摘要:

The branch point structure of a group of eigenvalues that are functions of some parameter is used to derive a method for their analytic continuation as the solutions of an algebraic equation. The procedure is valid so long as no member of the group branches with the rest of the spectrum. The perturbation series for the total projection operator for the group is derived in a form such that small denominators due to near degeneracy are eliminated. This then allows the continuation of eigenfunctions and properties by diagonalization of the projected hamiltonian. This provides a formalism for nearly degenerate perturbation theory with clear convergence properties. Other treatments may be obtained by suitable choice of a transformation function that relates the group projector to its unperturbed value; it is shown that the function proposed by Kato has useful diabatic properties.

ISSN:0026-8976    

DOI:10.1080/00268977800102091

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The infra-red and Raman spectra of normal and heavy water have been calculated, within the framework of the fluctuation hypothesis of hydrogen bonding, in good agreement with experiment. The necessary set of initial parameters estimated from the spectra of HOD and water vapour appears to be practically the same for H2O and D2O as well as for the spectra of infra-red absorption and both Raman polarizations. The frequencies and intensities of eigenvibrations for all types of spectra have been calculated using the method of partial oscillators, using 100 000–1 000 000 H2O (D2O) molecules variously perturbed by local environmental fluctuations. The calculation carried out is the first complete synthesis of spectral contours for water and gives their physical interpretation. It is shown that the main factor which determines the spectral shape for H2O and D2O together with its temperature variation is the intramolecular coupling of stretching vibrations of OH groups and the overtone of bending vibration (Fermi resonance). It is not necessary to postulate the existence of discrete species of aggregates nor the displacement of the equilibrium between them in the liquid. The band structure found reveals the inadequacy of the widespread method of interpretation of contour shapes by their computer decomposition into various components.

ISSN:0026-8976    

DOI:10.1080/00268977800102101

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Absorptions from the triplet exciton bands in benzophenone, benzil and benzoin have been observed in crystals excited by 337 nm light from a N2laser. In benzophenone and benzil, the crystal absorptions are much wider than those of the isolated molecules, showing that considerable mixing between the upper triplet exciton states and singlet and CT states is taking place. The phosphorescence spectrum of benzophenone crystals at high density excitation shows a (0, 0) band which is much weaker relative to the (0, 1) band than at low density excitation : this has been attributed to a high concentration of phonons in the crystal. The high excitation density also enabled the triplet-triplet exciton annihilation rates for benzophenone to be measured :γTT(295 K) = 1 × 10-18m3s-1andγTT(77 K) = 6 × 10-9m3s-1.

ISSN:0026-8976    

DOI:10.1080/00268977800102111

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268977800102121

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The quantum-mechanical calculation of the molecular force field in rectilinear and curvilinear internal coordinate representation is discussed. A method to calculate curvilinear displacements is outlined. A formula is given to transfer the rectilinear cubic force field between isotopically related molecules. The quadratic CNDO/2 force field for CHF3is presented in curvilinear and rectilinear coordinate representation in order to illustrate the influence of isotopic substitution and coordinate stepsize.

ISSN:0026-8976    

DOI:10.1080/00268977800102131

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The nuclear magnetic shielding of29Si,31P,33S and35Cl in SiH4, PH3, SH2and ClH has been computed. The inner shells of the heavy atom are not introduced in the calculation for the molecule. Their effect on the valence shell is represented by a pseudo-potential. The agreement with available theoretical and experimental values is satisfactory.

ISSN:0026-8976    

DOI:10.1080/00268977800102141

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

L'étude par corrélation angulaire γ-γ perturbée du tropolonate de hafnium Hf(C7H5O2)4—noté Hf(T)4—montre que le couplage quadrupolaire au niveau du métal est fortement influencé par la complexation à l'état solide de ce chelate avec des molécules organiques polaires, telles que le chloroforme ou la N,N-diméthylformamide (DMF). La variation de la fréquence quadrupolaire avec la température peut ˆetre interprˆetée à l'aide du modèle de Bayer-Kushida. Dans le cas du système Hf(T)4-DMF, cette fréquence présente une variation non monotone entre 20 K et 390 K. Une interprétation de cette variation, cohérente avec les données de diffraction de rayons X et de spectroscopie infra-rouge, consiste à faire intervenir dans le modèle deux modes de vibrations. Le premier a une fréquence constante, de 63 cm-1. Le second, de type ‘soft mode’, est responsable d'une transition àTc= 145 K et sa fréquence varie comme (T - Tc)1/2. Cette transition se traduit essentiellement par un changement de configuration de la molécule de DMF qui semble favoriser, dans la phase à haute température, l'interaction de cette molécule avec les électrons π du cycle de l'un des deux ligandes tropolonate voisins.

ISSN:0026-8976    

DOI:10.1080/00268977800102151

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The high-resolution electronic bands of theÃ1A′-[Xtilde]1A′ absorption system of 2-chloro- and 1-chloronaphthalene have been analysed by the method of rotational band contours. The excited state rotational constants of 2-chloronaphthalene may be interpreted in terms of a planar geometry of the molecule in the excited state, but no such explanation seems possible for 1-chloronaphthalene. It is found that the perturbing effect of chlorine substitution on the 312 nm electronic transition of naphthalene is significantly different from that of F, OH and NH2.

ISSN:0026-8976    

DOI:10.1080/00268977800102161

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A rigorous diagrammatic analysis of the origin of the RISM equation is presented. Some properties of the RISM equation are deduced.

ISSN:0026-8976    

DOI:10.1080/00268977800102171

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A two-dimensional model of a Jahn-Teller system with strong first and weak second-order vibronic coupling is analysed. Separation of the variablesrand φ is achieved in the adiabatic approximation for the angular motion.

ISSN:0026-8976    

DOI:10.1080/00268977800102181

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor