Library

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
  • 11
    Electronic Resource
    Electronic Resource
    Vibrational predissociation of HF dimer in νHF=1: Influence of initially excited intermolecular vibrations on the fragmentation dynamics (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4382-4389 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical study of the influence of excited intermolecular vibrations on the total and partial decay widths of HF dimer is reported. Vibrational predissociation (VP) lifetimes and rotational state distributions of HF fragments were calculated for various quasibound states of (HF)2, corresponding to combinations of the intermolecular stretching (ν4) and bending (ν5) vibrations with the "free'' (ν1) and "bonded'' (ν2) HF stretch fundamentals, for total angular momentum J=1, K=0. The calculations were performed on an ab initio six-dimensional potential energy surface of Quack and Suhm, using a quantum four-dimensional golden rule methodology. The VP lifetimes and product rotational distributions exhibit pronounced dependence on the type of the initially excited intermolecular vibration of HF dimer. The energy deposited in the ν4 intermolecular stretch evolves into the translational energy of the fragments. Excitation of the ν5 intermolecular bending vibration, combined with the ν1 fundamental, is transferred to the product rotational energy. This is in good agreement with the experimental results of Bohac and Miller. We also found that in conjunction with the ν2 fundamental, most of the ν5 bending vibrational energy emerges in the translational energy of the products. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469487
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Quantum adsorption dynamics of a diatomic molecule on surface: Four-dimensional fixed-site model for H2 on Cu(111) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6280-6289 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We presented a detailed quantum dynamics study for dissociative adsorption of H2 at different sites of Cu(111) surface to investigate the effect of surface corrugation and site specificity. The theoretical study employed a four-dimensional (4-D) "fixed-site'' model, in which the lateral coordinates (X,Y) of the center of mass of the diatom are fixed at the impact site, but the remaining four degrees of freedom are explicitly treated in quantum calculations. The inclusion of the azimuthal angle φ in the present 4-D model is a significant step forward in theoretical studies beyond the 3-D "flat surface'' model. This 4-D "fixed-site'' model allows us to investigate explicitly the local corrugation effect that was not possible using the 3-D flat-surface model. We incorporated the latest ab initio data of Hammer et al. in constructing the LEPS potential energy surface, which gives the lowest dissociation barrier over the bridge site. 4-D dynamics calculations are performed in the present study to mimic a normal incidence of H2 at three symmetric sites on Cu(111): bridge, atop, and center sites with the corresponding rotation symmetries. Our results show that a hydrogen impact at a high symmetry site (six-fold atop site) shows little corrugation effect while impact at low symmetry site (two-fold bridge site) shows a large corrugation effect. In particular, our calculation shows that the inclusion of surface corrugation preserves the strong rotational orientation effect observed in flat-surface model calculations. The effect of homonuclear symmetry persists at high symmetry atop site, and to a lesser degree at a low symmetry bridge site. The contour plot of the wavefunction in the current 4-D model shows explicitly that hydrogen atoms following the dissociation of H2 over the bridge site do not settle at the neighboring center site, but migrate to the next available center site. Our study demonstrated that the 4-D fixed-site model is very useful in investigating surface corrugation and molecule site specificity in model-surface reactions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469074
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Quantum calculations of reaction probabilities for HO + CO→ H + CO2 and bound states of HOCO (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 6512-6519 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A time-dependent (TD) quantum wavepacket calculation of reaction probabilities is reported for the reaction HO + CO → H + CO2 for total angular momentum J=0. The dynamics calculation employs the potential-averaged five-dimensional model (PA5D) and is made possible by using a normalized angular quadrature scheme to minimize the requirement for computer memory. Reaction probabilities are obtained from the ground state as well as rotationally excited state in either one of the reactant diatoms. Strong resonances are found in the present study and calculated reaction probabilities are dominated by many narrow and overlapping resonances. These features are in qualitative agreement with several lower dimensional quantum dynamics studies. However, quantitative comparison of the present result with previously reported quantum calculations, including a recent planar four-dimensional (4D) calculation of Goldfield et al., shows that our calculated reaction probabilities are much smaller than those found in reduced dimensionality calculations. We also found reaction probability to be more sensitive to the rotational motion of CO than of HO. In addition to reaction probabilities, the bound state calculation for the stable intermediate complex HOCO has also been carried out and energies of several low-lying vibrational states are obtained. The potential energy surface (PES) of Schatz–Fitzcharles–Harding (SFH) is used in all the calculates presented in this paper. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470377
