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  • 1
    Electronic Resource
    Electronic Resource
    Hybrid quantum/classical simulation and kinetic study of the vibrational predissociation of Cl2(centered ellipsis)Nen (n=2, 3) (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4577-4588 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A hybrid quantum/classical method is applied to the vibrational predissociation of van der Waals clusters containing a diatomic molecule and several rare gas atoms, Cl2(centered ellipsis)Nen (n=2, 3). The vibrational degree of freedom of the diatomic is treated quantum mechanically while all the other degrees of freedom are treated classically. A kinetic mechanism is proposed in order to interpret the dynamics in terms of the following elementary steps; vibrational predissociation (VP), intramolecular vibrational redistribution (IVR), and evaporative cooling (EC). The resulting lifetimes are in very good agreement with the experimental linewidth measurements of Janda and co-workers, and with the quantum mechanical reduced-dimension results of Le Quéré and Gray on Cl2(centered ellipsis)Ne2. The final rotational state distributions agree very well with the experimental results and exhibit a quasistatistical behavior. The final vibrational distributions reproduce the main experimental features. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479219
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of highly excited rovibrational states for N2O using generalized internal coordinates (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 6339-6352 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Generalized internal vibrational coordinates are optimized and used to describe highly excited vibrational motions in the N2O molecule. These coordinates are defined as the magnitudes of two vectors, which are expressed as linear combinations of the internal displacement vectors and the angle formed between them. They depend on two parameters and contain, as particular cases, valence and orthogonal (Jacobi, Radau, etc.) coordinate systems. The coordinates are optimized by minimizing unconverged variationally computed vibrational energies with respect to the external parameters. A comparison of the optimal internal coordinates derived for N2O with valence and hyperspherical normal coordinates is made. The optimal internal coordinates are also used to determine a new potential energy function for N2O from the observed vibrational frequencies up to 15 000 cm−1 using fully variational calculations. The quality of the adjusted potential energy function is checked by computing vibrational-rotation energy levels and rotational constants for Σ, Π, Δ, Φ, and Γ states and comparing them with the observed values. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478538
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  • 3
    Electronic Resource
    Electronic Resource
    Variational calculations of vibrational states of N2O using hyperspherical normal coordinates (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6099-6110 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Accurate variational calculations are presented for highly excited vibrational bound states of N2O using different recently proposed ab initio and empirical potential energy surfaces. All these potential surfaces are expressed as series expansions in terms of internal displacement coordinates. Transformations of them into Simons, Parr and Finlan (SPF) and Morse expansion are also considered. The vibrational state calculations are performed using a set of curvilinear hyperspherical normal coordinates derived from Radau coordinates. The vibrational energies are compared with experimental data and the quality of the potential energy surfaces used is discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472469
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of the I2(X)(centered ellipsis)Ar isomers population in a free-jet expansion: Thermodynamics versus kinetic control (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 1944-1953 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A molecular dynamics simulation addressing the problem of thermodynamic versus kinetic control of the isomers population of van der Waals complexes in a supersonic expansion is presented. The populations of the linear and T-shaped isomers of I2(X)(centered ellipsis)Ar in a supersonic beam expansion were determined by molecular dynamics simulation as a function of the distance to the nozzle and compared to the prediction of thermodynamics. The surprising conclusion is that although there is a barrier equal to half the well depth between the two isomers, their populations are consistent with the existence of thermodynamic equilibrium. This result is rationalized by examining the cooling mechanisms in the Ar+I2(X)(centered ellipsis)Ar collisions. In addition to the direct isomerization, a new mechanism (swap cooling), which induces isomerization even for complexes with barriers above the dissociation limit, is evidenced. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1431275
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  • 5
    Electronic Resource
    Electronic Resource
    Optimal generalized internal vibrational coordinates and potential energy surface for the ground electronic state of SO2 (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 139-148 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An optimization of generalized internal vibrational coordinates for the electronic ground state of the SO2 molecule is carried out. These coordinates are given by the magnitudes and the angle formed by two vectors expressed as linear combinations of the internal valence vectors, and depend on two external parameters which can be optimized so as to reduce the vibrational coupling of the molecule as much as possible. The optimal values of the parameters are found by minimizing a set of unconverged vibrational energies which are computed variationally using a small basis function set. It is shown that the optimal internal coordinates obtained for SO2 are superior to both valence and Radau coordinates, as well as to a set of normal coordinates previously derived by proper rotation of the Jacobi S–O2 coordinates. These optimal internal coordinates are then applied to calculate the vibrational energies of the molecule using an ab initio force field expressed as a Morse-cosine expansion, and then to refine it by nonlinear least-squares fitting to the observed vibrational frequencies. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1377893
