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  • 1
    Electronic Resource
    Electronic Resource
    Ab initio investigation of the vibrational structure of absorption and emission spectra of FCO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3981-3988 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of an ab initio study of the vibrational structure of several electronic spectral systems of FCO are presented. An interpretation of hitherto recorded spectra, as well as a prediction of features of yet unobserved electronic transitions is given. The absorption spectra observed in the uv spectral region are ascribed to the transitions involving the first excited states of 2A' and 2A‘ character. The emission spectrum obtained by Toby and Toby [J. Phys. Chem. 85, 4071 (1981)] is assigned to the transition X 2A'←2 2A‘. Reassignment of some observed vibrational bands is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467516
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  • 2
    Electronic Resource
    Electronic Resource
    Ab initio study of the potential energy surfaces of doublet valence and Rydberg states of FCO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3973-3980 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Multireference configuration interaction calculations (MRD-CI) were carried out in order to obtain the bending and stretching potential energy curves of several low-lying electronic states of the fluoroformyl radical FCO. The study of interactions between valence and Rydberg states as well as that of the dissociative behavior is included in the investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467515
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  • 3
    Electronic Resource
    Electronic Resource
    Bound states and time-dependent dynamics of the N2H+ molecular ion in its ground electronic state. I. 2D treatment (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 2930-2941 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ground-state potential energy surface (PES) for linear arrangements of the N2H+ molecular ion is numerically computed by the multireference single- and double-excitation configuration interaction (MRD-CI) technique. An analytical representation of the potential energy function is obtained by fitting a power series in the Simons–Parr–Finlan coordinates to the numerical data. For investigating the intramolecular dynamics we describe the nuclear motion by a Gaussian wave packet located initially in the strong interaction region of the PES. The vibrational eigenvalue spectrum is calculated by Fourier transforming the time autocorrelation function. The spectrum is then analyzed statistically in the light of random matrix theory (RMT) to understand the nature of the intramolecular dynamics. We examine the short-range correlation in the spectrum through the nearest neighbor level spacing distribution P(s) and the long-range correlation through Δ3 and Σ2 statistics. The spectrum in the time domain is analyzed by computing the ensemble averaged survival probability 〈〈P(t)〉〉. The above four quantities obtained from the spectrum are compared with the distribution predicted for regular, irregular, and mixed (intermediate) spectra by the RMT. We find the system is of mixed type and the fractional irregularity is 0.7±0.05. In order to reveal a possible correspondence to the classical dynamics, we have carried out the spectral analysis of the dynamical variables for classical trajectories over a wide range of internal energies. In addition the classical dynamics of proton collisions with N2 molecules has also been preliminarily studied on the same PES, in particular the dependence of the final vibrational action nf on the initial vibrational phase φi of N2 and, furthermore, the Poincaré surface-of-section superimposed with the zero-order separatrix; we find a large number of trapped trajectories. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474651
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  • 4
    Electronic Resource
    Electronic Resource
    Photodissociation of NH2: Two-dimensional potential energy surfaces for the dissociation into NH and H (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5558-5571 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Extensive multireference configuration interaction calculations were carried out in order to obtain complete two-dimensional (2D) potential energy surfaces for the amidogen (NH2) radical as functions of both N–H bond lengths keeping the bond angle fixed at its experimental ground state equilibrium value. The eight lowest-lying states (four of each symmetry, A′ and A″) were treated mainly for the purpose of using these surfaces in subsequent studies of the photodissociation dynamics. In analogy with the neighboring dihydrides CH2 and H2O the photodissociation of NH2 into NH+H (hydrogen abstraction) takes place preferentially after excitation of the first two Rydberg s states (3 2A′/2 2A1 and 2 2A″/2 2B1) found closely together at about 7.6 eV. The transition dipole moments connecting the ground state with these two states are large (0.44 a.u. and 0.66 a.u.) in the Franck–Condon region, but the behavior of the potentials in the dissociation channel is quite different. The 3 2A′/2 2A1 state is weakly repulsive whereas the 2 2A″/2 2B1 state is strongly repulsive. This will result in differences in the dissociation dynamics for the two states.The next higher state which should play a role in the NH2 photodissociation is the 4 2A″/3 2B1 Rydberg s state at 9.4 eV, because of its large transition dipole moment with the ground state (0.36 a.u.). Close to this state, many Rydberg p states were found. Due to the high density of states in the region above 9.0 eV, interactions of these states are expected and should lead to complicated dissociation dynamics. Contrary to CH2, the two low-lying valence states for NH2 are found at lower energies [2.2 eV (1 2A1) and 6.5 eV (1 2B2)], well separated from the first members of the Rydberg series. These states are less important for the photodissociation of NH2, compared with CH2, because the first state is bound and the transition to the other is dipole-forbidden in C2v symmetry. For H2O, the valence states are missing. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471796
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  • 5
    Electronic Resource
    Electronic Resource
    Zum C-H-Bindungsmoment von Methan, Äthan, Äthylen und Acetylen (1968)
    Springer
    Theoretical chemistry accounts 12 (1968), S. 313-318 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels lokalisierter Ladungsverteilungen für die C-H-Bindung von Methan, Äthan, Äthylen und Acetylen, bestimmt aus Minimalbasis-SCF-LCAO-MO-Näherungen, wurden C-H-Bindungsmomente berechnet. Die Ergebnisse liegen im Bereich zwischen ungefähr 1,75 und 2,0 D (C(+)-H(−)). Die Abhängigkeit der berechneten Werte von C-H-Kernabstand, Orbitalparametern, Lokalisierungsverfahren und benachbarten Bindungen wird diskutiert.
