摘要:

A new and improved method is presented for computer simulation of collision-induced far-infrared absorption spectra of atomic and molecular species. The improvements involve (a) eliminating redundancy in the statistical sampling of the molecular trajectories, and (b) transforming the integrals for the orbital variables so that the singularities of the integrands at the turning points are eliminated. An asymptotic theory of the line shape developed earlier for atomic spectra is extended to molecular spectra. Results are given for the atomic species, due to overlap induction, at the reduced temperaturesT* = 1, 2, 4, 5, 10, 15, and for the molecular species, due to quadrupolar, octopolar and hexadecapolar induction, atT* = 1, 2, 4. The agreement between the simulated and theoretical spectra is excellent.

ISSN:0026-8976    

DOI:10.1080/00268978700100641

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The graphs of the virial expansion of the grand potential of molecules in a spherical cavity are related to the graphs of the virial coefficients of a homogeneous gas mixture. The second virial coefficient is obtained for hard spheres in a spherical cavity with a square-well wall, and for square-well molecules in a cavity with a hard wall. The planar limit of these results is used to analyse several different proposals for separating the grand potential into a bulk and surface part for arbitrary wall potentials. It is shown that none of these is entirely satisfactory and that, for systems of arbitrary geometry, no unique division is possible.

ISSN:0026-8976    

DOI:10.1080/00268978700100651

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Reduced characters for a finite groupGwith respect to a subgroupG0, are defined by taking partial traces with respect toG0-invariant subspaces of the irreducible representations ofG. The properties of reduced characters and their evaluation is discussed in detail and in particular a complete theory of reduced characters for simply reducible subgroup imbeddings is developed. In the general case the reduced characters ofGcontain all multiplicity-independent information about the imbeddingG⊇G0. We apply our methods to the evaluation of all multiplicity-averagedG:G0reduced Wigner coefficients which include, as a special case, all multiplicity-free reduced Wigner coefficients. It is shown that these coefficients are intimately connected with the algebra structure ofG0-class functions onG.

ISSN:0026-8976    

DOI:10.1080/00268978700100661

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A new generalized diffusion equation is derived for a suspension of interacting axisymmetric brownian particles subjected to a time-dependent external field. Explicit molecular expressions are obtained for the generalized Onsager mobility tensors. Because of the external field, additional ‘field’ mobilities appear in the theory. These can be related but not totally reduced to the Onsager mobility tensors. For translationally invariant systems a separate equation is obtained for the orientational distribution of brownian particles. This equation is a generalization of the familiar Debye equation applicable to interacting axisymmetric particles. The generalized rotational diffusion equation is found to be non-local with respect to the orientational variable. A simple quasihydrodynamical model is used to obtain estimates of the mobility tensors.

ISSN:0026-8976    

DOI:10.1080/00268978700100671

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The analysis of the energy level data available for Cs2NaErCl6is given, the mean error in fitting 31 levels being 16·4 cm-1. The eigenvectors obtained from the calculation are used to compute spontaneous emission probabilities and line intensity ratios for the4I13/2→4I15/2magnetic-dipole transitions of Er3+in Cs2NaErCl6. The liquid-helium-temperature infrared luminescence spectrum for this transition of ErCl3-6in cubic elpasolites is reported for the first time and the line locations and relative intensities are in agreement with calculation.

ISSN:0026-8976    

DOI:10.1080/00268978700100681

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The analysis of the microwave spectrum of thegaucheform of 2-methoxyethylamine has been extended to highJhighK-1transitions.A-Esplittings due to the methyl group internal rotation have been measured in the ground state and in some torsionally excited states due to the skeletal torsions. A flexible model treatment of the microwave data led to the reassignment of some torsional satellites and to the interpretation of the ordering of theA-Esublevels.

ISSN:0026-8976    

DOI:10.1080/00268978700100691

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Application of a strong de electric field to solutions of apolar molecules in an apolar solvent leads to partial orientation of the molecules. This orientation could be detected by N.M.R. spectroscopy through the anisotropic spin interactions that show up in the spectra. Subsequent analysis of the spectrum leads to information about the static electric polarizability tensor (a). The electric field N.M.R. (EFNMR) method was applied to measure, from the2H EFNMR spectrum of naphthalene-d8, the anisotropy ofa(i.e. Δα), and asymmetry (δα). The result is: 7·1 ± 0·3 and -(4·4 ± 0·5) × 10-24cm3for Δα and δα respectively. For triphenylene-d12the value of Δα is measured to be -(14·4 ± 1·4) × 10-24cm3. The results from the EFNMR method and from other methods are compared and discussed

ISSN:0026-8976    

DOI:10.1080/00268978700100701

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The vapour of an ionic fluid at low temperature is known to be dominated by ion pairs and larger neutral clusters with smaller populations of individual ions and charged clusters. Previous cluster treatments of the restricted primitive model are improved to include clusters through the hexamer and to consider interactions between clusters according to the mean spherical approximation. With these refinements it is possible to obtain good results for reciprocal reduced temperatures β* from 6·8 to 20 which include the critical temperature. The distribution among clusters and various thermodynamic properties are calculated. The concentration of charged clusters is reported for comparison with measurements of electrical conductance. Since the approximations of this approach become serious at reduced densities (c* = Na3/V) above 0·02, interpolations are made with an empirical equation of Larsen based in turn on various Monte Carlo simulations. These interpolations yield estimates of the saturated liquid and vapour densities and a critical β* of 14·7. The speculative nature of the estimates of critical properties is emphasized.

ISSN:0026-8976    

DOI:10.1080/00268978700100711

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The Raman spectra of thev1(CN) stretching mode of SCN-ions have been measured in molten thiocyanates, KSCN and NaSCN, at temperatures 450-600K. The vibrational and the rotational correlation functions are calculated, and the dynamics of SCN-ions in the molten state are compared with those in aqueous solutions of KSCN, NaSCN, and LiSCN at concentrations 1–10 mol dm-3and at temperatures 303–353 K. The observed vibrational correlation functions are analysed by the stochastic line shape theory of Kubo, in which homogeneous and inhomogeneous broadening are treated simultaneously. Both broadening contributions to the isotropic spectra are extracted. The homogeneous broadening is found to increase with increasing temperature in both melts and aqueous solutions; the inhomogeneous broadening remains constant in molten KSCN while it decreases in aqueous solutions. As the result, the isotropic Raman bandwidth is considered to increase with temperature in the molten state and to decrease in aqueous solutions. Rotational correlation functions of SCN-ions in these molten salts show the behaviour of the short time inertial rotation (t⪅ 0·15 ps, jump angle 20°), which is a little slower than the free rotation of a single ion. The long time exponential decay of the rotational correlation functions reflects the ultimate diffusional behaviour of the ionic reorientation. The rotational relaxation rate increases with increasing temperature in both melts and aqueous solutions. The vibrational dephasing rate decreases and the rotational relaxation rate increases as the cation size increases in melts. In aqueous solutions, the vibrational dephasing rate follows the same cation dependence as that in melts, while the rotational relaxation rate decreases as the cation size increases. This seems to be a consequence of the specific local structures in aqueous electrolyte solutions.

ISSN:0026-8976    

DOI:10.1080/00268978700100721

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We study the Hall effect for ions in dilute electrolyte solutions. We employ a continuum model and hydrodynamic equations which involve electric and magnetic force terms. We find that for slip boundary conditions the Lorentz force on an ion in a strongly polar liquid is reduced by about 25 per cent.

ISSN:0026-8976    

DOI:10.1080/00268978700100731

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor