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
  • 1
    Electronic Resource
    Electronic Resource
    Exploring the transition state for the Li+HF→LiF+H reaction through the A←X absorption spectrum and X←A stimulated emission pumping (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3440-3448 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The A(2 2A′) first excited electronic state of LiHF has been calculated (about 3300 points at MRDCI level) and an analytical fit of the global potential energy surface is presented. The A←X absorption spectrum is simulated at 10 K between 9000 and 13 000 cm−1, what involves the calculation of excited bound states for moderately high total angular momentum. These quasibound levels of the A state can only decay by electronic predissociation (EP) towards the X ground state, since the spontaneous radiative emission is considered to be very slow. The decay of such states has been estimated using a perturbative approach and it is found that LiF products are produced with a high efficiency (〉80%). The X←A stimulated emission pumping spectra is simulated for several initial quasibound levels. These spectra allow the examination of the reaction dynamics specially near the transition state region, and the first photon excitation may act as a rotational filter, reducing the problem of the partial wave average involved in reactive collisions. The high reaction efficiency of this last process is also discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1340564
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    State-to-state reaction probabilities using bond coordinates: Application to the Li+HF(v, j) collision (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 1781-1794 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this work we present a time-dependent method to evaluate state-to-state reaction probabilities, based on bond coordinates and an adapted body-fixed frame. Such a method is expected to be rather efficient to describe A+BC→AB+C reactive collisions. In addition, the apparent complexity of the Hamiltonian expressed in these coordinates is reduced when applied to a wave packet represented in grids for the internal coordinates. The efficiency of this method as compared to the use of the most adapted Jacobi coordinates increases as the masses of the satellite atoms approach that of the heavier central atom and, what may be more important, avoids the problems associated with the singularities of the radial kinetic terms in the region of configuration space of interest. This method is used to study the Li+HF(v=0,1,j=0,J=0) reactive collision and the structure of the final state distribution of the LiF products is interpreted in terms of transition state resonances. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481982
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The vibrational structure of H+4 and D+4 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5725-5732 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A potential energy surface (PES) for the H+4 system which is a fit to local, high quality ab initio multiple reference single and double excitations configuration interaction (CI) calculations (142 data points) is reported. The potential energy surface obtained here has been calculated by maintaining H+3 as a core in its equilibrium geometry and moving the remaining hydrogen atom around it (three-dimensional potential energy surface). The new surface supposes an improvement on the preceding potential energy surfaces considering both the basis set size and the ab initio method used here. The energy minimum of the potential presented here has been found to be about 2.5 kcal/mol lower than those obtained in previous studies, indicating that H+4 and D+4 are more stable ions than previously believed. A three-dimensional vibrational kinetic energy operator in internal coordinates without singularities has been derived. Energy and wave functions of the vibrational levels of the dissociating hydrogen in H+4 and D+4 systems have been calculated by using the derived potential and kinetic energy operators and integrating the vibrational Hamiltonian with the normal coordinates finite elements method. The vibrational states with energies below the new dissociation limit are reported and characterized, giving a more complete description of the vibrational structure. The number of bound vibrational levels obtained here is 7 for H+4 and 24 for D+4. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469303
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Accurate global fit of the H4 potential energy surface (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4004-4010 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A global potential energy surface (PES) for the adiabatic ground state of the H4 system which fit published ab initio data [Boothroyd, et al. J. Chem. Phys. 95, 4331 (1991)] at a quantitative level has been obtained (root-mean-square error about 2 mhartree or 1–2 kcal/mol), and without any quantity of ad hoc character, preserving the accuracy of the ab initio points. The global fitting procedure used here is an extension of the corresponding procedure for triatomic systems including the functional form previously proposed by the authors. The global H4 PES obtained here is totally symmetric with respect to permutations of the hydrogen atoms and satisfies the criteria needed to be used in scattering calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467518