    Abstract: Résumé Calcul des moments de liaison C-H à l'aide de charges localisées déterminées à partir de fonctions d'onde SCF-LCAO-MO, en base minimale, pour le méthane, l'éthane, l'éthylène et l'acétylène. Les résultats se trouvent situés entre 1,75 et 2,0 D (C(+)-H(−)). On discute la relation existant entre les valeurs calculées et la longueur de la liaison C-H, les paramètres orbitaux, le procédé de localisation et l'environnement.
    Notes: Abstract By means of localized charge distributions for the C-H bond of methane, ethane, ethylene, and acetylene, determined from minimalbasis SCF-LCAO-MO wavefunctions, C-H bond moments have been calculated. The results lie in the range between about 1.75 and 2.0 D (C(+)-H(−)). The dependence of the computed values upon C-H distance, orbital parameters, localization procedure, and neighbouring bonds is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527547
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  • 6
    Electronic Resource
    Electronic Resource
    Zur Bereehnung des Behinderungspotentials der inneren Rotation von Wasserstoffperoxid (1966)
    Springer
    Theoretical chemistry accounts 5 (1966), S. 139-147 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Resume On calcule à l'aide du théorème de Hellmann Feynman le potentiel de rotation interne de H2O2. La distribution de charge électronique de la liaison OH nécessaire pour ce calcul est représentée par une fonction de liaison à 2 centres tirée d'un calcul d'orbitales de liaison de l'eau. Le développement en série de Fourier du potentiel donne:U(τ) = 3.780 + 5.248 cos τ + 2.592 cos 2 τ + 0.142 cos 3 τ [kcal · Mol−1] . Pour les barrières de potentiel on obtient les valeursU cis = 11.76 et Urane = 0.98 kcal/Mole; l'angle d'équilibre est trouvé égal à 120° 5.
    Abstract: Abstract Using the Hellmann-Feynman-theorem the potential of internal rotation of H202 is calculated, the electronic charge distribution being represented by two-center bond orbitals andsp 3 hybrid orbitals (for the lone pairs). Developing the calculated potential in a Fourier series leads to the above-mentioned formula. The potential barries are 11.76 and 0.98 kcal/Mole, the angle of twist of equilibrium is 120.5°.
    Notes: Zesummenfassung Auf der Grundlage des Hellmann-Feynman-Theorems wird das Behinderungspotential der inneren Rotation von H202 berechnet unter Verwendung einer genäherten Elektronendichteverteilung, in welcher zweizentrige Bond-Orbitale die Bindungselektronen undsp 3-Hybride die einsamen Elektronenpaare beschreiben. Eine dreitermige Fourier-Approximation des erhaltenen Potentialverlaufs hat die Gestalt:U(τ) = const. + 5,248 · cos τ + 2,592 · cos 2 τ + 0,142 · cos 3 τ [kcal · Mol−1] . Für die PotentialschwellenU cis undU trans ergeben sich 11,76 bzw. 0,98 kcal · Mol−1, dem Minimum der Potentialkurve entspricht ein Torsionswinkel von 120,5°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01138856
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  • 7
    Electronic Resource
    Electronic Resource
    Ionized van der Waals systems: Structure and interactions (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 64 (1997), S. 211-222 
    Details
    ISSN: 0020-7608
    Keywords: quantum chemistry ; weak interactions ; cationic van der Waals complexes ; cluster cations ; potential energy surfaces ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ions of molecular complexes with internal interactions partly of van der Waals type differ significantly from their neutral parent species in binding, structure, and dynamics. Information about such systems is still rather scarce, both experimentally and theoretically. The article discusses some aspects of the present knowledge concerning cationic dimers and trimers of the type RgnM+ with Rg denoting a rare-gas atom, and M, either a (diatomic) molecule or a rare-gas atom, in comparison with the neutral counterparts. In some more detail, potential energy surfaces (PESs) for the six lowest electronic states of ArHCl+ are reported, as obtained from multireference CI calculations with an extended Gaussian AO basis set. From the PESs, structural, energetical, and dynamical features are derived. For the cationic argon trimer Ar3+ in the electronic ground state, a detailed analysis of the PES, the mode couplings, and the classical internal dynamics is carried out, leading to a consistent picture of a floppy molecular aggregate with rapid energy exchange between internal degrees of freedom and early onset of classical chaos with increasing energy.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64: 211-222, 1997
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Internal dynamics of simple floppy molecules (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 227-245 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dynamical behavior of simple nonrigid molecules still attracts much interest both from experimentalists and theoreticians. On the one hand, modern laser-spectroscopic techniques like SEP allow for the detection of highly excited vibrational-rotational states of a molecule, and advanced theoretical methods, on the other hand, are more and more able to calculate accurate potential energy surfaces and to simulate the intramolecular dynamics. The aim of the present article was to contribute to the understanding of the dynamical properties of simple floppy molecules by means of a comparative study of the two triatomics HCN and HO2. Continuing our earlier work, we start from an analysis of the potential energy surface topography, then we investigate the classical dynamical behavior and the localization of the quantum states. Several conclusions of probably more general validity are drawn. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520122
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  • 9
    Electronic Resource
    Electronic Resource
    Theoretical approach to reactions of polyatomic molecules (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 191-208 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A scheme for systematic reduction of the theoretical treatment of elementary reactions involving polyatomic molecules is described; it consists of (1) limitation to the energetically relevant regions of the nuclear configuration space (the reaction path and its near environs) and (2) restriction to the dynamically relevant subspace of the nuclear configuration space (the active modes). Starting from a generalized reaction path Hamiltonian of Nauts and Chapuisat allowing for the use of arbitrary curvilinear coordinates and several large-amplitude modes, the realization of the above-sketched scheme is discussed. A compilation of recent work along these lines, mostly based on the simplified Miller-Handy-Adams reaction path Hamiltonian, is given with particular emphasis on applications of a statistical adiabatic model.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380214
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