium cation, HD2O+ + e−, at the state-averaged multiconfigurational self-consistent field level. In the present simulations, five electronic states of HD2O were included explicitly, and nonadiabatic transitions among adiabatic electronic states were taken into account by the Tully’s fewest switches algorithm. It is shown that the dominant products, OD + D + H, were generated in 63% of trajectories, while the products, OH + 2D, were generated in only 11% of trajectories, indicating that the release of a light fragment H is favored over the release of a heavy fragment D. This result is in conformity with the observation that there is a larger amount of deuterium substituted species than the non-substituted species in the interstellar space.
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An ab initio molecular dynamics study on the dissociative Recombination Reaction of HD2O+ + e−
Theoretical Chemistry Accounts, 2007Co-Authors: Megumi Kayanuma, Tetsuya Taketsugu, Keisaku IshiiAbstract:An ab initio molecular dynamics simulations have been carried out for the dissociative Recombination Reaction of the deuterium-substituted hydronium cation, HD2O+ + e(-), at the state-averaged multiconfigurational self-consistent field level. In the present simulations, five electronic states of HD2O were included explicitly, and non-adiabatic transitions among adiabatic electronic states were taken into account by the Tully's fewest switches algorithm. It is shown that the dominant products, OD + D + H, were generated in 63% of trajectories, while the products, OH + 2D, were generated in only 11% of trajectories, indicating that the release of a light fragment H is favored over the release of a heavy fragment D. This result is in conformity with the observation that there is a larger amount of deuterium substituted species than the non-substituted species in the interstellar space
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Theoretical Elucidation of the Unusually High [HNC]/[HCN] Abundance Ratio in Interstellar Space: Two-dimensional and Two-State Quantum Wave Packet Dynamics Study on the Branching Ratio of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN +
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
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theoretical elucidation of the unusually high hnc hcn abundance ratio in interstellar space two dimensional and two state quantum wave packet dynamics study on the branching ratio of the dissociative Recombination Reaction hcnh e hnc hcn h
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
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Ab Initio Direct Trajectory Simulation with Nonadiabatic Transitions of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN + H
The Astrophysical Journal, 2004Co-Authors: Tetsuya Taketsugu, Keisaku Ishii, Asami Tajima, Tsuneo HiranoAbstract:The dissociative Recombination Reaction of HCNH+ + e- via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2Π, 1 2Σ+, and 2 2Σ+, were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this Reaction, supporting the picture that HCNH+ plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
Koichi Yamashita - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Elucidation of the Unusually High [HNC]/[HCN] Abundance Ratio in Interstellar Space: Two-dimensional and Two-State Quantum Wave Packet Dynamics Study on the Branching Ratio of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN +
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
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theoretical elucidation of the unusually high hnc hcn abundance ratio in interstellar space two dimensional and two state quantum wave packet dynamics study on the branching ratio of the dissociative Recombination Reaction hcnh e hnc hcn h
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
Tetsuya Taketsugu - One of the best experts on this subject based on the ideXlab platform.
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An ab initio molecular dynamics study on the dissociative Recombination Reaction of HD2O+ + e−
Theoretical Chemistry Accounts, 2008Co-Authors: Megumi Kayanuma, Tetsuya Taketsugu, Keisaku IshiiAbstract:An ab initio molecular dynamics simulations have been carried out for the dissociative Recombination Reaction of the deuterium-substituted hydronium cation, HD2O+ + e−, at the state-averaged multiconfigurational self-consistent field level. In the present simulations, five electronic states of HD2O were included explicitly, and nonadiabatic transitions among adiabatic electronic states were taken into account by the Tully’s fewest switches algorithm. It is shown that the dominant products, OD + D + H, were generated in 63% of trajectories, while the products, OH + 2D, were generated in only 11% of trajectories, indicating that the release of a light fragment H is favored over the release of a heavy fragment D. This result is in conformity with the observation that there is a larger amount of deuterium substituted species than the non-substituted species in the interstellar space.
