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  • 1
    Electronic Resource
    Electronic Resource
    Reduced partial dissociation cross sections for a molecule photodesorbed from a surface (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5712-5721 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An implementable formalism is given for computing reduced partial cross sections for photodissociation into final internal fragment states of selected primary modes of motion, but unresolved (i.e., summed over all possible outcomes) with respect to other secondary modes. For concreteness, we focus on the case of photodesorption of a diatomic molecule from a crystal lattice. Using time-dependent wave-packet propagation techniques, numerical illustration is presented for a simplistic model of carbon monoxide initially bound to monoatomic carbon and aluminum crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458502
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  • 2
    Electronic Resource
    Electronic Resource
    Time-dependent Hartree wave packet dynamical techniques for computation of electronically excited state optical spectra of many-body quantum systems (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4015-4030 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An approximate solution technique for computing spectra of many-body molecular systems is proposed. We focus for concreteness on 0 K electronic absorption and emission spectra. From a time-domain perspective, it is necessary to propagate a well-defined initial Schrödinger wave packet on a specified potential energy surface in order to extract such spectra. In order to perform this task for systems with many degrees of freedom, we investigate the utility of a time-dependent Hartree factorization, in which the wave packet for the complete system is variationally factorized into a product of wave packets of smaller dimensionality. This method is shown to be both flexible and reliable for prototypical model systems associated with the physical problem of impurity spectra in host crystals. Successful application is made to a recently measured emission spectrum of I2 embedded in an argon matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455812
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  • 3
    Electronic Resource
    Electronic Resource
    Time-of-flight spectra of a particle scattering from a collinear harmonic lattice at finite temperature (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5297-5306 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new formalism is developed for computing the time-of-flight spectrum of a particle scattering from a collinear harmonic lattice prepared at finite temperature. We use a time-domain transcription to construct an S-matrix formalism that can be easily implemented via Gaussian wave packet dynamics. Numerical results are presented for a particle scattered from a lattice containing 100 oscillators at several temperature values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458534
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  • 4
    Electronic Resource
    Electronic Resource
    Variational solutions for the thermal and real time propagator using the McLachlan variational principle (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6570-6577 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new approximation to the propagator is presented. The approximation as applied to the thermal propagator (coordinate space density matrix) is obtained by using an analog of the McLachlan variational principle for the solution of the Bloch equation. The approximation as applied to the real time propagator is obtained by using the McLachlan variational principle for the solution of the time-dependent Schrödinger equation. The approximate coordinate space density matrix has the same functional form of the high temperature limit of the density matrix, while the approximate real time propagator has the same functional form as the short time propagator. We present numerical results for the thermal propagator for several test systems and compare these results to previous work of Zhang, Levy, and Freisner [Chem. Phys. Lett. 144, 236 (1988)], Mak and Andersen [J. Chem. Phys. 92, 2953 (1990)], and Cao and Berne [J. Chem. Phys. 92, 7531 (1990)]. We also present numerical results for the approximate real time propagator for several test systems and compare to the exact results and results obtained by Gaussian wave packet propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467066
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  • 5
    Electronic Resource
    Electronic Resource
    Time-of-flight spectra and angular observables for ultraviolet photodesorption of molecules from surfaces (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 8977-8990 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show how to efficiently compute time-of-flight spectra and angular distributions associated with ultraviolet photodesorption phenomena using quantum wave packet simulations. Our method can be applied to adsorbates with internal vibrational and rotational degrees of freedom, and includes effects of (finite temperature) lattice vibrations on the photodesorption dynamics. Numerical applications to photodesorption of (a) a vibrating diatom from a collinear chain of harmonic oscillators and (b) a rigid rotor from the (100) face of LiF demonstrate the utility of our approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461229
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum Control of Molecular Dynamics: The Strong Response Regime (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 13736-13747 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100037a022
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  • 7
    Electronic Resource
    Electronic Resource
    Detection and control of molecular quantum dynamics (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 14949-14958 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100041a008
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  • 8
    Electronic Resource
    Electronic Resource
    Quantum control of dissipative systems: Exact solutions (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 5239-5248 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Optimal quantum control theory, which predicts the tailored light fields that best drive a system to a desired target, is applied to the quantum dissipative dynamics of systems linearly coupled to a Gaussian bath. To calculate the material response function required for optimizing the light field, the analytical solution is derived for the two-level Brownian harmonic oscillator model and the recently developed method for directly simulating the Gaussian force is implemented for anharmonic Brownian oscillators. This study confirms the feasibility of quantum control in favorable condensed phase environments and explores new quantum control features in the presence of dissipation, including memory effects and temperature dependence. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473522
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  • 9
    Electronic Resource
    Electronic Resource
    A variational centroid density procedure for the calculation of transmission coefficients for asymmetric barriers at low temperature (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3430-3435 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The low temperature behavior of the centroid density method of Voth, Chandler, and Miller (VCM) [J. Chem. Phys. 91, 7749 (1989)] is investigated for tunneling through a one-dimensional barrier. We find that the bottleneck for a quantum activated process as defined by VCM does not correspond to the classical bottleneck for the case of an asymmetric barrier. If the centroid density is constrained to be at the classical bottleneck for an asymmetric barrier, the centroid density method can give transmission coefficients that are too large by as much as five orders of magnitude. We follow a variational procedure, as suggested by VCM, whereby the best transmission coefficient is found by varying the position of the centroid until the minimum value for this transmission coefficient is obtained. This is a procedure that is readily generalizable to multidimensional systems. We present calculations on several test systems which show that this variational procedure greatly enhances the accuracy of the centroid density method compared to when the centroid is constrained to be at the barrier top. Furthermore, the relation of this procedure to the low temperature periodic orbit or "instanton'' approach is discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470227
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  • 10
    Electronic Resource
    Electronic Resource
    Quantum control of multidimensional systems: Implementation within the time-dependent Hartree approximation (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 173-182 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The exact formulation of quantum control is now well known and sufficiently general to describe multidimensional quantum systems. The implementation of this formalism relies on the solution of the time-dependent Schrödinger equation (TDSE) of the system under study, and thus far has been limited for computational reasons to simple quantum systems of very small dimensionality. To study quantum control in larger systems, such as polyatomic molecules and condensed phases, we explore an implementation of the control formalism in which the TDSE is solved approximately using the time-dependent Hartree (TDH) approximation. We demonstrate formally that the TDH approximation greatly simplifies the implementation of control in the weak response regime for multidimensional systems. We also present numerical examples to show that the TDH approximation for the weak response case is sufficiently accurate to predict the laser fields that best drive a quantum system to a desired goal at a desired time, in systems containing more than one degree of freedom, by considering a two-dimensional quantum system and comparing the optimal fields obtained by solving the TDSE exactly to those obtained using the TDH approximation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470887
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