ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
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
    Spherical wave close coupling wave packet formalism for gas phase nonreactive atom–diatom collisions (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 339-349 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we discuss the use of the total angular momentum representation in the close coupling-wave packet (CCWP-J) method for solving the time dependent Schrödinger equation for inelastic, nonreactive gas phase atom–diatom collisions. This enables the wave packet propagation for the relative motion to be reduced from three dimensions to one. The approach utilizes a close coupling expansion of the wave packet into subpackets labeled by quantum numbers for total angular momentum J, z-component of angular momentum m0, rotor angular momentum j, and orbital angular momentum l. The number of coupled subpackets is less than the number for the plane wave boundary condition CCWP method when J〈jmax and they are equal when J≥jmax. The present method requires solving for the time evolution of such coupled subpackets for 0≤J≤jmax +lmax, where lmax is the largest orbital angular momentum for which significant scattering occurs. However, the number of grid points required in the fast Fourier transform portion of the evolution of the wave packet will be far fewer since only a 1D FFT transform is required in the present version of the CCWP-J. All the other attractive features of the CCWP method are common to both the total angular momentum and plane wave representation versions of the CCWP; namely, results are obtained over the range of energies included in the initial packet, the labor scales as the number of rotor states squared, and standard approximation methods may be used in conjunction with the formalism. We also present the l-labeled coupled states or centrifugal sudden wave packet (CSWP) formalism as an example approximate version of this approach. The CCWP-J method is illustrated by application to a model atom–diatom collision problem. The extension to treat collisions involving a vibrating rotor is given in an Appendix. Finally, we compare features of the CCWP-J and CSWP with standard close coupling, CS approximation, and the plane wave basis CCWP methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453633
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Close coupling-wave packet formalism for gas phase nonreactive atom–diatom collisions (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2087-2094 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we discuss the adaptation of the close coupling-wave packet (CCWP) method for solving the time dependent Schrödinger equation for inelastic, nonreactive gas phase atom–diatom collisions. The approach is novel in that (a) it is an initial value rather than boundary value method, (b) it can be formulated to either avoid or include the partial wave expansion normally used for gas phase atom–diatom collisions, (c) it can be formulated to determine either a single column of the differential scattering amplitude matrix or S matrix rather than the full matrix, (d) the labor involved in a single calculation scales with the number of rotor states squared rather than cubed as in standard close coupling, (e) a single calculation yields numerically exact results over the full range of energies contained in the original wave packet, and (f) results for other initial states can be obtained by means of the energy sudden (ES) or energy corrected sudden (ECS) factorization relations. The analysis for extracting the differential scattering amplitude at fixed energies is given in detail because it differs markedly from that normally given in textbook treatments of the wave packet formulation of gas phase scattering. Finally, an example approximate version of the formalism (namely the energy sudden) is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452158
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A numerically exact full wave packet approach to molecule–surface scattering (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6519-6524 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A numerically exact spectral method for solving the time-dependent Schrödinger equation in spherical coordinates is described. The angular dependence of the wave function is represented on a two-dimensional grid of evenly spaced points. The fast Fourier transform algorithm is used to transform between the angle space representation of the wave function and its conjugate representation in momentum space. The time propagation of the wave function is evaluated using an expansion of the time evolution operator as a series of Chebyshev polynomials. Calculations performed for a model system representing H2 scattering from a rectangular corrugated surface yield transition probabilities that are in excellent agreement with those obtained using the close-coupling wave packet (CCWP) method. However, the new method is found to require substantially more computation time than the CCWP method because of the large number of grid points needed to represent the angular dependence of the wave function and the variation in the number of terms required in the Chebyshev representation of the time evolution operator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457367
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Application of the close coupling wave packet method to long lived resonance states in molecule–surface scattering (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6140-6149 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we describe the application of the close coupling wave packet (CCWP) method to the study of HD and H2 scattering from a Ag(111) surface. The presence of rotationally mediated selective adsorption (RMSA) resonances at low collision energies for the HD/Ag(111) system requires that the scattering wave function be propagated for extremely long times to allow the resonant states to decay. A new procedure is presented for obtaining both the magnitude and phase of the S-matrix elements from the scattered wave packet which drastically reduces the size of the spatial grid required. Both the transition probabilities and collision lifetimes obtained from CCWP calculations are in excellent agreement with those predicted by the CC method, demonstrating that both the moduli and phases of S-matrix elements can be obtained over a range of collision energies from the propagation of a single wave packet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452768
