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  • 1
    Electronic Resource
    Electronic Resource
    Ab initio dynamic dipole polarizabilities for O2, its photoabsorption spectrum in the Schumann–Runge region, and long-range interaction coefficients for its dimer (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9802-9810 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Perturbed states representing the response to an external electric field are obtained in the multireference averaged coupled pair functional formalism based on orbitals which are optimized in a perturbed multireference self-consistent field procedure. For each perturbing operator perturbed wave functions for several frequencies of the perturbing field are obtained simultaneously. From these sets of perturbed states reduced spectra are derived which represent effective oscillator strength distributions. The broad shape of the Schumann–Runge continuum leads to a poor description of the dynamic polarizability for frequencies approaching the first pole when only vertical transitions are considered. To account for this effect the absorption spectrum in the Schumann–Runge region is calculated and the polarizability is described up to the range of anomalous dispersion. The dynamic polarizabilities and the interaction coefficients are found to be in excellent agreement with experimental data where it is available. Significant differencies of up to 20% are observed between our anisotropic interaction coefficients and earlier estimates obtained from semiempirical anisotropic dipole oscillator strength distributions. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477680
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  • 2
    Electronic Resource
    Electronic Resource
    Response to "Comment on ‘Ab initio dynamic dipole polarizabilities for O2, its photoabsorption spectrum in the Schumann–Runge region, and long-range interaction coefficients for its dimer' " [J. Chem. Phys. 111, 11236 (1999)] (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 11238-11239 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The oscillator strengths of the discrete part of the Schumann–Runge band system is recalculated from single-state calculations using the adiabatic potential curve. Potential curves for three 3Πu states are computed. The integrated oscillator strength for the 3Πu←3Σu transition is recalculated from four-state coupled diabatic calculations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480482
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamic multipole polarizabilities, reduced spectra, and interaction coefficients for N2 and CO (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 9618-9624 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reliable ab initio reduced spectra that serve to calculate dynamic polarizabilities as well as long-range interaction coefficients are presented. The reduced spectra are constructed from perturbed functions that are computed in the single excitation multi-reference averaged coupled pair approach. The static dipole polarizabilities are of the same quality as values obtained in a recent study using elaborated coupled cluster expansions. The dynamic dipole polarizabilities are in excellent agreement with all experimental data available. The higher multipole polarizabilities (l≤3) are also expected to be the most reliable ones up to date. The interaction coefficients for the N2–N2 interaction perfectly match the coefficients obtained from semiempirical anisotropic oscillator strength distributions. For the CO–CO interaction, however, the same quantities differ by up to 10%. We believe our coefficients to be accurate to 3%. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480336
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  • 4
    Electronic Resource
    Electronic Resource
    Ab initio dynamic multipole polarizabilities and hyperpolarizabilities of H2O and the long-range interaction coefficients for its dimer (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1532-1543 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Perturbed states representing the response to an external electric field are obtained from multi-reference configuration interaction wavefunctions. The multi-configurational reference function is designed to represent the ground state as well as the perturbed and even the first excited states on equal footing, i.e., orbital optimization is performed in a perturbed multi-reference self-consistent field procedure. For various perturbing operators, several perturbed wavefunctions for different frequencies of the perturbing field are obtained simultaneously with the corresponding lowest excited state. From these sets of perturbed and excited states, reduced spectra are derived which represent effective oscillator strength distributions and serve to calculate dynamic polarizabilities, hyperpolarizabilities, and long-range interaction coefficients. The results for both the dynamic polarizabilities and the interaction coefficients are found to be in excellent agreement with experimental data and other accurate theoretical values. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475551
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  • 5
    Electronic Resource
    Electronic Resource
    A variational method for the calculation of rovibrational energy levels of triatomic molecules using a Hamiltonian in hyperspherical coordinates: Applications to H+3 and Na+3 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 2104-2117 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A full variational procedure is presented for the calculation of rovibrational (J(approximately-greater-than)0) energy levels which is particularly suited for triatomic potentials that support large amplitude motions and that may be of high permutational symmetry. It is based on a kinetic energy operator expressed in hyperspherical coordinates (ρ,aitch-theta,Φ). Particular attention is paid to the singularities of this operator in the derivation of the primitive basis functions, which should exactly cancel all singularities, and in their subsequent contractions. The method is applied to the D3h molecules H+3 and Na+3, for which converged rovibrational energies are calculated for J=0, 1, 2 to 25 000 cm−1 for H+3 and to 1250 cm−1 for Na+3, respectively. A spectral analysis of these energy levels is undertaken. For the lowest ten vibrational levels of H+3, converged rovibrational energies up to J=10 are also calculated. These energies, which extend previous calculations, should prove useful in the interpretation of the observed spectra. Our J=1 results for H+3 compare well with recently published values. The results for Na+3 constitute new data which supplement our previous J=0 calculations. It is shown that the spectrum of this molecule can be expressed very well by an appropriate effective Hamiltonian, quite in contrast to H+3. In order to verify that the method is general, J(approximately-greater-than)0 calculations are performed for model potentials of H2O+ (C2v) and HLiH− (D∞h). The results are in full agreement with those from a proven variational method in valence coordinates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466507