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Transition state spectroscopy via infrared excitation of Li(centered ellipsis)HF and Li(centered ellipsis)DF van der Waals precursors (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6712-6723 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoinitiated reactions after infrared excitation from the LiHF and LiDF complexes in the reactant valley are studied as an extension of a recent communication by Paniagua et al. [J. Chem. Phys. 109, 2971 (1998)]. For LiHF two broad bands, associated to Δv=1 and 2 transitions, are obtained at which the probability of forming LiF products is very high, 〉90%. For LiDF the Δv=1 band consists of several narrow resonances, and some of them are supported by the barrier separating reactant and product valleys. Even at these resonances the reaction probability is relatively high, starting at a value about 30% and increasing rapidly to 〉90% with increasing energy. This implies the tunneling through the barrier. The reason for the high efficiency in the photoinitiated reaction is that the main excitation corresponds to the HF (or DF) stretch within the complex, which is the "active" mode for the reaction in agreement with the presence of a late barrier. These results are very different from those obtained in Li+HF or Li+DF collisions at the same total energies, the reaction probabilities being much lower in these latter since the excitation of the HF (DF) mode is unlikely to occur during the collision. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480040
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Global nine-dimensional potential energy surface for the H5 system. II. Fit to an analytical expression (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7796-7801 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A global nine-dimensional potential energy surface (GPES) for the adiabatic ground state of the H5 system which fits the ab initio data, reported in the previous paper of this series, has been obtained (root-mean-square error 2.2 kcal/mol). The global fitting procedure is an extension of the corresponding procedure for triatomic and tetra-atomic systems including the functional form previously proposed by the authors. The H5 GPES obtained here is totally symmetric with respect to permutations of the hydrogen atoms and satisfies the criteria needed to be used in scattering calculations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478688
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Global nine-dimensional potential energy surface for the H5 system. I. Ab initio multiple reference single and double excitation configuration interaction computations (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7789-7795 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ground-state adiabatic potential energy surface was computed for 2836 conformations of H5, using a multiple reference single and double excitation configuration interaction program and an extended basis set. The transition state obtained is that of a pentagon with D5h symmetry. We find the energy barrier to lie at 81 kcal/mol within ±1 kcal/mol if a multireference Davidson's correction is employed, while the De(H2) at this level was 109 kcal/mol. The calculations presented here clearly show the energy of H5 in D5h symmetry to be 28 kcal/mol below the dissociation energy of H2, and therefore a bimolecular mechanism, in the presence of hydrogen atoms, could indeed be considered for the exchange process: H2+D2+H→2HD+H. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478687
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Transition state spectroscopy on the Li-HF system (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 2971-2974 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The transition state region of the Li-HF system is theoretically studied via infrared excitation of the ground state of the complex in the reactant valley. The absorption spectrum shows intense peaks for which LiF is produced with high efficiency ((approximate)90%), while the reaction has a very low cross section during the collision at the same energies. The reason is that the resonances reached through optical excitation are in the vicinity of the transition state. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476886
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Quantum study of the Li+HF→LiF+H reaction (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 10085-10095 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this work we present a new global fit for the potential energy surface of the LiFH system. This fit is an improvement of a recently published one [Aguado et al., J. Chem. Phys. 106, 1013 (1997)] for which more ab initio points have been calculated (from 644 to 2323). The reaction dynamics is studied using a time dependent treatment in reactant Jacobi coordinates in a body-fixed frame in which the internal coordinates are represented on a grid while Eulerian angles are described in a basis set. The centrifugal sudden approach is tested for total angular momentum J=5 and used to calculate the reaction cross section. The reaction cross section shows oscillations as a function of kinetic energy. This is a consequence of strong interference effects between reactant and product channels and is in agreement with the recent experimental data. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474145
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Potential energy surface and wave packet calculations on the Li+HF→LiF+H reaction (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1013-1025 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this work an analytic fit of previous ab initio points [Aguado, Suárez, and Paniagua, Chem. Phys. 201, 107 (1995)] on the potential energy surface of the LiFH system is presented and the reaction dynamics is studied using a time-dependent treatment based on local coordinates. Three-dimensional wave packet calculations performed for zero total angular momentum indicate that the reactivity for the HF reactant in its ground vibrational state is quite low, in contradiction with previous dynamical calculations using different potential energy surfaces. The differences with previous potential energy surfaces are further analyzed using a bidimensional approach. Finally, the effect of the initial vibrational excitation of the HF reactant on the reactivity is studied using the bidimensional approach. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473185
    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...