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
    Physisorption in a Molecular Helicoidal Cavity: Application to AlPO4-5 (1995)
    s.l. : American Chemical Society
    Langmuir 11 (1995), S. 197-203 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00001a034
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Surface diffusion of molecules physisorbed on dielectric substrates (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 688-694 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Semiempirical potential calculations are performed to determine the potential surfaces experienced by a X molecule (X=Xe,CH4,N2,CO,NH3,CH3F) adsorbed on the (100) face of dielectric substrates (MgO, NaCl) and on the (111) dense face of xenon. The diffusion mechanism of X on these surfaces is then described, within the transit time concept, as a successive jump process along the diffusion coordinate, including the statical and dynamical influence of the other molecular motions. The calculated diffusion constants can serve as a test of the surface corrugation and of the admolecule dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460336
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Rotational relaxation of a molecule trapped in a three-dimensional crystal. III. Environmental effects and relaxation channels (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4625-4635 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The stochastic classical trajectory method is used to calculate the energy relaxation of a highly excited diatomic rotor trapped in rare gas crystal at T=20 K. The friction kernels, which appear in the generalized Langevin equations characterizing the motions of the molecule and of nearest neighbor crystal atoms, are expressed in terms of the interaction potentials. The influence of the surrounding crystal on the relaxation mechanism and the efficiency of the various dissipation channels are analyzed by changing the rare gas species and by artificially switching off some channels. Within the limits of the model (classical two-dimensional rotation of the diatomic molecule, coupled on the one hand to a restricted number of first shell atoms themselves coupled to the bulk crystal and on the other hand to the other first shell atoms considered as pertaining to the bath), the results of the calculations show that, in the present case, rotational relaxation is a rapid process, over the picosecond scale, and that the local mode connected to the motions of the molecular center of mass plays a major role in the mechanism. This local mode is responsible, at short times t≤0.5 ps, for the relaxation of 95%, 75%, and 60% of the rotational energy excess in Ar, Kr, and Xe crystals, respectively.The remaining energy is then dissipated over longer times via the local mode or directly towards the crystal modes. A striking energy saturation phenomenon of the local mode is exhibited in xenon crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456752
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Dynamics for CH3F trapped in rare gas crystals and spectroscopic consequences (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1345-1357 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of CH3F molecule trapped in a rare gas crystal is determined in order to explain the infrared spectra and vibrational relaxation data which had led to controversial qualitative interpretations. It is shown that the orientational motions of the molecular axis are strongly coupled to the translational dynamics of the molecule and, in a smaller extent, to the lattice vibrations. As a first consequence, the molecular axis remains nearly anticollinear to the axis joining the molecular center of mass and the site center, and the molecule behaves as a slightly hindered rotor implying both the molecular axis and its center of mass; the spinning motion appears to be a tunneling motion which considerably narrows the splitting between the k=0 and k=1 levels. As a second consequence, the orientational signals are strongly broadened by the translational dynamics of the molecule and of the crystal. So, the only observed sharp signal with a large foot is interpreted as the superimposition of a pure vibrational Q(1) branch and of broadened rotational structures connected to R( j0) and R( j1) ( j=0,1,2) signals. Moreover, there is not a dominant channel for the vibrational relaxation mechanism of CH3F trapped in argon matrix, since the transfers to the orientational modes, to the local or to the bulk phonon modes are shown to be equally efficient, with times (∼10 μs) in agreement with experimental data. In xenon matrix, the direct transfer to the lattice vibrations seems to be the most efficient mechanism of relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456076
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Vibrational relaxation of ND3 trapped in a rare gas matrix. A comparative study with NH3 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5650-5653 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The behavior of the vibrational relaxation time of ammonia molecule trapped in rare gas matrices with an isotopic substitution (ND3) is discussed within the framework of nonadiabatic coupling theory recently developed. The various factors which are subjected to changes in the H→D substitution are analyzed, and it is shown that the transfer of the vibrational energy to the orientational modes is here again the most efficient when compared to the multiphonon relaxation. The relaxation times are calculated to be 20 and 3 times longer for the deuterated species in argon and xenon matrices, respectively. When T is raised from 10 to 30 K, the vibrational relaxation efficiency is still enhanced in favor of NH3 since the efficiency rate factors become 40 (Ar) and 8 (Xe) smaller for ND3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455571
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Vibrational relaxation of ammonia trapped in rare gas matrices (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4559-4575 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory of the vibrational energy relaxation of a symmetric top molecule trapped in a rare gas matrix is presented. The direct relaxation mechanisms of the energy on the molecular orientation and on the lattice vibrations (including the local modes) are described within the framework of the nonadiabatic coupling between the internal vibrational mode of the molecule and the low-frequency external modes. The three types of relaxation constants are analyzed. The transfer to the orientational modes of the molecule is shown to be the more efficient since the corresponding relaxation time ranges between 1 μs and 50 ns, according to the nature of the rare gas matrix and to the temperature. The multiphonon relaxation constant is calculated for two specific deexcitation channels. The phonon multimode process provides relaxation times which range between 1 ms and 10 μs. Such a process is a characteristic of the nonadiabatic treatment of the total Hamiltonian. In contrast, the multiphonon monomode process, where the vibrational energy is transferred to the vibration of the center of mass of the molecule, gives larger relaxation times around 1 ms. This process is connected to the high orders in the interaction potential anharmonicity. The third species of relaxation constant which mix the orientational and translational processes is also analyzed for various typical relaxation channels. The corresponding relaxation times are one order of magnitude longer than those obtained from the multiphonon mechanisms. The calculated relaxation times are close to the experimental measurements and exhibit the same trends with rare gas changes and temperature rises.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452868
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    NH3 inversion in condensed media. Static, dynamic, and inhomogeneous environmental effects on the internal tunneling (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2172-2180 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ν2 umbrella mode of vibration–inversion of ammonia trapped in condensed media exhibits typical tunneling slow-down due to the statics, the dynamics, and the inhomogeneity of the ambiant solid. The reduction of the level splitting of the ν2 mode of ammonia from 37.6 cm−1 in gas to 24 cm−1 in argon, to 22 cm−1 in xenon, and to 1.65 cm−1 in nitrogen is interpreted in terms of the statical and dynamical influence of the matrix. In argon, the static environment accounts for 92% of the tunneling slow-down. In xenon, 45% of the effect is due to the dynamical inertia of the surrounding matrix. In nitrogen, the Franck–Condon dynamical influence represents about 70% of the effect. These results are in good agreement with experimental data and are consistent with results observed in other physical cases (phase transitions, superconductors, proton transfer). It is also shown that the environmental inhomogeneity due to the presence of other ammonia molecules cannot be neglected for the determination of the inversion level splitting in nitrogen matrix, even for high dilution (c≤1/20 000) of ammonia molecules in the solid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457025
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Dynamics of NH3 trapped in N2 matrix: Tunneling, motional narrowing, and vibrational relaxation (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1423-1433 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quantitative interpretation of the features observed in the high-resolution infrared profile and in the vibrational relaxation of the umbrella ν2 mode of ammonia trapped in a nitrogen matrix is given through the coupled dynamical study of the molecule and the crystal. The motional narrowing that occurs in the quadruplet structure of the vibration–inversion spectrum, as temperature rises, is due to the closing of the inversion levels of the two isotopic ammonia species (A2 and E) by dynamical coupling with the ambient solid. Indeed, this coupling is responsible for the tunneling slowdown of the ammonia frequency due to the tendency for the bath to localize the molecule in a given inversion state. The temperature behavior of the experimental profile in the range 5.5–25 K is well explained on the basis of inversion–libration relaxations assisted by one and two bulk phonon–libron processes. Moreover, the fast vibrational relaxation is also interpreted, within our approach, as being assisted by the ammonia orientational modes. The calculated relaxation time (0.05 ns) agrees with the experimental one (0.07 ≤τ≤ 2ns).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457102
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Generalized Langevin equation approach for the rotational relaxation of a molecule trapped in a 3D crystal. II. Application to CO and CH3F in argon (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4809-4822 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A numerical integration of the Langevin equations connected to the motions of a diatomic molecule trapped in a rare gas matrix is performed using a Runge–Kutta procedure and a Monte Carlo–Metropolis sampling for the initial configurations of the so-called primary system (cf. paper I). The rotational energy transfer from the molecule to the crystal is shown to strongly depend on the coupling between the molecule and the nearest-neighbor (NN) atoms and also on the ability for these NN atoms to dissipate their energy into the bath. Several cases are discussed according to the values of the viscous terms describing the damping of the molecule rotation and translation and of the NN atom vibrations. The prolate CH3F molecule trapped in an argon matrix seems to relax more quickly its rotational energy than the nearly isotropic CO molecule. Special trajectory calculations, when the molecule is rotationally excited or in thermal equilibrium, are considered in order to study the well jump and the librational motion of the CO molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452842
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Generalized Langevin equation approach for the rotational relaxation of a molecule trapped in a 3D crystal. I. Theoretical considerations (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4802-4808 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The stochastic classical trajectory method is developed for the interpretation of the orientational relaxation of a diatomic molecule trapped in a rare gas matrix. The primary system formed by the molecule and four neighboring atoms is described as a 2D effective dynamical system, while the bath formed by the remaining degrees of freedom has the spatial (3D) dimension. Special emphasis is devoted to the determination of the viscous terms (connected to the molecule rotation and translation and to the four atoms vibrations) which are responsible for the various channels of energy dissipation in the bath. A Monte Carlo numerical procedure is applied in paper II to the dynamics of CO and CH3F molecules trapped in an argon crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453695
    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...