The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Clément Buvat - One of the best experts on this subject based on the ideXlab platform.
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A fully nonlinear implicit model for wave interactions with submerged structures in forced or free Motion
Engineering Analysis with Boundary Elements, 2012Co-Authors: Etienne Guerber, Michel Benoit, Stephan T. Grilli, Clément BuvatAbstract:Abstract The purpose of this work is to develop advanced numerical tools for modeling two-way fully nonlinear interactions of ocean surface waves (irregular waves in the general situation) with submerged structures undergoing Large Amplitude Motion, that could represent Wave Energy Converters (WECs). In our modeling approach, an existing two-dimensional Numerical Wave Tank (NWT), based on potential flow theory, is extended to include a submerged horizontal cylinder of arbitrary cross-section. The mathematical problem and related numerical solution are first introduced. Then, conservation of volume and conservation of energy are checked, respectively, in the case of a circular cylinder in a prescribed Large Amplitude Motion and in the case of a circular cylinder in a free Motion. Interactions between waves and a submerged circular cylinder computed by the model are then compared to mathematical solutions for two situations: a cylinder in prescribed Motion and a freely moving cylinder.
L. H. Coudert - One of the best experts on this subject based on the ideXlab platform.
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the first astrophysical detection terahertz spectrum and database for the monodeuterated species of methyl formate hcooch2d
The Astrophysical Journal, 2013Co-Authors: L. H. Coudert, Brian J Drouin, B Tercero, J Cernicharo, Jeanclaude Guillemin, R A Motiyenko, L MargulesAbstract:Based on new measurements carried out in the laboratory from 0.77 to 1.2 THz and on a line-frequency analysis of these new data, along with previously published data, we build a line list for HCOOCH2D that leads to its first detection in the Orion KL nebula. The observed lines, both in space and in the laboratory, involve the cis D-in-plane and trans D-out-of-plane conformations of HCOOCH2D and the two tunneling states arising from the Large-Amplitude Motion connecting the two trans configurations. The model used in the line position calculation accounts for both cis and trans conformations, as well as the Large-Amplitude Motion.
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The first astrophysical detection, tetrahertz spectrum, and database for the monodeuterated species of methyl formate HCOOCH2D
The Astrophysical Journal, 2013Co-Authors: L. H. Coudert, Brian J Drouin, B Tercero, J Cernicharo, Jeanclaude Guillemin, R A Motiyenko, L MargulesAbstract:Based on new measurements carried out in the laboratory from 0.77 to 1.2 THz and on a line-frequency analysis of these new data, along with previously published data, we build a line list for HCOOCH2D that leads to its first detection in the Orion KL nebula. The observed lines, both in space and in the laboratory, involve the cis D-in-plane and trans D-out-of-plane conformations of HCOOCH2D and the two tunneling states arising from the Large-Amplitude Motion connecting the two trans configurations. The model used in the line position calculation accounts for both cis and trans conformations, as well as the Large-Amplitude Motion.
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Ab initio and experimental studies of the Large-Amplitude Motion in BF2OH.
The journal of physical chemistry. A, 2008Co-Authors: L. H. Coudert, Pablo García-fernández, Heinrich Mäder, Jean Demaison, James E. BoggsAbstract:The ground state rotational spectrum of BF2OH was measured under high resolution by microwave Fourier transform spectroscopy (FTMW), and the small torsional splitting could be resolved for several lines. This splitting was analyzed using a phenomenological model previously developed for HNO3 [Coudert and Perrin, J. Mol. Spectrosc. 1995, 172, 352] and with the help of the geometries of the stationary points calculated ab initio. The torsional splitting was also calculated using the results of the calculations for the ground vibrational state, for the excited OH torsional states 91 and 92, and for the excited BOH bending state 41, and a satisfactory agreement with available experimental data was found.
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Microwave spectrum, tunneling Motions, and quadrupole coupling hyperfine structure of ethylene diamine
Journal of Molecular Spectroscopy, 2006Co-Authors: I. Merke, L. H. CoudertAbstract:Abstract New transitions are measured in the microwave spectrum of two conformers of the non-rigid ethylene diamine (CH 2 NH 2 –CH 2 NH 2 ) molecule using both molecular beam Fourier transform and stark modulation spectroscopy. Ab initio calculations are carried out to obtain geometries and energies for several stationary points of the potential energy surface and to gain quantitative information on the tunneling paths along which the molecule tunnels. The microwave data are reproduced using an IAM-like approach which accounts for the rotational dependence of the tunneling splitting corresponding to the interconversion Large Amplitude Motion. For one of the conformers, the results of this analysis are consistent with the ones obtained through ab initio calculations. Hyperfine patterns are analyzed with the help of a theoretical approach accounting for the Large Amplitude Motion effects and for hyperfine matrix elements within and between tunneling sublevels.
