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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 504-512 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio methods were applied to compute the potential curves for the X 3Σ− and A 3Π states, the transition dipole moment, and the radiative lifetimes of the vibrational levels of the A state of the SO molecule. Extended atomic natural orbital basis sets including up to g-type functions were used. The potential energy curves were computed at the multireference configuration interaction level of approximation. The calculated bond distances and bond energies are 1.498 (1.481) A(ring) and 5.21 (5.36) eV, respectively, for the X state, and 1.694 (1.609) A(ring) and 0.57 (0.64) eV, respectively, for the A state (experimental values within parentheses). Restricted active space self-consistent field (RASSCF) wave functions were used to obtain the transition dipole moments, and the size of the RASSCF active orbital space was increased until stability of the transition moment value was achieved. The calculated transition moment strongly depends on the internuclear distance. The calculated value of the A 3Π, v=0 lifetime is 46.6 μs, while the experimental values are in the range of 36–39 μs. The computed lifetime is a very sensitive function of the relative accuracy of the potential energy and transition moment curves: for example, removing the g-type function on sulphur increases the lifetime to 55 μs.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 44 (1977), S. 109-127 
    ISSN: 1432-2234
    Keywords: Electric moments ; Polarizability ; Susceptibility ; Nuclear magnetic shielding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A comprehensive analysis of the reliability of computed first- and second-order properties is attempted. The best and most recent experimental and theoretical data available in the literature have been compiled and compared to those obtained using moderately sized and extensive basis sets in calculations at the coupled Hartree-Fock level. It is concluded that prediction of the properties dealt with in this paper is, in general, safe though there are certain problems concerning the description of charge density polarization phenomena.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 100 (1998), S. 65-77 
    ISSN: 1432-2234
    Keywords: Key words: Dissociative recombination ; HeH Rydberg states ; Adiabatic corrections ; Diabatic coupling ; Radiative ; and non-radiative reaction rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. The repulsive ground electronic state X2Σ+ of HeH is strongly coupled to the Rydberg states at small interatomic distances. Such large couplings also occur between some of the Rydberg states. HeH+ ions that capture an electron in a Rydberg state end up in separated He and H atoms by indirect predissociation. This paper presents a study of potential functions and pertinent matrix elements involving the lowest electronic states: the 2Σ+ states, X, A, C, and D, and the 2Π states B and E. Individual transition rates as well as total radiative and non-radiative lifetimes have been computed for the lowest vibrational and rotational levels.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 23 (1972), S. 393-397 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The energy of the dihydrated lithium cation Li+·2H2O is studied in several different points within the SCF MO LCAO framework, using a gaussian basis set to approximate the wavefunction. The computed binding energies (hydration energies) and bond distances are compared to the values found for the monohydrate. The results are discussed in view of ion-solvent interaction, and especially of the effect of ions on adjacent hydrogen bonds, in aqueous solutions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 23 (1972), S. 387-392 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The energy surfaces of the systems LiOH 2 + and NaOH 2 + are studied for a number of different geometries within the SCF MO LCAO framework, using a gaussian basis set to approximate the wavefunction. In the minimum energy geometry of both systems the positive ion is bound to the oxygen atom of the water molecule. The computed binding energies and bond distances are: B SCF(LiOH 2 + ) = 36.0 kcal/mole, d(LiO) = 3.57 a.u., and B SCF(NaOH 2 + ) = 25.2 kcal/mole, d(NaO) = 4.23 a.u., resp. The results are compared with those of H3O+ and discussed in view of ion-solvent interaction in aquous solutions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 27 (1972), S. 265-272 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The energy surface of the dihydrated fluoride anion (F·2H2O)−1 is studied for a number of different geometry points near the equilibrium structure within the SCF LCAO MO framework, using an extended gaussian basis set to approximate the molecular wavefunctions. For the first and second hydration step of the fluoride anion the corresponding hydration energies are calculated to beB 1 scf =24.1 kcal/mole andB 2 SCF =20.8 kcal/mole (experimental measurements: 23.3 kcal/mole and 16.6 kcal/mole, respectively). The hydration energies and equilibrium bond distances obtained for the dihydrated fluoride anion (F·2H2O)− are compared with those found for the monohydrate (FHOH)− and with corresponding results of the dihydrated lithium cation (Li · 2H2O)+. The system (F·2H2O)− is taken as a very simple model to discuss some basic features of the hydration process of small ions and to study the influence of a negative ion on an adjacent hydrogen bond.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 36 (1975), S. 249-274 
