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  • American Institute of Physics (AIP)  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Extended measurements of the ν2 band of CD3 and the determination of the vibrational potential function for methyl (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2125-2133 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements in the ν2 (umbrella) vibrational spectrum of CD3 are reported. The data include transitions up to and including the v2=4–3 bands and cover a wider range of rotational excitation than has been previously reported [Frye, Sears, and Leitner, J. Chem. Phys. 88, 5300 (1988)]. The spectroscopic data have been combined with all previously published data pertaining to the methyl radical and an estimate of the vibrational potential function for the species has been made. From this, we predict the positions of so far unobserved vibrational bands for all the various symmetric isotopic modifications and also extract an equilibrium structure. Preliminary results on the population distribution of v2 levels produced on the photofragmentation of acetone-d6 at 193 nm are reported and it is suggested that the methyl v3=1 and v3=0 levels may be produced in this reaction with a population inversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456006
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  • 2
    Electronic Resource
    Electronic Resource
    Nonadiabatic corrections for coupled Morse oscillators using Hutson and Howard perturbation theory (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8916-8921 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An adiabatic separation is applied to two coupled Morse oscillators. The resulting approximate energies and wavefunctions are corrected for nonadiabatic interactions by means of the perturbation theory approach of Hutson and Howard supplemented by the "Padé divergent series summation'' technique. The convergence properties of the perturbation series are investigated as functions of the oscillator frequencies and coupling strengths varying over a wide range of values. The rate of convergency and accuracy of summability of the perturbation series depend strongly on the presence of accidental resonances among the adiabatic levels. For relatively well isolated levels, the series either converge strongly or can be summed very accurately for almost any strength of perturbation. In the case of close coincidence of more than two strongly coupled levels, the approach becomes unreliable. The convergency/summability problems faced in the "intermediate'' cases of two "adiabatically crossing'' levels appear to be curable by means of interpolating over the "near-degeneracy'' regions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468945
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular quadrupole moment function of ammonia (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 11068-11074 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The zz component of the molecular quadrupole moment aitch-theta of ammonia is computed at the restricted Hartree–Fock and coupled cluster theory with singles and doubles (CCSD) levels of approximation as a function of the symmetric stretching and inversion motions, considering a wide range of values for the corresponding vibrational coordinates (z is the threefold symmetry axis). Using these results and the nonrigid invertor rovibrational wave functions, effective molecular quadrupole moments are obtained for the low lying roinversional states of 14NH3. The predicted values exhibit a sizable and nonmonotonic dependence on the corresponding inversional (v2) and rotational (J,k) quantum numbers. The calculated effective quadrupole moments for the vibrational (inversional) ground states (v2=0±) are found to be about 10% smaller in absolute value than the two available experimental results [−2.42±0.04 a.u.; J. G. C. M. van Duijneveldt-van de Rijdt and F. B. van Duijneveldt, J. Mol. Struct. (THEOCHEM) 89, 185 (1982) and −2.45±0.3 a.u.; S. G. Kukolich, Chem. Phys. Lett. 5, 401 (1970); 12, 216 (1971) (E)]. Our CCSD value of the quadrupole moment pertaining to the equilibrium geometry is in a very close agreement with the best theoretical values that are available in the literature. This fact and the high quality of the roinversional wave functions that were employed lead us to believe that our theoretical predictions may be more accurate than their experimental counterparts. In particular, the difference between the theoretical and experimental values casts doubt on the reliability of the error bars (±0.04 a.u.) in one of the experimental results quoted above. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472907
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  • 4
    Electronic Resource
    Electronic Resource
    Bound and quasibound states of the Na(centered ellipsis)FH van der Waals molecule (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 189-202 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A recently developed diabatic representation for the two lowest 2A′ electronic states of the NaFH system [M.S. Topaler, D.G. Truhlar, X.Y. Chang, P. Piecuch, and J.C. Polanyi, J. Chem. Phys. 108, 5349 (1998)], augmented with highly accurate multireference configuration interaction data, is used to construct a new potential energy function for the ground electronic state of NaFH. The refined potential is used to calculate the bound and quasibound rovibrational states of the Na(centered ellipsis)FH molecule. The focus is on the quasibound states corresponding to excitation of the H–F mode in the complex, although states in which the H–F mode is not excited are also studied. All rovibrational calculations are performed within the framework of the Sutcliffe–Tennyson Hamiltonian for triatomic molecules. The energy positions and lifetimes of quasibound states are obtained using the stabilization method. Three methods are employed to solve the rovibrational problem: (i) the variational approach, in which the Hamiltonian matrix, as defined by a discrete basis set, is diagonalized, (ii) the coupled-channel method, in which the van der Waals stretching coordinate is handled by direct numerical propagation on a grid, and (iii) two perturbative approaches based on the adiabatic separation of vibrational motions. The effect of rotational excitation on the lifetimes of calculated resonances is studied. The main results of this study are the strong evidence for the existence of many long-lived rovibrational resonances corresponding to excitation of the H–F mode in the complex and the rationalization of this finding in terms of effective potentials defining adiabatic separations. Possible impact of the results obtained in this study on new experimental ways of probing potential energy surfaces of the NaFH system, with emphasis on the dynamics of photo-induced charge transfer in Na(centered ellipsis)FH, is discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480632
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  • 5
    Electronic Resource
    Electronic Resource
    Diode laser absorption spectroscopy of D3O+: Determination of the equilibrium structure and potential function of the oxonium ion (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 2676-2685 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution measurements of the two components of the ν2 (umbrella) fundamental mode of the fully deuterated oxonium ion (D3O+) are reported. The spectra were obtained by diode laser absorption in a plasma containing D2 and D2O. Analysis of the observed spectra yields precise estimates of the two band origins and molecular parameters describing the states involved. By combining these data with the available high resolution data for H3O+, using the nonrigid invertor Hamiltonian, we are able to determine the equilibrium structure and the vibrational potential function; also we predict the inversion spectrum of D3O+ and the 2v2–v2 hot band spectra of H3O+ and D3O+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449270
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