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  • 1990-1994  (24)
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  • 1
    Electronic Resource
    Electronic Resource
    Comment on: Resonance structure in the energy dependence of state-to-state differential scattering cross sections for the D+H2(v,j)→HD(v',j')+H reaction (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5356-5357 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: During quantum reactive scattering calculations for the title reaction a pronounced resonance structure became apparent in the energy dependence of state−to−state differentialscattering calculations. This resonance structure is explained.(AIP)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459658
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    New method in time-dependent quantum scattering theory: Integrating the wave function in the interaction picture (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 324-331 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new approach for solving the time-dependent wave function in quantum scattering problem is presented. The conventional wave packet method, which directly solves the time-dependent Schrödinger equation, normally requires a large number of grid points since the Schrödinger picture wave function both travels and spreads in time. Also, since the Schrödinger picture wave function oscillates in time with frequency ω=E/(h-dash-bar), a very small time increment is required to integrate the Schrödinger equation, especially for high energy collisions. The new method presented in this paper transforms the Schrödinger picture wave function into the interaction picture and carries out the integration in it. The new approach is superior to conventional one in that (1) a smaller numerical grid is required due to the localized nature of the interaction picture wave function, since it is not a traveling wave and does not spread appreciably in coordinate space, and thus behaves like a bound state wave function. (2) The interaction picture wave function varies slowly with time and is essentially independent of energy, permitting the use of a large time increment in the numerical integration. Because of these two features in this new approach, we are able to integrate the time dependent wave function once and obtain an accurate S matrix over a wide range of energy efficiently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458433
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Photodissociation and continuum resonance Raman cross sections and general Franck–Condon intensities from S-matrix Kohn scattering calculations with application to the photoelectron spectrum of H2F−+hν→H2+F, HF+H + e− (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1811-1818 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is shown how the S-matrix version of the Kohn variational method for quantum scattering can be readily adapted to compute matrix elements involving the scattering wave function and also matrix elements of the scattering Green's function. The former of these quantities is what is involved in computing photodissociation cross sections, photodetachment intensities from a bound negative ion to a neutral scattering state, or the intensity of any Franck–Condon transition from a bound state to a scattering state. The latter quantity (i.e., a matrix element of the scattering Green's function between two bound states) gives the resonance Raman cross section for the case that the intermediate state in the Raman process is a scattering state. Once the basic S-matrix Kohn scattering calculation has been performed, it is shown that little additional effort is required to determine these quantities. Application of this methodology is made to determine the electron energy distribution for photodetachment of H2F− to F+H2, HF+H. Resonance structure in the J=0 reaction probabilities is seen to appear in the electron energy distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458063
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Full-dimensional time-dependent treatment for diatom–diatom reactions: The H2+OH reaction (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1146-1156 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Extending our previous studies for the H2+OH reaction in five mathematical dimensions (5D) [J. Chem. Phys. 99, 5615 (1993); 100, 2697 (1994)], we present in this paper a full-dimensional (6D) dynamics study for the title reaction. The 6D treatment uses the time-dependent wave-packet approach and employs discrete variable representations for three radial coordinates and coupled angular momentum basis functions for three angular coordinates. The present 6D study employs an energy projection method to extract reaction probabilities for a whole range of energies from a single wave-packet propagation, while previous studies produced only energy-averaged reaction probability from a single wave-packet propagation. The application of the energy-projection method allows us to efficiently map out the energy dependence of the reaction probability on a fine grid which revealed surprisingly sharp resonancelike features at low collision energies on the Schatz–Elgersma potential surface. Our calculation shows that the potential-averaged 5D treatment can produce reaction probabilities essentially indistinguishable from the full-dimensional result. We also report initial state-selected reaction cross sections and rate constants which are in good agreement with our previous calculations. The effect of OH vibration on H2+OH reaction is examined in the present study and our calculation shows that the OH vibration can enhance the rate constant by about a factor of 1.7 in good agreement with the experimental estimate of about 1.5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467808
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Quantum dynamical studies for photodissociation of H2O2 at 248 and 266 nm (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 5631-5638 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new quantum mechanical study on UV photodissociation of H2O2 at 248 and 266 nm using a 2D fit to the Schinke–Staemmler's (SS) potential energy surface (PES) [Chem. Phys. Lett. 145, 486 (1988)] is reported. The rotational distributions of the product OH on both the A˜ and B˜ surfaces are found to be considerably hotter than those obtained in a previous quantum study [J. Chem. Phys. 98, 6276 (1993)] using an empirical PES with a very weak dependence on the torsional angle φ. The new calculation shows that the rotation distributions in both the A˜ and B˜ states are Gaussianlike with a maximum at j=8 on the A˜ surface and at j=9 on the B˜ surface at 248 nm. Similar distributions are found at 266 nm, but with the maximum shifting lower by approximately one quanta in both the A˜ and B˜ states. The dissociation preferentially produces OH rotations with a high j1∼j2 correlation. These conclusions are in excellent agreement with the classical calculation of Schinke–Staemmler at 193 nm photolysis. Although the j distribution (rotation of OH) is similar on both surfaces, the j12(j↘12=j↘1+j↘2) distribution, which reflects the vector correlation of j↘1 and j↘2, is quite different on two surfaces. Our calculation shows that the A˜ surface gives rise to more bending excitation than the B˜ surface, reflected by a hotter j12 distribution on the A˜ surface. The A˜ and B˜ state branching ratio of H2O2 is also evaluated at 248 and 266 nm photolysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467130
