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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.
Leif Holmlid - One of the best experts on this subject based on the ideXlab platform.
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rydberg matter as the diffuse Interstellar band dib carrier in Interstellar Space the model and accurate calculations of band centres
Physical Chemistry Chemical Physics, 2004Co-Authors: Leif HolmlidAbstract:A model for the interpretation of a large number of the 280 diffuse Interstellar bands (DIBs) is presented. The bands are proposed to be due to electronic excitation processes in Rydberg Matter leading to doubly excited coplanar Rydberg molecules. Rydberg Matter is composed of atoms and small molecules like H2 in condensed coherent circular Rydberg states. It has been studied in the laboratory especially with laser time-of-flight experiments and in laser Raman spectroscopy studies. Rydberg Matter is used as the lasing medium in an ultra wide-band tunable IR laser (Chem. Phys. Lett. 376 (2003) 812). Rydberg Matter has recently been proposed to be part of the dark matter in the Universe, to be the source of the so called UIR emission bands from Interstellar Space and to give rise to the Faraday rotation in intergalactic Space. The potential energy of the doubly excited coplanar Rydberg states, which are the final states in the DIB transitions, is now calculated accurately in the classical limit. More than 60 of the DIB bands are calculated with good accuracy. The intensity distributions of the transitions are relatively smooth without unexplained missing bands. The model used does not predict too many bands. The calculations are very accurate, in this optimal wavelength region, relative to other calculations in systems of a complexity comparable to Rydberg Matter.
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a novel model for the interpretation of the unidentified infrared uir bands from Interstellar Space deexcitation of rydberg matter
Astronomy and Astrophysics, 2000Co-Authors: Leif HolmlidAbstract:The so called unidentified infrared (UIR) emission bands, observed from Interstellar Space for more than 25 years, are presently believed to be due to carbonaceous material in some form, for example polycyclic aromatic hydrocarbons (PAHs). However, the evidence is based on absorption data, which clearly is not adequate due to differences in the pro- cesses, for example the thermal factor. It also seems doubtful that enough carbon is available to form all the required PAHs, and that the vapor pressure is high enough to keep almost all such molecules in the gas phase. We now report on a model in which all UIR bands are due to electronic deexcitation in the condensed phase named Rydberg Matter. This type of very low- density condensed matter is formed by condensation of Rydberg states of almost any type of atom or small molecule, in Space mainly hydrogen atoms and molecules. The intial formation of Rydberg states is due to desorption of alkali atoms from surfaces of small particles, especially carbon particles. This desorption can be caused by radiation or moderate heat and gives long- lived circular Rydberg states. Rydberg Matter can be produced in macroscopic quantities in the laboratory. There is no lower gas density limit for its formation. All the reported UIR peaks from different objects fall within the bands for deexcitation from Ryd- berg Matter states with principal quantum numbersn = 40-200. Most of the transitions are two-electron deexcitation processes, but also one-electron capture processes are identified. The UIR spectra of type sA-Dc anb eunderstood within this model. The agreement with observations is better for the Rydberg Mat- ter model, with small a priori information content, than for the current PAH model.
Keisaku Ishii - 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.
R. De La Fuente Marcos - One of the best experts on this subject based on the ideXlab platform.
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comet c 2018 v1 machholz fujikawa iwamoto dislodged from the oort cloud or coming from Interstellar Space
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: C. De La Fuente Marcos, R. De La Fuente MarcosAbstract:The chance discovery of the first Interstellar minor body, 1I/2017 U1 (`Oumuamua), indicates that we may have been visited by such objects in the past and that these events may repeat in the future. Unfortunately, minor bodies following nearly parabolic or hyperbolic paths tend to receive little attention: over 3/4 of those known have data-arcs shorter than 30 d and, consistently, rather uncertain orbit determinations. This fact suggests that we may have observed Interstellar interlopers in the past, but failed to recognize them as such due to insufficient data. Early identification of promising candidates by using N-body simulations may help in improving this situation, triggering follow-up observations before they leave the Solar system. Here, we use this technique to investigate the pre- and post-perihelion dynamical evolution of the slightly hyperbolic comet C/2018 V1 (Machholz-Fujikawa-Iwamoto) to understand its origin and relevance within the context of known parabolic and hyperbolic minor bodies. Based on the available data, our calculations suggest that although C/2018 V1 may be a former member of the Oort Cloud, an origin beyond the Solar system cannot be excluded. If extrasolar, it might have entered the Solar system from Interstellar Space at low relative velocity with respect to the Sun. The practical feasibility of this alternative scenario has been assessed within the kinematic context of the stellar neighbourhood of the Sun, using data from Gaia second data release, and two robust solar sibling candidates have been identified. Our results suggest that comets coming from Interstellar Space at low heliocentric velocities may not be rare.
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Comet C/2018 V1 (Machholz–Fujikawa–Iwamoto): dislodged from the Oort Cloud or coming from Interstellar Space?
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: C. De La Fuente Marcos, R. De La Fuente MarcosAbstract:The chance discovery of the first Interstellar minor body, 1I/2017 U1 (`Oumuamua), indicates that we may have been visited by such objects in the past and that these events may repeat in the future. Unfortunately, minor bodies following nearly parabolic or hyperbolic paths tend to receive little attention: over 3/4 of those known have data-arcs shorter than 30 d and, consistently, rather uncertain orbit determinations. This fact suggests that we may have observed Interstellar interlopers in the past, but failed to recognize them as such due to insufficient data. Early identification of promising candidates by using N-body simulations may help in improving this situation, triggering follow-up observations before they leave the Solar system. Here, we use this technique to investigate the pre- and post-perihelion dynamical evolution of the slightly hyperbolic comet C/2018 V1 (Machholz-Fujikawa-Iwamoto) to understand its origin and relevance within the context of known parabolic and hyperbolic minor bodies. Based on the available data, our calculations suggest that although C/2018 V1 may be a former member of the Oort Cloud, an origin beyond the Solar system cannot be excluded. If extrasolar, it might have entered the Solar system from Interstellar Space at low relative velocity with respect to the Sun. The practical feasibility of this alternative scenario has been assessed within the kinematic context of the stellar neighbourhood of the Sun, using data from Gaia second data release, and two robust solar sibling candidates have been identified. Our results suggest that comets coming from Interstellar Space at low heliocentric velocities may not be rare.
Tetsuya Taketsugu - 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.