    ISSN: 1432-2234
    Keywords: Configuration interaction ; Hydrogen bonding ; Ion hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previous single-determinant Hartree-Fock studies on the equilibrium structures and stabilities of H2 O, H3 O+ as well as of the monohydrated ionic systems Li+ · H2O, F− · H2O and the hydrogen bonded water dimer, H2 O · HOH, are extended by large scale configuration interaction calculations including all the possible single and double excitations arising from the canonical set of Hartree-Fock molecular orbitals. The correlation energy effects on the equilibrium geometrical parameters of the systems under consideration are found to be quite small. The contributions of the correlation energy to the total binding energies of the weakly interacting composed systems are obtained to be of the order of 1 kcal/mole, leading to a considerable increase of the hydrogen bond strength in F− · H2O and H2O · HOH and to a small decrease of the binding energy in Li+ · H2 O. The observed strengthening of the hydrogen bonding interaction due to correlation is shown to be partly compensated by the change in the vibrational zero-point energy of the composed systems compared to the non-interacting subsystems. Approximate force constants corresponding to the intersystem vibrations in Li+ · H2O, F− · H2 O, and H2O · HOH are deduced from the calculated potential curve data on the SCF and the CI level of accuracy.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 42 (1976), S. 77-82 
    ISSN: 1432-2234
    Keywords: Configuration interaction ; Hydrogen bonding ; Ion hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Large-scale configuration interaction (CI) calculations have been performed in order to study the effect of the correlation energy on the equilibrium geometrical structure, the stability, and on the energy barrier of the proton transfer reaction in the hydrogen bonded system HO− · HOH. An extended Gaussian basis set including polarization functions on each nuclear centre has been employed to approximate the molecular Orbitals. All possible single and double replacements resulting from a single determinant Hartree-Fock reference state have been taken into account in the CI wavefunction. Compared to the SCF results the equilibrium oxygen/oxygen distance has been obtained from the CI calculations to be smaller by about 0.08 Å and the correlation energy has been found to stabilize the composed system by 3.6 kcal/mole. An almost symmetric equilibrium structure with the hydrogen bonding H-atom midway between the two oxygen centres has been obtained in the CI treatment, whereas SCF calculations yield an asymmetric geometrical configuration with a small energy barrier of 1.4 kcal/mole for the proton transfer process.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 23 (1972), S. 398-403 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The closed shell ground state of the system (HOHOH)− has been studied for different geometrical configurations within the SCF LCGO MO framework, using an extended basis set of gaussian type functions to approximate the molecular wavefunctions. The most stable structure was found to have a linear, slightly asymmetrical hydrogen bridge between the two oxygen nuclei. The OO-distance was determined to be d(OO)=4.75 a.u. (=2.51 Å), and a binding energy, relative to the subsystems H2O and OH−, of B=24.3 kcal/mole was obtained, in reasonable agreement with the most recent experimental measurement (B exp = 22.5 kcal/mole). The proton transfer process between the two subsystems has been studied in a range near the equilibrium OO-distance.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 28 (1972), S. 67-74 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Energiehyperflächen des NH3 · H2O-Systems wurden für eine Anzahl von verschiedenen geometrischen Anordnungen untersucht. Im Falle der Struktur minimaler Energie wird eine lineare Wasserstoffbindung gebildet, NH3 wirkt als Protonakzeptor. Die Berechnungen ergeben eine Bindungsenergie des Systems von 6,28 kcal/Mol und einen NO-Abstand von 3,07 Å. Außerdem wurde die Potentialkurve für die Inversion des über eine Wasserstoffbrücke gebundenen NH3 berechnet und diskutiert.
    Notes: Abstract The energy hypersurface of the system NH3 · H2O is investigated for a number of different internuclear geometries. In the minimum energy structure involving a linear hydrogen bond, NH3 acts as proton acceptor. The binding energy of the system is calculated to be 6.28 kcal/mole and the bond distance d(NO) to be 3.07 Å. The potential energy curve of the inversion of the hydrogenbonded NH3 is computed and discussed.
    Type of Medium: Electronic Resource
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