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Accurate quantum calculations for H2+OH→H2O+H: Reaction probabilities, cross sections, and rate constants (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 2697-2706 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Following a previous Communication [J. Chem. Phys. 99, 5615 (1993)], which reported several initial state-selected total reaction probabilities for the title reaction for J=0, we present in this paper the methodologies of the previous calculation and show results of new calculations. In particular, the present calculations are extended to all angular momentum J(approximately-greater-than)0 and obtained reaction cross sections for a range of energies using the centrifugal sudden (CS) approximation. The computed cross sections are used to obtain the state-specific thermal rate constants for both the ground and the excited vibrations of H2. The dynamics calculation, in which the nonreactive OH bond is frozen, includes explicitly five degrees of freedom in the time-dependent quantum dynamics treatment. The comparison of the present accurate cross sections with other approximate theoretical calculations shows discrepancies. The computed rate constants (from the ground rotation state) are larger than experimental measurements at low temperatures, the v=0 rate is larger than the corresponding experimental rate by a factor of 1.8, and the ratio of v=1 to v=0 rate is a factor of 4.8 greater than the experimental ratio at 300 K. The calculated reaction rates are also compared to those of other theoretical calculations and the differences are discussed in the text.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466464
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Quantum reactive scattering with a deep well: Time-dependent calculation for H+O2 reaction and bound state characterization for HO2 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3671-3678 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show in this paper a time-dependent (TD) quantum wave packet calculation for the combustion reaction H+O2 using the DMBE IV (double many-body expansion) potential energy surface which has a deep well and supports long-lived resonances. The reaction probabilities from the initial states of H+O2(3Σ−g) (v=0–3, j=1) for total angular momentum J=0 are obtained for scattering energies from threshold up to 2.5 eV, which show numerous resonance features. Our results show that, by carrying out the wave packet propagation to several picoseconds, one can resolve essentially all the resonance features for this reaction. The present TD results are in good agreement with other time-independent calculations. A particular advantage of the time-dependent approach to this reaction is that resonance structures—strong energy dependence of the reaction probability—can be mapped out in a single wave packet propagation without having to repeat scattering calculations for hundreds of energies. We also report calculations of some low-lying vibrational energies of the hydroperoxyl radical HO2(2A‘) and their spectroscopic assignments. The vibrational frequencies of HO2(2A‘) on the DMBE IV potential energy surface are lower than experimental values, indicating the need to further improve the accuracy of the potential energy surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467551
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Symmetry and rotational orientation effects in dissociative adsorption of diatomic molecules on metals: H2 and HD on Cu(111) (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1555-1563 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Following two previous quantum dynamics studies [J. Chem. Phys. 97, 6784 (1992); 99, 1373 (1993)], we present in this paper a more thorough investigation of the symmetry and rotational orientation effects in dissociative chemisorption of diatomic molecules on metals. Specifically, we extended our theoretical studies to calculate the sticking coefficients for H2 and its isotopomer HD on Cu from all angular momentum states (up to j=8). Our calculation shows a strong dependence of the dissociation probability P(jm) on both j and m rotation quantum numbers, and the increases of P(jm) are closely correlated with the increase of the quantum number m in a given j manifold. Also the dissociation of the diatomic rotational states whose quantum numbers satisfy j+m=odd is forbidden at low energies for the homonuclear H2 due to the selection rule. The present study provides further evidence that the effect of diatomic rotation on adsorption mainly arises from the effect of rotational orientation (m dependence) as found in previous studies. This m dependence predicts that at low kinetic energies, the degeneracy-averaged dissociation probability of hydrogen on Cu increases monotonically as the rotation quantum number j increases. However, at high kinetic energies, the adsorption probability first decreases as j increases from 0 to about 4–5 before increasing as j further increases above 4–5. The latter behavior is consistent with a recent experimental measurement by Michelsen et al. of the mean kinetic energy of the rotational states of D2 desorbed from Cu(111).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467778
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Progress of basis optimization techniques in variational calculation of quantum reactive scattering (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6047-6054 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper describes several efficient basis optimization methods that we have developed in the application of S-matrix Kohn variational method to quantum reactive scattering. Specifically, we employ a minimum-K body-fixed representation combined with the use of quasiadiabatic basis functions for the expansion of the full reactive scattering wave function. This new basis function approach significantly reduces the size of the "larger'' matrix of the final linear algebraic equation in the calculation of reaction cross sections. The accuracy of the calculation can be easily controlled by systematically increasing or decreasing the values of two parameters Kmax and α, and convergence to the full basis set results can be reached. Numerical test calculations are carried out for the 3D H+H2 reaction for the total angular momentum J=10 and for the 3D F+H2 reaction for J=0, 1, and 2. These calculations demonstrate that our basis optimization approach is very efficient for computing reaction cross sections. Since variational scattering calculations are ultimately limited by the size of the basis set, our method is a stride forward in the applications of variational approach to quantum reactive scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460442
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    An efficient time-dependent Golden Rule treatment for three-dimensional vibrational predissociation of helium diiodide (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 1575-1578 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100183a017
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    Paper (German National Licenses)
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