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Analysis of the Rotational Levels of SiC2
Journal of Molecular Spectroscopy, 1993Co-Authors: L. H. CoudertAbstract:Abstract In the T-shaped SiC2 molecule, there is experimental evidence that the C2 fragment is bound to the silicium atom by an ionic essentially nondirectional bond, and thus can rotate within the molecule. The ν3 mode, corresponding to this internal rotation, is, therefore, a Large-Amplitude Motion. In an attempt to calculate the rovibrational energy levels of the SiC2 molecule, a formalism is derived in which this ν3 mode is treated as a Large-Amplitude Motion. In this formalism, the strong dependence of the inverse moment of inertia tensor on the angle of internal rotation, the Coriolis coupling between the Large Amplitude Motion and the overall rotation, and the potential barrier hindering the internal rotation are accounted for. This formalism is used to carry out analyses of the microwave data of SiC2 within the ground vibrational state and within the first excited vibrational state of the ν3 mode, v3 = 1. For both vibrational states, which are fitted separately, more satisfactory results are obtained than with a standard Watson-type Hamiltonian.
Kazuo Takatsuka - One of the best experts on this subject based on the ideXlab platform.
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Expected significance of weakly chaotic vibrational Motions in single molecule spectroscopy
The Journal of Chemical Physics, 1995Co-Authors: Naoyuki Hashimoto, Kazuo TakatsukaAbstract:It is known that a new kind of Large Amplitude Motion gives rise to as a very characteristic mode of weak chaos. This is essentially an unpredictable and intermittent Motion taking place in a thin quasiseparatrix which wanders among several very clear vibrational modes. In this paper, we study the spectroscopic characterization of the quantum version of this Large Amplitude Motion in terms of the dynamics of a wave packet, which is prepared in a narrow energy‐range so that it is localized along a thin quasiseparatrix. In particular, we discuss possible significance of the weak chaos in single molecule spectroscopy, for which the spectra are supposed to be averaged neither in ensemble of molecules nor in time. That this wavepacket state is unusual originates from the extremely long‐time behavior and the strong sensitivity to the initial condition at which the wave packet is prepared. The weak chaos combined with the statistical nature of quantum mechanics brings about a notion of unreproducibility in the spectrum. Conversely, it is anticipated that one of the distinguished features inherent to a single molecule spectroscopy manifests itself when weak chaos is observed.
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Concept of phase-space Large-Amplitude Motion. A classical study
Chemical Physics Letters, 1993Co-Authors: Kazuo TakatsukaAbstract:Abstract We present a new concept of Large-Amplitude Motion for molecular vibrations called phase-space Large-Amplitude Motion (PSLAM), which is an outcome of a study of Hamiltonian chaos. The time-dependent behavior of PSLAM is shown to be extremely irregular and unpredictable. PSLAM is anticipated to be identified in experimental observations.
Stuart Carter - One of the best experts on this subject based on the ideXlab platform.
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High torsional vibrational energies of H2O2 and CH3OH studied by MULTIMODE with a Large Amplitude Motion coupled to two effective contraction schemes
Molecular Physics, 2009Co-Authors: Stuart Carter, Nicholas C. Handy, Joel M. BowmanAbstract:We have introduced the theory of the Reaction Path Hamiltonian into the variational scheme MULTIMODE, for the calculation of vibrational energy levels of polyatomic molecules which have a single Large Amplitude Motion (for which the classic example is hydrogen peroxide). As with all MULTIMODE calculations, the greatest difficulty is the size of the CI matrix. The algorithm is now enhanced to include user-defined contraction schemes in order to probe high-energy regions of the potential energy surface. Furthermore an increased efficiency in matrix element evaluation is reported. High torsional levels of hydrogen peroxide and methanol are reported; those for hydrogen peroxide are consistent with an ‘exact’ variational procedure in valence coordinates, whilst those for methanol are predictions based on a recently-derived potential energy surface. The coupling between the torsional mode and the remaining normal modes is highlighted. These ‘technical’ advances open up the use of MULTIMODE for the study of vibr...