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  • 6
    Electronic Resource
    Electronic Resource
    Static dipole polarizabilities of Li2, Na2, and K2 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 953-957 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Static dipole polarizability functions (α(parallel) and α⊥) and thermally averaged isotropic polarizabilities (α) of Li2, Na2, and K2 in their electronic ground states have been obtained from all-electron SCF+valence CI calculations which include core polarization effects by use of an effective potential. As a function of internuclear separation, α⊥ shows a monotonic increase in all three cases while α(parallel) exhibits a pronounced maximum at about 1.5 Re. For T=300 K, we find α(Li2)=214, α(Na2)=262, and α(K2)=477 a.u. Our results, to which we attribute an uncertainty of 2%, support the measured value for the average polarizability of Li2 [R. W. Molof et al., J. Chem. Phys. 61, 1816 (1974)] but disagree with their results for Na2 and K2. For these dimers, Molof 's mean experimental values appear to be in error by 33% and 18%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451251
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  • 7
    Electronic Resource
    Electronic Resource
    Ab initio calculation of near-equilibrium potential and multipole moment surfaces and vibrational frequencies of H+3 and its isotopomers (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 891-900 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: H+3 potential energies and multipole moments are calculated from a full CI with a 10s, 4p, 2d GTO hydrogen basis. 69 calculated energy points with energies of up to 25 000 cm−1 above the minimum are fitted by a power series expansion in terms of a Morse-type coordinate with a mean square error of less than 1 cm−1. Rotationless vibrational states with energies of up to 12 000 cm−1 above equilibrium are calculated variationally for ten isotopomers. The resulting band origins for the seven analyzed fundamental transitions show a mean deviation of less than 2 cm−1. For the other predicted frequencies, the errors are expected to be below 0.1% also. The equilibrium bond length of H+3 is predicted to be 0.8732(2) A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450534
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  • 8
    Electronic Resource
    Electronic Resource
    Dipole-allowed excited states of N2: Potential energy curves, vibrational analysis, and absorption intensities (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 6438-6449 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The three lowest adiabatic potential energy curves for each of the two dipole-allowed symmetries, 1Σu+ and 1Πu, are calculated in the multireference configuration–interaction framework. Diabatic potentials and corresponding coupling elements are obtained by diagonalizing the electronic operator r2 which serves to discriminate Rydberg and valence type states. A large basis set and judiciously chosen active orbital and configuration spaces furnish smooth and reliable potential curves. However, a vibrational analysis of the coupled systems in diabatic representation still shows some disappointing deviations from the experimental interference patterns of overlapping absorption bands that are highly sensitive to potential energy differences. Starting from the calculated curves, a fitting procedure accounting also for empirical information yields potential energy curves and diabatic coupling elements that reproduce all details of the experiment very well. These recommended results also serve to identify residual defects in the ab initio curves mainly as vertical shifts. The performance of other commonly used ab initio methods for the calculation of excited states is briefly discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1400139
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamic multipole polarizabilities and long range interaction coefficients for the systems H, Li, Na, K, He, H−, H2, Li2, Na2, and K2 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7845-7858 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Different approaches to the calculation of dynamic polarizabilities are briefly discussed and compared. Using a perturbational approach dynamic multipole polarizabilities are calculated from full valence configuration interaction wave functions. The polarizabilities are expressed in terms of reduced spectra which, in turn, are used to compute the dispersion and induction coefficients for all combinations of the systems listed, including anisotropic contributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465663
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  • 10
    Electronic Resource
    Electronic Resource
    Long-range interaction coefficients for the metastable states of He (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8351-8352 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Following the lines presented in a recent paper [J. Chem. Phys. (unpublished)] reduced spectra representing the dynamic polarizabilities are reported with special emphasis on accurate values for the metastable states of the He atom. Together with the reduced spectra taken from Ref. 1, long range interaction coefficients are computed for all combinations between the three lowest He states and the atoms H, Li, Na, K, and H−.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465610
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