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An ab initio molecular dynamics study on the dissociative Recombination Reaction of HD2O+ + e−
Theoretical Chemistry Accounts, 2007Co-Authors: Megumi Kayanuma, Tetsuya Taketsugu, Keisaku IshiiAbstract:An ab initio molecular dynamics simulations have been carried out for the dissociative Recombination Reaction of the deuterium-substituted hydronium cation, HD2O+ + e(-), at the state-averaged multiconfigurational self-consistent field level. In the present simulations, five electronic states of HD2O were included explicitly, and non-adiabatic transitions among adiabatic electronic states were taken into account by the Tully's fewest switches algorithm. It is shown that the dominant products, OD + D + H, were generated in 63% of trajectories, while the products, OH + 2D, were generated in only 11% of trajectories, indicating that the release of a light fragment H is favored over the release of a heavy fragment D. This result is in conformity with the observation that there is a larger amount of deuterium substituted species than the non-substituted species in the interstellar space
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Theoretical Elucidation of the Unusually High [HNC]/[HCN] Abundance Ratio in Interstellar Space: Two-dimensional and Two-State Quantum Wave Packet Dynamics Study on the Branching Ratio of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN +
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
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theoretical elucidation of the unusually high hnc hcn abundance ratio in interstellar space two dimensional and two state quantum wave packet dynamics study on the branching ratio of the dissociative Recombination Reaction hcnh e hnc hcn h
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
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Ab Initio Direct Trajectory Simulation with Nonadiabatic Transitions of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN + H
The Astrophysical Journal, 2004Co-Authors: Tetsuya Taketsugu, Keisaku Ishii, Asami Tajima, Tsuneo HiranoAbstract:The dissociative Recombination Reaction of HCNH+ + e- via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2Π, 1 2Σ+, and 2 2Σ+, were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this Reaction, supporting the picture that HCNH+ plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
Asami Tajima - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Elucidation of the Unusually High [HNC]/[HCN] Abundance Ratio in Interstellar Space: Two-dimensional and Two-State Quantum Wave Packet Dynamics Study on the Branching Ratio of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN +
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
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theoretical elucidation of the unusually high hnc hcn abundance ratio in interstellar space two dimensional and two state quantum wave packet dynamics study on the branching ratio of the dissociative Recombination Reaction hcnh e hnc hcn h
The Astrophysical Journal, 2006Co-Authors: Keisaku Ishii, Asami Tajima, Tetsuya Taketsugu, Koichi YamashitaAbstract:In order to elucidate the unusually high [HNC]/[HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative Recombination Reaction HCNH+ + e- → HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 2Σ+ and 2 2Σ+. Two adiabatic PESs of 1 2Σ+ and 2 2Σ+ have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2 2Σ+ adiabatic PES. The resulting branching ratios of [HNC]/[HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
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Ab Initio Direct Trajectory Simulation with Nonadiabatic Transitions of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN + H
The Astrophysical Journal, 2004Co-Authors: Tetsuya Taketsugu, Keisaku Ishii, Asami Tajima, Tsuneo HiranoAbstract:The dissociative Recombination Reaction of HCNH+ + e- via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2Π, 1 2Σ+, and 2 2Σ+, were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this Reaction, supporting the picture that HCNH+ plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
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ab initio direct trajectory simulation with nonadiabatic transitions of the dissociative Recombination Reaction hcnh e hnc hcn h
The Astrophysical Journal, 2004Co-Authors: Tetsuya Taketsugu, Keisaku Ishii, Asami Tajima, Tsuneo HiranoAbstract:The dissociative Recombination Reaction of HCNH+ + e- via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2Π, 1 2Σ+, and 2 2Σ+, were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this Reaction, supporting the picture that HCNH+ plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
Tsuneo Hirano - One of the best experts on this subject based on the ideXlab platform.
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Ab Initio Direct Trajectory Simulation with Nonadiabatic Transitions of the Dissociative Recombination Reaction HCNH+ + e– → HNC/HCN + H
The Astrophysical Journal, 2004Co-Authors: Tetsuya Taketsugu, Keisaku Ishii, Asami Tajima, Tsuneo HiranoAbstract:The dissociative Recombination Reaction of HCNH+ + e- via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2Π, 1 2Σ+, and 2 2Σ+, were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this Reaction, supporting the picture that HCNH+ plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
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ab initio direct trajectory simulation with nonadiabatic transitions of the dissociative Recombination Reaction hcnh e hnc hcn h
The Astrophysical Journal, 2004Co-Authors: Tetsuya Taketsugu, Keisaku Ishii, Asami Tajima, Tsuneo HiranoAbstract:The dissociative Recombination Reaction of HCNH+ + e- via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2Π, 1 2Σ+, and 2 2Σ+, were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this Reaction, supporting the picture that HCNH+ plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
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potential energy surfaces and branching ratio of the dissociative Recombination Reaction hcnh e an ab initio molecular orbital study
Journal of Chemical Physics, 1998Co-Authors: Yoko Shiba, Tsuneo Hirano, Umpei Nagashima, Keisaku IshiiAbstract:Two-dimensional potential energy surfaces for the dissociative Recombination Reaction, HCNH++e− → (HCNH)* → HNC/HCN+H, have been calculated by the CASSCF-MRSDCI ab initio molecular orbital method. Near the HCNH+ ground state surface, which represents the upper limit of neutral HCNH Rydberg state surfaces, only two dissociative valence states of HCNH are located. One is the 2Σ+ state resulting in H–C bond dissociation to produce HNC, and the other is the 2Σ+ state resulting in H–N bond dissociation to produce HCN. The seam of intersection of these two potential surfaces almost bisects the zero-point vibrational wave function of the Rydberg-limit state of the neutral HCNH species, indicating that, through descending Rydberg ladder, transition from the Rydberg-limit state to each dissociative surface occurs with almost the same probability. Thus, branching ratio to HNC and HCN is predicted to be of the order of one or slightly higher, explaining the thermochemically unrealistic interstellar HNC/HCN abundance...