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The vibrations of glyoxal, studied by 'Multimode', with a Large Amplitude Motion, using an ab initio potential surface
Molecular Physics, 2001Co-Authors: David P. Tew, Nicholas C. Handy, Stuart CarterAbstract:The procedure ‘Multimode’ was introduced by Carter and Bowman [1998, J. chem. Phys., 108, 43971, to calculate the vibrations of polyatomic molecules using normal coordinates. Recently Carter and Handy have introduced an extension to ‘Multimode’ to include one Large Amplitude torsional vibration for molecules for which an analytical potential is available. This procedure is now extended to molecules for which ab initio potential data may be calculated. Glyoxal (CHOCHO) is studied using the density functional approach to generate the potential surface data. The full J = 0 vibrational spectra is presented.
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Glyoxal studied with ‘Multimode’, explicit Large Amplitude Motion and anharmonicity
Physical Chemistry Chemical Physics, 2001Co-Authors: David P. Tew, Nicholas C. Handy, Stuart CarterAbstract:We are studying the vibrations of polyatomic molecules using normal coordinates with our code ‘Multimode ’. Recently we extended ‘Multimode ’ to include one Large Amplitude coordinate, using the theory of the reaction path hamiltonian together with ab initio calculations to obtain the potential energy surface (and its first and second derivatives). Motion perpendicular to the Large Amplitude Motion was therefore assumed to be harmonic. Now we introduce a quartic forcefield. We treat the effects of this anharmonicity in two ways: (i) by the variational method within ‘Multimode’, and (ii) by perturbation theory. This latter approach, which may be called ‘the vibrational adiabatic approximation ’, is particularly attractive because of its simplicity. It opens the way for the study of such vibrations using a combination of Large Amplitude Motion theory, variational theory and perturbation theory. We demonstrate the new approach for glyoxal.
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The vibrations of H2O2, studied by “multimode,” with a Large Amplitude Motion
The Journal of Chemical Physics, 2000Co-Authors: Stuart Carter, Nicholas C. HandyAbstract:Recently Carter and Bowman [J. Chem. Phys. 108, 4397 (1998)] have introduced a variational scheme (“multimode”) for the calculation of rovibrational energy levels of polyatomic molecules using normal coordinates with the Watson Hamiltonian [Mol. Phys. 15, 479 (1968)]. The key to their algorithm is that at most four-mode coupling is allowed in matrix element evaluation. However nearly all Larger molecules have one or more “Large Amplitude” Motions, which are not treatable using normal coordinates. Here we extend multimode to include one Large Amplitude Motion, using the theory of the reaction path Hamiltonian [J. Chem. Phys. 72, 99 (1980)], which is an almost identical problem. Essentially exact variational calculations are possible, and the approach is applied to the vibrations and tunneling Motion of hydrogen peroxide.
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the vibrations of h2o2 studied by multimode with a Large Amplitude Motion
Journal of Chemical Physics, 2000Co-Authors: Stuart Carter, Nicholas C. HandyAbstract:Recently Carter and Bowman [J. Chem. Phys. 108, 4397 (1998)] have introduced a variational scheme (“multimode”) for the calculation of rovibrational energy levels of polyatomic molecules using normal coordinates with the Watson Hamiltonian [Mol. Phys. 15, 479 (1968)]. The key to their algorithm is that at most four-mode coupling is allowed in matrix element evaluation. However nearly all Larger molecules have one or more “Large Amplitude” Motions, which are not treatable using normal coordinates. Here we extend multimode to include one Large Amplitude Motion, using the theory of the reaction path Hamiltonian [J. Chem. Phys. 72, 99 (1980)], which is an almost identical problem. Essentially exact variational calculations are possible, and the approach is applied to the vibrations and tunneling Motion of hydrogen peroxide.
Etienne Guerber - One of the best experts on this subject based on the ideXlab platform.
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A fully nonlinear implicit model for wave interactions with submerged structures in forced or free Motion
Engineering Analysis with Boundary Elements, 2012Co-Authors: Etienne Guerber, Michel Benoit, Stephan T. Grilli, Clément BuvatAbstract:Abstract The purpose of this work is to develop advanced numerical tools for modeling two-way fully nonlinear interactions of ocean surface waves (irregular waves in the general situation) with submerged structures undergoing Large Amplitude Motion, that could represent Wave Energy Converters (WECs). In our modeling approach, an existing two-dimensional Numerical Wave Tank (NWT), based on potential flow theory, is extended to include a submerged horizontal cylinder of arbitrary cross-section. The mathematical problem and related numerical solution are first introduced. Then, conservation of volume and conservation of energy are checked, respectively, in the case of a circular cylinder in a prescribed Large Amplitude Motion and in the case of a circular cylinder in a free Motion. Interactions between waves and a submerged circular cylinder computed by the model are then compared to mathematical solutions for two situations: a cylinder in prescribed Motion and a freely moving cylinder.