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Exact full-dimensional bound state calculations for (HF)2, (DF)2, and HFDF (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2315-2325 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Detailed results of the converged full-dimensional 6D quantum calculations of the vibrational levels of (HF)2, (DF)2, and HFDF, for total angular momentum J=0, are presented. The ab initio 6D potential energy surface by Quack and Suhm was employed. This study provides a comprehensive description of the bound state properties of the HF dimer and its isotopomers, including their dissociation energies, frequencies of the intermolecular vibrations, tunneling splittings, and extent of wave function delocalization. Quantum number assignment of the calculated eigenstates by plotting different cuts through the wave functions worked rather well for (HF)2, but proved to be much harder for (DF)2 and HFDF, indicating stronger vibrational mode mixing in these species. The ground-state tunneling splitting for the HF dimer from our exact 6D calculations, 0.44 cm−1, is very close to that from a previous 4D rigid-rotor calculation, 0.48 cm−1 [J. Chem. Phys. 99, 6624 (1993)]. This is in disagreement with the result of a recent 6D bound state calculation for (HF)2 by Necoechea and Truhlar, which gave a ground-state tunneling splitting a factor of 3.7 times larger than the 4D result. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468719
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Noise-free spectrum for time-dependent calculation of eigenenergies (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 1491-1497 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We explored and studied the use of several energy spectra for numerical applications in time-dependent calculation of bound state energies. Although all three types of the spectrum we studied, Sinc, Lorentzian, and Gaussian, approach the δ-function limit in the infinite time limit, their numerical properties at finite time limit are quite different. Our analysis, supported by numerical example, shows that by using Gaussian or Lorentzian spectrum, one can eliminate all the "noises'' (extra peaks) present in the standard Sinc spectrum based on Fourier transform of autocorrelation function. The use of these two spectra enables us to obtain unambiguously all eigenvalues as long as the corresponding eigenfunctions have overlaps, albeit small, with the initial wavepacket. These small-component eigenstates are normally buried under the spectral "noise'' in the standard Sinc spectrum. The Gaussian spectrum offers better resolution than Lorentzian spectrum and is recommended for use in time-dependent calculation of eigenenergies. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469770
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    A time-dependent approach to flux calculation in molecular photofragmentation: Vibrational predissociation of HF–DF (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 124-132 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present in this paper a time-dependent approach to the calculation of photofragmentation dynamics using the flux formulation. The method is essentially a time-dependent version of the flux formulation for photodissociation calculation recently pursued by Manolopoulos and Alexander. In the present approach, the partial decay width of photofragmentation is obtained by calculating the flux at a given surface using a time-dependent method. This particular time-dependent approach for photofragmentation has two principal advantages. First, it is superior in computational scaling: CPU time ∝Nα(α〈2) vs N3 in standard time-independent propagation method. Second, it is quite straightforward to handle the photofragmentation process involving rearrangement with the application of optical potentials. In addition, no bound state projection is necessary using the time-dependent flux method, which is required using the time-dependent golden rule method. This time-dependent method is applied to the calculation of decay width for vibrational predissociation of hydrogen-bonded HFDF, and the computed lifetime are compared with the recent experimental measurement of Farrell and Nesbitt. We also present the results of the full dimensional (6D) calculation of bound state energies for the HFDF complex. The exact dissociation energies are calculated to be 1057.33 cm−1 for (HF)2, 1166.6 cm−1 for (DF)2, 1142.7 cm−1 for HF–DF, and 1078.4 cm−1 for DF–HF. All theoretical calculations have used the SQSBDE potential energy surface due to Quack and Suhm. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469382
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Quantum dynamics study of the reaction HD+OH→H+DOH, D+HOH (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 7400-7408 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Accurate time-dependent (TD) quantum wavepacket calculations are reported for the combustion reaction HD+OH. Due to the lack of symmetry, the HD+OH reaction has roughly twice the number of channels of the corresponding H2+OH reaction and produces two distinguishable products–HOH and HOD. In order to make the TD calculation possible on workstations with limited memories, we employed a normalized quadrature scheme in the wavepacket propagation by the split-operator propagator. The normalized quadrature scheme eliminates the need to store large matrices during the wavepacket propagation while preserving the unitarity of the split-operator propagator and producing numerically stable results. This approach made TD dynamics calculations possible on small-memory workstations for the title reaction and for other polyatomic reactions. Reaction probabilities, cross sections, rate constants, and reaction branching ratios are reported in this paper for the title reaction. The observed strong dependence of the reaction probabilities on the reactive HD rotation and the relative weak dependence on the nonreactive OH rotation are explained in terms of a steric effect. The isotope effect in the branching ratio is examined and physical explanation is given for the observed branching ratio at low and high kinetic energies. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469052
    Library Location Call Number Volume/Issue/Year 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...