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  • 6
    Electronic Resource
    Electronic Resource
    Erratum: "Time evolution of reactants, intermediates and products in the vibrational predissociation of Br2⋅⋅⋅Ne: A theoretical study" [J. Chem. Phys. 113, 10130 (2000)] (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 7713-7713 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The lower part of Fig. 6 was erroneous, due to a transcription error. The MDQT and experimental results now show a much better agreement with the quantum mechanical ones for the Δv=−2 channel of the Br2⋅⋅⋅Ne(v=27) vibrational predissociation, as was the case for the other channels and the other initial vibrational levels. The rest of the paper is unchanged. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1361066
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  • 7
    Electronic Resource
    Electronic Resource
    A theoretical study of the vibrational spectrum of the CS2 molecule (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 7495-7508 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical study of the vibrational spectrum of the CS2 molecule is carried out. For that purpose, a new Morse-cosine potential energy function is determined by fitting to observed vibrational frequencies, using as a starting point an ab initio force field. Highly excited vibrational states for CS2 are then calculated up to 20 000 cm−1 using a DVR truncation-diagonalization method. Hyperspherical Radau coordinates, which are a set of normal curvilinear coordinates for linear symmetric triatomic molecules, are used in these calculations. The computed vibrational energy levels are shown to present an excellent agreement with the observed values up to 13 000 cm−1. Based on these calculations, some unassigned observed vibrational frequencies are identified and the assignments of others are reconsidered. Inspection is made of the vibrational wave functions computed for CS2 revealing a persistent regularity up to 13 000 cm−1. This regularity is found to be consistent with perturbation theory results for these energies. Van Vleck perturbation theory is used to derive effective Hamiltonians that contain polyad quantum numbers and that provide good agreement with the variational calculations. It is also shown that the asymmetric stretch is practically decoupled from the symmetric stretch and the bend in this range of energies. The nearest neighbor space distribution (NNSD) and the Δ3 spectral rigidity function show that the calculated vibrational spectrum of CS2 up to 20 000 cm−1 is essentially regular, in agreement with the most recent statistical analyses made of the spectroscopically observed frequencies.© 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1465413
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  • 8
    Electronic Resource
    Electronic Resource
    A theoretical study of the HgAr2(3P1←1S0) vibronic spectrum (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 1007-1017 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quantum mechanical calculation of the vibronic spectrum of the HgAr2 van der Waals cluster in the region of the Hg(3P1←1S0) electronic transition is presented and compared with experiments. The potential energy surfaces for the ground and excited states are obtained using available empirical Ar–Ar and Ar–Hg potentials. For the ground electronic state, the potential is written as a sum of pairwise Ar–Ar and Ar–Hg(1S0) interactions. On the contrary, for the electronically excited states correlating to Hg(3P1), an axis switching rotation has to be applied to each individual Ar–Hg(3P1; Ωe=0, ±1) interactions in order to define a common quantization axis. This results in a nonpairwise additive diabatic matrix Hamiltonian which after diagonalization provides the adiabatic excited potential energy surfaces. The vibrational wave functions associated to the ground and the first two (A˜ and B˜+) adiabatic electronically excited states are obtained by variational techniques using basis sets along Jacobi coordinates. Analysis of the wave functions reveals that the normal mode description is valid only for the very few first levels and that strong mode mixing prevails through all the rest of the spectrum. For the B˜+ state, the calculated and observed spectra compare well, while for the A˜ state, some discrepancies are found. Possible reasons for these differences are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464326
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  • 9
    Electronic Resource
    Electronic Resource
    Investigations of transformed mass-scaled Jacobi coordinates for vibrations of polyatomic molecules with application to H2O (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2708-2713 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an investigation of orthogonal transformations of Delves coordinates, i.e., mass-scaled Jacobi coordinates, in applications to polyatomic molecule vibrations. First, we show for triatomic molecules with a stationary point of C2v symmetry that these coordinates can be transformed exactly to yield normal coordinates in the small displacement limit. A partial transformation to normal coordinates is also given for tetraatomic molecules with C2v symmetry. Second, we show that this transformation can be used to optimize a set of coordinates for use in variational calculations of vibrations of polyatomic molecules, and demonstrate its utility in variational calculations of vibrational energies for H2O.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455918
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  • 10
    Electronic Resource
    Electronic Resource
    Self-consistent-field calculation of vibrational bound states for triatomic molecules using transformed Jacobi coordinates (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 2292-2297 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100159a035
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