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Molecule–corrugated surface scattering calculations using the close coupling wave packet method (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2441-2442 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Numerically exact quantum calculations for scattering of N2 off a model corrugated rigid lattice are reported. The computations were done using the recently developed close coupling-wave packet method for treating quantum scattering. Results for all energies in the range 0.010–0.040 eV are obtained from a single wave packet propagation. The calculations included even N2 rotor j states j=0–12, all mj's, and sufficient grid points to describe diffraction states −8≤m≤8, −4≤n≤4, for a total of 13 923 channels. The computations, which required a total of 230 minutes of computer time, were carried out on the CRAY2 supercomputer at the University of Minnesota Supercomputer Center under National Science Foundation support.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452093
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Body frame close coupling wave packet approach to gas phase atom–rigid rotor inelastic collisions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 241-250 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The close coupling wave packet (CCWP) method is formulated in a body-fixed representation for atom–rigid rotor inelastic scattering. For total J〉jmax the computational cost of propagating the coupled channel wave packets in the body frame scales approximately as N3/2 where N is the total number of channels. For large numbers of channels, this will be much more efficient than the space frame CCWP method previously developed which scales approximately as N2 under the same conditions. Timing results are reported for a model system for 25, 64, 144, 256, and 969 channels. The calculations were run with total J=30 and with parameters corresponding to a heavy diatom. The results for some representative transitions are compared to the identical transitions obtained using the space frame formalism. For all values of N, the body frame computations ran faster than the corresponding ones using the space frame, with the ratio increasing to a value of 4.5 for 969 channels. This is a significant improvement which will continue to increase with N, encouraging us to believe that the body frame CCWP method will prove practical for calculating scattering information for more realistic inelastic and reactive systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456526
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Quantum oscillations in rotationally inelastic molecule–surface scattering: Energy dependence of transition probabilities (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3925-3926 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Exact quantum mechanical and quasiclassical trajectory results for rotationally inelastic N2 -corrugated surface collisions are compared over the energy range 0.01–0.04 eV. It is found that the degeneracy averaged, diffraction summed, rotationally inelastic transition probabilities display quantum oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454870
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Sudden representation and sudden approximation quantal generalized master equation (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 1750-1757 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The application of the sudden approximation in the derivation of a quantal generalized master equation (GME) is examined. Two different types of physical systems are considered. One is a composite system comprised of a fast primary system and slow bath compared to the time the former is coupled to the latter. The other is a composite system comprised of a slow primary system and fast bath. The resulting sudden GME's for both cases contain non-Markovian memory kernels. In the second case, the memory kernel can be further approximated by a Markovian form. The resulting Markovian-sudden GME is identical to the GME obtained by using the adiabatic elimination method for removing the (fast) stochastic bath coordinates. Using a representation of the Schrödinger propagator for the density operator analogous to the recently developed (energy) sudden representation of the Schrödinger propagator for the wave function, the exact GME is recast into a form such that when the memory kernel and the inhomogeneity term of the equation are expanded in a perturbation series, the zeroth order equation is in the sudden approximation form. Finally, a harmonic oscillator coupled linearly to a bath of harmonic oscillators is used as an illustration. The behavior of the bath correlation functions in the Markovian and the sudden limits is examined. The reduction of the exact GME to the sudden approximation form is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449363
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Path integral approach to multiparticle systems: The sudden representationf a@f ) (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 680-687 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The recently developed (energy) sudden representation of the Schrödinger propagator is examined in conjunction with the path integral method. The perturbation expansion of the propagator in this representation (with the sudden approximation as the zeroth order term) is easily understood using Feynman diagrams. The zeroth order term is a form involving only sudden paths (i.e., paths resulting from the sudden approximation). Each higher order term is a series of sudden paths which are connected to one another due to the nonsudden effects of the dynamics. The sudden representation, and in particular its perturbation expansion, is also used to study the bath effects in many body systems which are expressed in the form of influence functionals in the path integral formalism. In our treatment, the bath coordinates are assumed to be the slow coordinates. The zeroth order (sudden approximation) influence functionals are expressed in a very simple form; they involve only an ordinary integral over the bath coordinates. Finally, to illustrate the approach, a harmonic oscillator coupled linearly to an unspecified primary system is used as a simple model bath. The reduction of the exact influence functional to the sudden approximation form is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449537
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    A study of the quantal time delay matrix in collinear reactive scattering (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 4500-4508 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Eisenbud–Wigner time delay matrix is used to study the dynamics of reaction close to vibrationally adiabatic barrier energies. Maxima in the time delay are predicted and are found to be in excellent agreement with vibrationally adiabatic barrier energies determined by quantized pods. The actual time spent in the vicinity of the barriers is estimated by separating out the free particle time. This "real time'' is then used to analyze the validity of the adiabatic and sudden approaches to reactive scattering in the 3D H+H2 and D+H2 reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448704
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...