摘要:

A parameterization scheme for the electric dipole intensities of one-phonon vibronic (f-f) transitions in rare-earth (lanthanideandactinide) complexes is proposed. This parameterization is perfectly general within the one-electron, one-phonon, one-photon approximation for ion-ligand-radiation field interactions, and it is directly related to a general intensity parameterization scheme proposed previously for purely electronic (zero-phonon)f-ftransitions. The parameters in this scheme can provide a basis for characterizing one-phonon vibronic line intensities inf-foptical spectra without recourse to specific model (or mechanism)-dependent considera tions. Applications of this parameterization to the vibronic spectra of octahedral (Oh) REL6systems are discussed, and it is shown how the intensity parameters for these systems may be expressed in terms of a set of ‘intrinsic’ intensity parameters (in the superposition approximation for RE-L interactions). Finally, the parameterization scheme is applied to thev3(t1u) vibronic line intensities reported in the literature for the UCl62-complex.

ISSN:0026-8976    

DOI:10.1080/00268978400100691

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The two-photon transition probability per unit photon flux has been calculated for the process in which two photons, of generally different frequencies, induce the excitation from the ground states of neon and argon to some of the low-lying excited states. The matrix elements, needed to perform the summation over the intermediate states, were obtained by exploiting the results of a random phase approximation calculation. Both the length and velocity form of the perturbation operator were employed and the discrepancies between the corresponding results are discussed. The calculations refer to the experimental set-up in which two linearly polarized photons with parallel polarization vectors are used.

ISSN:0026-8976    

DOI:10.1080/00268978400100701

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Ab initioMRD-CI calculations are reported for the potential curves of ground and excited states of the SiP+molecular ion employing a large DZP AO basis. Secular equations of up to order 12 000 have been solved thereby and polarization functions of bothd- andf-type have been included in the theoretical treatment. The ground state of this as yet unobserved system is found to be3Σ-, in contrast to isovalent first row species such as CN+and C2, which possess1Σ+ground and very low-lying3Π excited states. The ordering of states in SiP+is similar to that of Si2, but the energy separation between theX3Σ-andA3Π states is larger in the heteronuclear molecule. Spectroscopic parameters are also computed, including Franck-Condon factors and transition probabilities for various dipole-allowed excitations, in order to aid in the future experimental identification of this system. Finally a comparison of the electronic structure and properties of SiP+is made with those of a series of isovalent systems for which calculation are available at the same level of theoretical treatment and the trends found thereby are analysed and discussed.

ISSN:0026-8976    

DOI:10.1080/00268978400100711

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Three-body energies have been calculated for clusters of Li+and F-ions at the geometries of the nearest neighbour clusters in a LiF crystal. For three ions of the same type, the three-body energy is given accurately by the classical expression for the non-additive part of the induction energy. For clusters containing both cations and anions, three-body energies are larger and charge transfer is found to be more important than induction.

ISSN:0026-8976    

DOI:10.1080/00268978400100721

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The dielectric permittivity of a model fluid representing methyl cyanide has been studied with a view to testing a recently developed theory of the frequency dependent dielectric permittivity. Although there are large correlations between the orientations of dipoles the Kirkwoodgfactor is close to the trivial value of unity; this contrasts with the behaviour of Stockmayer and similar model fluids and is a consequence of the molecular shape. The time dependence of both the longitudinal and transverse components of the dipole density is obtained and related to the relaxation of the single molecule dipole correlation function. The applicability of the ‘dipolaron’ description to the oscillation observed in the relaxation of the longitudinal component is examined.

ISSN:0026-8976    

DOI:10.1080/00268978400100731

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A theoretical decomposition of the dielectric spectrum of a fluid with permanent and interaction-induced dipoles is discussed. The spectrum is separated into a term which has the ‘re-orientational’ frequency dependence of the permanent dipole density, modified by a ‘local field factor’ and a ‘collision-induced’ term. The utility of this decomposition in representing the frequency dependent permittivity of a computer simulation of methyl cyanide is considered. Both permanent dipoles and the dipoles induced by the fields from the permanent charge distributions of other molecules are considered and the calculated permittivity is in good agreement with that obtained in experimental studies. The value of the local field factor is compared with the value predicted by a theory which leads to the Fröhlich expression for the static permittivity.

ISSN:0026-8976    

DOI:10.1080/00268978400100741

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A new conformal solution theory using a single pure fluid as a reference substance for the calculation of thermodynamic properties of fluid mixtures is developed. The perturbation theory developed by Weeks, Chandler and Andersen (WCA) and by Verlet and Weis (VW) is used to calculate the reference properties. The mean density approximation and corresponding state principle are used to eliminate the higher order terms in the mixture system and to derive the pseudo-parameters for the reference system. The mixture properties are obtained from the reference properties and their corresponding hard sphere excess functions defined as the properties of the mixture less the value of the properties for the hard sphere mixture.

ISSN:0026-8976    

DOI:10.1080/00268978400100751

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

5-Hydro-6-methyl-6-yl-uracil (HMU) radicals generated from 5,6-dihydro-6-methyluracil or 6-methyluracil by X-irradication have been studied in single crystals, polycrystalline powders and aqueous glasses of both compounds. In all matrices the spectra of the HMU radicals show a strong temperature dependence attributable to thealternating linewidth effect. By simulation of the spectra exchange rates have been determined for the methylene protons at C5. It is shown that structure and conformation of the HMU radical are essentially independent of the precursor molecule and of the matrix. The differences observed in the temperature dependence of the spectra can be explained completely by thermal motions of the radicals, which are differently impeded by the different molecular packings of the respective matrices.

ISSN:0026-8976    

DOI:10.1080/00268978400100761

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Linear and non-linear light scattering in static magnetic fields by molecules with orbitally degenerate ground states is investigated. The temperature dependent circular intensity difference (CID) spectrum induced by the orientational mechanism is calculated by taking into account the rotational diffusion.

ISSN:0026-8976    

DOI:10.1080/00268978400100771

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The reaction path hamiltonian of Miller, Handy and Adams was used to investigate the isomerization CH3O → CH2OH, which is of interest in atmospheric chemistry. The equilibrium configurations, transition state and reaction path were calculated using the restricted Hartree-Fock (RHF) and complete active space self consistent field (CASSCF) methods, with STO-3G and double zeta basis sets.

ISSN:0026-8976    

DOI:10.1080/00268978400100781

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor