Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Accounts of chemical research 22 (1989), S. 223-229 
    ISSN: 1520-4898
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 100 (1978), S. 2984-2991 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1116-1124 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A variational transition state theory is formulated for the decay rate of a particle trapped in a metastable potential well and coupled to a heat bath. Rigorous upper bounds are derived for the transmission coefficient and the rate constant. The variational theory leads to minimization of the flux of an effective two degree of freedom Hamiltonian whose parameters depend on the system potential and the time dependent friction kernel. An explicit solution for the canonical variational dividing surface in the presence of nonlinearities in the system potential is provided. The Kramers expression for the rate in the spatial diffusion limit and its generalization to memory friction, is shown to give upper bounds provided that the nonlinearity in the system potential is positive definite. However, the variational result can still lead to substantially lower bounds for the rate. An application of VTST to a symmetric cusped double well potential provides a new expression for the rate, valid for arbitrary friction kernels and damping strength.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 3005-3017 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Two degrees of freedom quantum mechanical calculations on the bound states of H+3 are presented. Two different potential energy surfaces are employed. The effect of rotational excitation is analyzed. For J=0, the high energy region is composed largely of states that cannot be assigned. However, two regularly spaced series are observed, corresponding to "horseshoe'' states predicted previously by classical calculations. In addition we find a new assignable series of inverted hyperspherical states. Conversely, for high orbiting angular momentum (l=20) in which the proton rotates about the diatom, assignable normal mode states persist up to dissociation. Semiclassical periodic orbit quantization is found to give excellent agreement for the regular quantum states. The significance of these results for the interpretation of the H+3 photodissociation spectrum is discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5406-5419 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation spectrum of H+3 is studied using classical mechanical methods. Tunneling rates and product translational energies are computed for a large range of total angular momentum and energy. We predict that the experimentally measured spectrum of Carrington and Kennedy is dominated by low total angular momentum and low energy (relative to dissociation). There is an almost one to one correspondence between the measured product translational energy and the total angular momentum. The classical dipole spectrum of chaotic trajectories is found to be relatively structureless, changes slowly with total J, and does not show any correspondence or indication of the experimentally measured regular structure found in the coarse grained spectrum. We conclude that the regularity found in the coarse grained spectrum should be associated with a stable manifold of trajectories. We find that the horseshoe periodic orbit previously found to be stable at J=0 exists also for nonzero J and is stable with respect to small perturbations in 3D. The rotational constant of the rotating horseshoe is 30 cm−1 in interesting agreement with the experiment. The properties of the rotating horseshoe are studied in detail, a novel adiabatic switching method is used to study the stability of the orbit. A quantum formalism of Taylor and Zakrzewski that shows how periodic orbits may cause structure in quantal spectra is used to indicate why the features of the rotating horseshoe orbit may appear in the coarse grained spectrum. The experimental coarse grained features are interpreted as an R branch of the ν3 mode of the rotating horseshoe.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5643-5656 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recently, Kennedy and Carrington found new quasibound states of H+3, which lie up to 1 eV above the dissociation limit with lifetimes as long as 1 μs. In an effort to understand the structure of these states, we investigate classically bound states embedded in the dissociative continuum of this molecule. In the first part, we assume J=0, and specialize to one of the two symmetries, C∞V or C2V. Poincaré surfaces of section are used to demonstrate the existence of a small region of bound phase space in these 2D problems, but stability analysis of the periodic orbits show that most of them are unstable in 3D. We conclude that J=0 or, more generally, low J states cannot explain the experiments. In the second part we treat the case J〉0. A total angular momentum centrifugal barrier provides a classically rigorous boundary, which separates the phase space into two parts: a dissociative and a bound region. Wells and double wells exist. Trajectories in these wells show quasiperiodic or chaotic character, depending on the total angular momentum, and on the energy relative to the bottom of the well. Quantally, these states can dissociate by tunneling. One finds long lifetimes in qualitative agreement with the experiments. The volume of the bound part of the phase space is determined by Monte Carlo integration. Typically, several thousand resonance states are found for any J between 20 and 50. This suffices (in principle) to explain the very large number of experimentally observed lines.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1596-1603 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It was recently suggested that vibrational excitation of van der Waals molecules could lead to prereaction instead of predissociation. A mechanism for vibrational prereaction based on tunneling of a light atom is proposed and tested. The effect of van der Waals wells on the reactivity of collinear MuD2, ClHBr, and ClHCl systems is studied. We find that vibrational prereaction is sensitive to the ratio of tunneling and vibrationally nonadiabatic interaction. If tunneling dominates, prereaction will take place. This is the case for the ClHBr and ClHCl systems. The interplay between reaction probability and photodissociation cross sections is studied. We conclude that vibrational prereaction will lead to an increase in reaction probability and an increase in the formation of products in photodissociation. This study suggests that vibrational prereaction could be observed at least in principle in light atom transfer systems.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1079-1088 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper shows how to quantize Hamiltonians of symmetric ABA molecules using energies and stability frequencies of simple normal and local mode periodic orbits. It is shown that the quantization can be based either on the idea of adiabatic dynamical potentials or on the hindered rotor representation. In the former case, the stable periodic orbits correspond to the wells and the unstable ones to the barriers of the adiabatic potentials. In the latter case the normal mode periodic orbits correspond to the equilibria of the hindered rotor Hamiltonian, and the local mode periodic orbits correspond to the rotor's orbits with the maximal allowed "angular momentum.'' Results of extensive numerical testing of both approaches are presented for the H2O model Hamiltonian used by Sibert et al., and for the Davis–Heller potential.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 3944-3949 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recently measured isomerization rates of trans-stilbene and diphenylbutadiene over a very large pressure range indicate that a medium can seemingly increase the rate beyond the gas phase high pressure limit. A model based on a generalized Langevin equation is proposed and solved using transition state theory. Rates obtained are in good agreement with experiment. The model incorporates a solvent shift which lowers the barrier to reaction. The model is based on the unification of two different approaches to the description of a dissipative harmonic bath.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4073-4087 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An analytical theory is formulated for the thermal (classical mechanical) rate of escape from a metastable state coupled to a dissipative thermal environment. The working expressions are given solely in terms of the quantities entering the generalized Langevin equation for the particle dynamics. The theory covers the whole range of damping strength and is applicable to an arbitrary memory friction. This solves what is commonly known as the Kramers turnover problem. The basic idea underlying the approach is the observation that the escape dynamics is governed by the unstable normal mode coordinate—and not the particle system coordinate. An application to the case of a particle moving in a piecewise harmonic potential with an exponentially decaying memory-friction is presented. The comparison with the numerical simulation data of Straub, Borkovec, and Berne [J. Chem. Phys. 84, 1788 (1986)] exhibits good agreement between theory and simulation.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...