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  • 1
    Electronic Resource
    Electronic Resource
    Multistate vibronic interactions in the benzene radical cation. I. Electronic structure calculations (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 2645-2656 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multistate vibronic interactions in the benzene radical cation are investigated theoretically, employing the framework of a linear vibronic coupling scheme. The five lowest electronic states are included in the treatment; in view of the degeneracy of some states, this amounts to eight coupled potential energy surfaces. Different types of ab initio calculations have been performed for the system parameters and been found to be in good mutual agreement, thus supporting each other. The calculations reveal a whole sequence of low-energy conical intersections between the potential energy surfaces of different states. Their importance for the nuclear dynamics in this prototypical organic radical cation is pointed out. Wave-packet dynamical simulations for these coupled potential energy surfaces will be presented in the following paper (Paper II). © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491397
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  • 2
    Electronic Resource
    Electronic Resource
    Barrier recrossing in the vinylidene–acetylene isomerization reaction: A five-dimensional ab initio quantum dynamical investigation (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 7907-7923 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The spectroscopy and dynamics of the vinylidene–acetylene isomerization reaction are studied theoretically. Based on a new ab initio potential energy surface, the nuclear dynamics is followed by grid methods and wave packet propagation techniques. All five planar degrees of freedom are included in the calculation, for all three different isotopomers. The experimental photoelectron spectra by Lineberger and co-workers are very well reproduced; upon a small adjustment of the calculated anionic equilibrium geometry the agreement becomes excellent. The vinylidene survival probability for broadband photodetachment exhibits three different time regimes, the longest of which points towards an unusual stability of this reactive intermediate. The latter finding is corroborated by the calculated state-specific lifetimes which exceed previous estimates in the literature by ∼3 orders of magnitude. These findings are found to be reconfirmed when taking the discrete level structure of vibrationally highly excited acetylene into account. They amount to heavy barrier recrossing effects in this isomerization reaction and lend strong support to the interpretation of CEI experiments on vinylidene by Levin et al. where this species has been identified ∼3 μs after its formation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1405120
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  • 3
    Electronic Resource
    Electronic Resource
    Spectral quantization of transition state dynamics for the three-dimensional H+H2 reaction (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1725-1729 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Applying a spectral quantization method, we find the positions and widths of 32 transition state resonances in the three-dimensional reaction H+H2 with J=0. The assignment of many of the resonances appears to follow asymmetric stretch and bend progressions for a linear triatomic molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467728
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  • 4
    Electronic Resource
    Electronic Resource
    Spectra and time-dependent dynamics of H3 near the conical intersection in the (2p)1E′ ground electronic manifold (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 1721-1733 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report on the spectra and dynamics of H3 near the conical intersection in its (2p)1E′ ground electronic manifold. The time-dependent wave packet approach and the double many-body expansion (DMBE) potential energy surface (PES) are employed for this purpose. We use Jacobi coordinates (R,r,γ) and employ the fast Fourier transform method for R and r, and the discrete variable representation method for γ, in conjunction with the split-operator formalism to describe the evolution of the wave packet (WP) in space and time, respectively. While the main focus of the present work is to explicitly reveal the effects of nonadiabatic coupling between the two sheets of the DMBE PES, companion calculations are also carried out to investigate the dynamics on the uncoupled upper and lower adiabatic sheets, both in two and three dimensions (for total angular momentum J=0). A set of pseudospectra is calculated by Fourier transforming the time autocorrelation function of suitably chosen Gaussian wave packets located initially at the minimum energy point of the seam of conical intersections. The eigenstates thus obtained are assigned by computing their eigenfunctions by spectral quantization. In the coupled states treatment the WP is propagated in the diabatic representation. The time dependence of the adiabatic populations is calculated by using suitable adiabatic projection operators. We find strong effects of nonadiabatic coupling on the discrete vibrational energy levels of the upper adiabatic sheet, which all change to quasibound states in the coupled manifold. The comparison of the decay dynamics of various levels of the upper adiabatic sheet indicates considerable mode specificity (their lifetimes typically vary between 3 and 6 fs). On the other hand, resonances are seen to be less pronounced near the conical intersection on the lower adiabatic sheet (when compared to those in the literature, obtained near the collinear saddle point region). The effect of nonadiabatic coupling on them is only minor. We also report preliminary results on the optical emission spectrum of H3 and compare them with the experimental findings. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476746
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  • 5
    Electronic Resource
    Electronic Resource
    Geometric phase effects and wave packet dynamics on intersecting potential energy surfaces (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 9292-9303 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The impact of the geometric phase on the time evolution of quantum-mechanical wave packets is studied theoretically. Two model systems of coupled electronic potential energy surfaces are compared. One of them, the well-known E×e Jahn–Teller system, comprises two conically intersecting surfaces, and the dynamics is subject to the geometric phase. The other system, describing the (E+A)×e Pseudo-Jahn–Teller effect, comprises three intersecting surfaces and the dynamics is not subject to a geometric phase. Apart from the geometric phase, the coupling to the upper surface is verified to be negligible for low-energy wave packet motion. Still, the geometric phase leads to a pronounced difference of low-energy wave packet dynamics in both systems. Most significant is the phenomenon of destructive self-interference of the two parts of the wave packet that encircle the conical intersection on opposite sides. The importance of the resulting different shape of the wave packet for a fs pump-probe spectrum is pointed out. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469988
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  • 6
    Electronic Resource
    Electronic Resource
    Geometric phases and quantum dynamics in spin–orbit coupled systems (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1503-1513 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The quantum dynamics of vibronically interacting systems with additional effects of spin–orbit coupling is studied theoretically. The combined effects of spin–orbit and vibronic coupling lead to geometric phases which can vary smoothly between the case of uncoupled potential energy surfaces (vanishing geometric phase) and the limiting case pertinent for conically intersecting surfaces (geometric phase equals π). The impact of these phases on the nuclear energy levels and wave functions is revealed by companion studies for two and three coupled potential energy surfaces including and suppressing the geometric phase effects. For free pseudorotation the resulting effective angular momentum can take any noninteger value. The stationary wave functions exhibit a corresponding smooth transition between the limiting cases of integer and half-odd integer angular momentum. For localized wave packets with high angular momentum the geometric phase increases in the same way as found when treating the nuclear coordinates as classical variables. For delocalized wave packets destructive interference leads to a complete loss of symmetry and, for longer times, to a different overall shape of the wave packet. The effects can be relevant also when the nonadiabatic coupling to the higher potential energy surface is negligible. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475522
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  • 7
    Electronic Resource
    Electronic Resource
    Photoelectron spectroscopy of C4H4−: Ab initio calculations and dynamics of the 1,2-hydrogen shift in vinylvinylidene (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 1250-1262 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ultraviolet photoelectron spectrum of HXC=C− (X=C2H3) is reported along with ab initio calculations. The adiabatic electron affinity of the X 1A′ state is measured to be 0.914(15) eV for C4H4 and 0.909(15) eV for C4D4. The term energy of the C4H4 a˜3A′ state is 1.923(15) eV and the b 3A″ term energy is 2.035(30) eV. Geometries and frequencies of several stationary points on the C4H4 and C4D4 neutral and anion surfaces at the configuration interaction with singles and doubles level of theory are reported, as well as an intrinsic reaction coordinate calculation at the restricted Hartree Fock level on the C4H4 singlet surface. Calculations and experiment are combined to estimate the lifetime of singlet vinylvinylidene for rearrangement to vinylacetylene to be 20–200 fs, corresponding to lifetime broadening of 35–3 meV. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469801
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  • 8
    Electronic Resource
    Electronic Resource
    Diisocyan oder Cyanisocyan?Wir danken C. A. deLange, Amsterdam, für die Vorabmitteilung des Pe-Spektrums und für viele interessante Diskussionen. (1989)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 101 (1989), S. 770-771 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19891010617
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  • 9
    Electronic Resource
    Electronic Resource
    Symmetriebrechung und Nicht-Born-Oppenheimer-Effekte in Radikalkationen (1983)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 95 (1983), S. 221-236 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die verschiedenen elektronischen Zustände, in denen Moleküle existieren können, werden oft als voneinander unabhängig betrachtet. Thematik des vorliegenden Aufsatzes ist es, die Grenzen dieser Annahme zu verdeutlichen, nämlich die Wechselwirkung zwischen verschiedenen elektronischen Molekülzuständen durch die Kernbewegung. Diese Wechselwirkung kann mehrere wichtige Konsequenzen haben, von denen zwei im Detail diskutiert werden. Die erste ist eine Verzerrung des Kerngerüstes des Moleküls, was zu einer Symmetrieerniedrigung in angeregten oder ionischen Zuständen gegenüber dem Grundzustand der neutralen Spezies führt. Allgemeine Merkmale dieser Symmetrieerniedrigung werden anhand typischer Beispiele interpretiert. Die andere Konsequenz der Wechselwirkung ist die Möglichkeit, daß die Atomkerne während ihrer Schwingungsbewegung zwischen verschiedenen Potentialflächen des Moleküls hin- und herspringen (Nicht-Born-Oppenheimer-Effekte). Das Wesen dieses Verhaltens wird untersucht, und es wird gezeigt, daß das “Springen” sehr schnell vor sich gehen und die Kernbewegung vollständig beherrschen kann. Zur Veranschaulichung unserer allgemeinen Ideen benutzen wir die Photoelektronen-Spektren von Ethylen und verwandten Verbindungen und weisen in ihnen das Auftreten starker Nicht-Born-Oppenheimer-Effekte nach. Es stellt sich heraus, daß hier das Franck-Condon-Prinzip bei der Analyse der Schwingungsstruktur versagt.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19830950306
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  • 10
    Electronic Resource
    Electronic Resource
    Vibronic Coupling. Von G. Fischer. Academic Press, London 1984. VIII, 222 S., geb. $ 42.00. - ISBN 0-12-257240-8 (1986)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 98 (1986), S. 578-578 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19860980634
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