ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3571-3576 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new method for the calculation of bound state eigenvalues and eigenfunctions of the Schrödinger equation is presented. The Fourier grid Hamiltonian method is derived from the discrete Fourier transform algorithm. Its implementation and use is extremely simple, requiring the evaluation of the potential only at certain grid points and yielding directly the amplitude of the eigenfunctions at the same grid points.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6520-6534 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical study of the photodissociation dynamics of H2S in its first absorption band is presented. The potential energy surfaces underlying the dynamics of the breakup process have been modeled so as to reproduce the principal features of all the available experimental data. The modeling is performed using time dependent quantum dynamical methods and involves the exact numerical solution of the time dependent Schrödinger equation. The fitting of the experimental observations requires the use of potential energy surfaces corresponding to two excited electronic states. We have been able to determine two such surfaces which reproduce the observed structure in the absorption spectrum, the main features of the emission spectrum of the dissociating molecule, and the vibrational distribution of the HS photofragments. The calculations utilize a recently developed method for analyzing the wave packet dynamics to extract the partial photodissociation cross sections. The photodissociation process is found to be consistent with an initial excitation to a single excited dissociative diabatic electronic state which is weakly coupled to another, whose principal role within the first absorption band is to introduce diffuse structure into the absorption spectrum and minor perturbations to the nuclear motion. The motion on the principal dissociative electronic surface is dominated by that in the two bond stretching coordinates, while that on the surface of the second perturbing state is a one dimensional vibrational motion which may correspond to either symmetric stretching or bending, but is most probably a complex combination of both. A new method is presented for performing the time dependent quantum mechanical calculation on two coupled potential energy surfaces when the motions on both surfaces are treated in a reduced dimensionality and the dynamically active coordinates on the two surfaces are different.
    Type of Medium: Electronic Resource
    Location Call Number Expected 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 99 (1993), S. 9567-9584 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reactive scattering probabilities are computed over a wide range of collision energies for a model system based on the Li+HF→LiF+H reaction using both grid based time-dependent and time-independent quantum mechanical methods. The computations are carried out using a fixed Li–F–H angle which is chosen to be that at which the barrier to the chemical reaction is lowest. The calculated reaction probabilities for this system display many sharp features as a function of energy which are ascribed to scattering resonances. The time-independent calculations have been carried out on a very dense energy grid, thus permitting detailed comparison between time-independent and time-dependent methods (in the latter case, a single computation of the wave packet dynamics provides information on the energy dependence over a given energy range). The results show that the time-dependent calculations are capable of reproducing even the sharpest resonance features computed using the time-independent method. The time-dependent techniques are conceptually very simple and therefore easily implemented. The results presented also demonstrate that the grid based time-dependent quantum mechanical methods used here are able to describe threshold energy dependence of reaction probabilities where the exit channel kinetic energy is effectively zero. The nature of some of the resonance structures are investigated by computing the time-independent continuum wave functions at the "resonance'' energies thus mapping out the nodal structure of the wave functions. The good agreement between time-independent and time-dependent methods is shown to be maintained when a centrifugal barrier is added to the potential to simulate the effect of nonzero orbital angular momentum.
    Type of Medium: Electronic Resource
    Location Call Number Expected 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 104 (1996), S. 7927-7939 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A three-dimensional time-dependent quantum mechanical wavepacket method is used to calculate the state-to-state reaction probabilities at zero total angular momentum for the Li + HF → LiF +H reaction. Reaction probabilities starting from several different initial HF vibrational–rotational states (v=0,j=0,1,2) and going to all possible open channels are computed over a wide range of energies. A single computation of the wavepacket dynamics yields reaction probabilities from a specific initial quantum state of the reactants to all possible final states over a wide range of energies. The energy dependence of the reaction probabilities shows a broad background structure on which resonances of varying widths are superimposed. Sharp resonance features seem to dominate particularly at low product translational energies. There are marked changes in the energy dependence of the reaction probabilities for different initial or final diatom rotational quantum numbers, but it is noticeable that, for both reactants and products, odd and even rotational quantum numbers give rise to similar features. Our results clearly identify some resonance features which are present in the reaction probability plots for all product and initial states, though they appear in the form of sharp peaks in some plots and sharp dips in others. We speculate that these features arise from reactive scattering resonances which serve to redistribute the flux preferentially to particular product quantum states. The present calculations extend to higher energies than previously published time-independent reactive scattering calculations for this system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected 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 101 (1994), S. 10416-10428 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The results of time-dependent quantum mechanical calculations on the photodissociation of initially nonrotating HOCl and DOCl molecules are presented. Two photodissociation processes, 1 1A‘←X˜ 1A' and 2 1A'←X˜ 1A', are considered. The dynamics are treated in a two dimensional model with a fixed O–H distance and the dissociation process is followed in a rotating body-fixed frame with total angular momentum of J'=1. The total photodissociation spectra and product rotational distributions resulting from dissociation of HOCl and DOCl originating in a number of different vibrational states are presented over a continuous range of incident photon wavelengths in the range 140–440 nm. It is found that, for HOCl, the physically more correct treatment with J'=1 leads to a qualitatively different OH product rotational distribution than that resulting from the more usual model treatment in which both initial and excited states are assumed to possess zero total angular momentum. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected 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 101 (1994), S. 10576-10601 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential energy surfaces are computed for the four lowest electronic states of SiH+2. The surfaces provide the data necessary for the discussion of the competitive photodissociation of SiH+2 to yield either SiH+ or Si+. The study has resulted in the "discovery'' of a new conical intersection involving the ground state potential energy surface and a surface which had not previously been thought to lie at sufficiently low energies to be of interest in the photodissociation dynamics of the system. The three important conical intersections and their role in the photodissociation dynamics are discussed. Likely pathways leading from the photoexcited state created in the spectroscopic experiments to the observed SiH+ and Si+ ionic fragments are described. The ion, after initial excitation, has A˜ 2A‘ or odd symmetry and is thought to convert to a lower-lying even symmetry state (2A') by making a transition from the upper- to the lower-half of a 2Π state through the mediation of a Renner–Teller coupling mechanism. The effect of the conical intersection on the strength and qualitative nature of the coupling between these two surfaces is examined. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected 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 104 (1996), S. 563-575 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: HOCl is a closed shell system in its ground electronic state. In common with many molecules it is photodissociated to give open shell fragments. In this paper the photodissociation process HOCl(X 1A′)+hν→HOCl(2 1A′)→OH+Cl is investigated. A model is proposed to predict the OH product spin–orbit and Λ-doublet state distributions as well as the distribution of the Cl atom spin–orbit states. The model considers both the electronic structure of the system and the nuclear motion. Predictions are made not only of the individual fragment state distributions and of their dependence on total initial angular momentum and photon frequency, but also of the degree of correlation between the production of the different states of the two open shell fragments. The computed results agree with the available experiments, in particular the current theory is the first to agree with experimental findings in predicting a smoothly varying OH rotational state distribution. It is demonstrated that the model reproduces the frequency dependence of the absorption line shape as computed using more exact procedures. In the simple treatment presented here rotational transitions during the dissociation process are ignored, as is the detailed coupling of the electronic states in the asymptotic region. Some of the remaining disagreements between the current predictions and the experimental results are ascribed to these approximations in the model. It is hoped that the predictions of the correlated product state distributions will stimulate coincidence experiments on the photodissociation process. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected 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 105 (1996), S. 8615-8627 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The emission spectrum of the dissociating HOCl molecule, following the 2 1A′←X˜ 1A′ excitation, is computed using a rigorous time-dependent quantum mechanical method. The theory needed to include all the polarization and angular momentum effects within the time-dependent framework is developed and applied for the first time. Detailed predictions are made of the emission or resonance Raman spectrum of the dissociating molecule both "on resonance,'' near the peak of the first absorption band and "off resonance,'' in the tails of the band. If the exciting radiation is linearly polarized, and the direction of polarization of the emitted radiation is also measured, then four different "cases'' or geometric arrangements of the two polarization directions relative to each other can be identified. The different signals which result are computed and discussed. Expressions are given for the Raman amplitudes as a product of a dynamic and a geometric factor. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...