摘要:

A theory of vibrational relaxation in liquids is presented in which the vibrations are loosely coupled to a bath or lattice of molecular translations and rotations by intermolecular forces. Using the second-order perturbation expressions familiar from magnetic resonance the secular contribution to the line width is calculated. Different coupling paths are considered and expressions given for the line widths in a liquid mixture in terms of number densities and diffusion coefficients valid when reorientation is slow and translation diffusional.

ISSN:0026-8976    

DOI:10.1080/00268977700100831

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Simple MO theory is used to calculate the zero-field splitting parameterDof the lowest triplet state of double and triple-layered cyclophanes. Our approach explains the differences in theDvalues of diastereomeric intramolecular charge-transfer systems and the differences between phanes with identical aromatic units and those consisting of a donor and an acceptor.

ISSN:0026-8976    

DOI:10.1080/00268977700100841

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Electro-optical experiments on π-type molecular complexes are reported. Excited-state electric dipole moments are obtained and it is found that they decrease gradually in a series of complexes with a common acceptor (donor) as the donor (acceptor) becomes stronger. The magnitude of the excited-state dipole moments suggests a specific modification of the charge-transfer model for these complexes.

ISSN:0026-8976    

DOI:10.1080/00268977700100851

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The potential energy surface in the non-reactive region has been determined theoretically for the H2-H2system. The procedure consists of a non-orthogonal configuration interaction calculation using the individual SCF orbitals of the separate molecules. The potential function is expressed as a 5-term sum of Legendre functions, and analytical expressions are given for theRdependence of the terms. The calculated depth of the spherically averaged Van der Waals well is -2·96 meV, which is in essentially complete agreement with the experimental value of -3·00 meV. the position of the minimum is at 3·49 Å both theoretically and experimentally. The value ofC6for dispersion forces obtained in this calculation is 12·97 a.u.

ISSN:0026-8976    

DOI:10.1080/00268977700100861

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

In this paper we explore the feasibility of widening the scope of the non-perturbative open-shell many-body formalism recently developed by us [1], which utilizes an Ursell type of cluster expansion about certain starting wavefunctions spanning a model space. We show that, by generalizing the definition of the cluster expansion operator, we can incorporate into the model space (a) determinants differing widely in energy and (b) determinants differing in their number of electrons. This flexibility is useful for the calculation of difference energies of interest, like transition energies and ionization potentials of atomic and molecular systems. The generalized scheme has been tested on the 4π-electron problem trans-butadiene for which, by choosing a very general model space, we have calculated the energies of the ground, the lowest π-π* singlet and triplet and the first ionization potential by choosing a single composite cluster expansion operator for all states. Results for some more restricted choice of model spaces are also given. The agreement between the results of the present theory and that found from CI calculations, complete in the chosen basis, is excellent.

ISSN:0026-8976    

DOI:10.1080/00268977700100871

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The exchange dispersion energy for the interaction of two helium atoms is expressed as a sum of multipole components. In contrast to the analogous expansion for the dispersion energy the derived series converges very slowly and the rate of convergence does not improve with an increasing interatomic distance. Numerical calculations show that at the van der Waals minimum the first term of the series, referred to as dipole-dipole exchange energy, represents merely 17 per cent of the exchange dispersion energy. Moreover, even the inclusion of dipole-quadrupole and quadrupole-quadrupole terms can account for only half of the total exchange dispersion interaction. The above difficulty can be avoided by expanding the dispersion pair function in terms of ionic type or explicitly correlated functions.

ISSN:0026-8976    

DOI:10.1080/00268977700100881

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A non-product integration algorithm is used to compute the second virial coefficient of a number of potential functions proposed for nitrogen. It is shown that corrections to the orientational variation of the dispersion interaction assumed by a diatomic Lennard-Jones potential have a larger effect upon the second virial coefficient than does the inclusion of the electrostatic quadrupole interaction. We derive a nitrogen pair potential which should be useful for future research. This pair potential takes the form of an atomatom potential but unlike the diatomic Lennard-Jones potential has non-spherical inter-atomic interactions which combine to produce the known asymptotic form of the long-range interaction of two nitrogen molecules.

ISSN:0026-8976    

DOI:10.1080/00268977700100891

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

We extend earlier work of ours on the use of Padé approximants in the theory of multipolar and ionic potentials. The new features are (i) extension of our work to mixed multipole terms and inclusion of polarizability, (ii) formulation and implementation of a systematic means of getting analytic approximations for all the two-body and three-body terms appearing in the theory, (iii) assessment of the ionic Padé results in the low-concentration region important in ionic-solution applications, (iv) use of the Padé in a mixed perturbation theory of improved accuracy in that low-concentration regime. The results of (iii) and (iv) are used to study the remarkable lowdensity charged-sphere critical point recently discovered by Stell, Wu, and Larsen.

ISSN:0026-8976    

DOI:10.1080/00268977700100901

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The absolute Raman intensities and depolarization ratios of CHCl3and CDCl3have been measured in the gas phase. These magnitudes, the Raman tensors (including signs), as well as the electro-optical parameters of the C-H and C-Cl bonds have been calculated within the frame of the bond-polarizability theory. Several approximations of the theory are reviewed. The influence of the vibrational force field upon the electro-optical parameters is also checked.

ISSN:0026-8976    

DOI:10.1080/00268977700100911

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The convergence properties of long-range interactions in a periodic polar system are considered and an efficient method for their evaluation proposed. This method is applied to a Monte-Carlo simulation of water at 1 g cm-3and a nominal temperature of 300 K, using the ST2 potential of Rahman and Stillinger.

ISSN:0026-8976    

DOI:10.1080/00268977700100921

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor