摘要:

Results of molecular dynamics simulations on liquid SO2are reported. Four effective pair potentials of different level of sophistication have been tested in order to reproduce the thermodynamic data along the liquid-vapour coexistence curve. The structural properties are investigated and compared with recent experimental data. The self diffusion coefficient is also computed for each potential model.

ISSN:0026-8976    

DOI:10.1080/00268978500102291

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Site jump models are often used to interpret spectroscopic effects of molecular motions occurring in the presence of potential wells. Continuous diffusion equations, albeit complex to handle, are expected to give a more detailed picture of the dynamics and to provide molecular interpretation of the kinetic parameters. In the paper we show how the results of random walk models can be recovered from the correct solutions of the diffusion equations. To this purpose, two routes are followed. First, a procedure is developed for the exact calculation of the time integral of pertinent correlation functions, to be compared with the time constant for the kinetic process of interest. Secondly, the asymptotic solutions of the diffusion equations, valid in the limit of high potential gradients, are used to derive ‘localized functions’, which lead quite naturally to master equations for jumps among discrete sites. Rotational diffusion in uniaxial liquid crystals, translational motions across smectic layers, hindered internal motions and conformational changes are considered as physical examples of relevant experimental interest.

ISSN:0026-8976    

DOI:10.1080/00268978500102301

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Using the new crossed neutral molecular beam apparatus which has been constructed at the University of Minnesota, an extensive study was made of the interaction of an HBr beam with a chlorine beam containing small polymers. It was possible to resolve the van der Waals bond exchange reaction of HBr with chlorine trimer to form HBrCl2. Angular and velocity distributions of scattered HBrCl2, (Cl2)2, and Cl2have been measured and transformed to provide centre-of-mass flux contour maps. The HBrCl2is observed as a single narrow peak, scattered backwards with respect to the initial motion of the HBr. A portion of the scattered Cl2can be attributed to this reaction, which is observed to exhibit a significant fraction (∼ 50 per cent) of the available energy in product translation. A portion of the scattered (Cl2)2can be attributed to a separate collision-induced dissociation process of the (Cl2)3. A simple model is proposed for the collision processes of HBr + (Cl2)3which consistently explains all the dynamical behavior observed.

ISSN:0026-8976    

DOI:10.1080/00268978500102311

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Spin-lattice relaxation times have been measured for the fluorine nuclei in gaseous WF6, MoF6and UF6as a function of temperature in the dilute gas region. The measured temperature dependences are as predicted for relaxation resulting from a spin-rotation interaction. Effective cross sections for the transfer of angular momentum to molecular rotation during collisions are deduced.

ISSN:0026-8976    

DOI:10.1080/00268978500102321

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

HeNe laser measurements of the magnetic birefringence of gaseous nitrogen monoxide in the temperature range between -85 and 120°C and at different pressures below 1·4 bar are reported and analysed in terms of a semiclassical quantum statistical theory. The polarizability anisotropy, Δα = α‖ - α⊥ = 0·844(10) × 10-24cm3, the anisotropy of the first magnetic hyperpolarizability, Δβ = β‖- β⊥= 3·3(6) × 10-33cm3G-1, and the corresponding parameter of the second hyperpolarizability, Δη = -2·9(32) × 10-42cm3G-2, were obtained for the2Π ground state while constraining the zero-field molecular parameters and theg-factors to the known spectroscopic values and the magnetic susceptibility anisotropy to ζ‖- ζ⊥= -17·2(8) × 10-30cm3which was derived from other sources. Δβ is the first numerically known parameter of this kind. Δα agrees with literature Rayleigh scattering results which indicates that the imaginary contribution to the polarizability tensor of NO is negligibly small.

ISSN:0026-8976    

DOI:10.1080/00268978500102331

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The explicit numerical solution of the Generalized Mean Spherical Approximation (GMSA) for a two-component hard sphere mixture is obtained by employing an iterative procedure which starts from the known analytic Percus-Yevick (PY) result. The parameters which enter the theory are fitted to a set of thermodynamic data generated from parametrized forms of computer simulation results, so as to ensure the thermodynamic consistency of the theory. The radial distribution functions so obtained compare very favourably with the available Monte Carlo results, and systematically improve on the PYgij(r).

ISSN:0026-8976    

DOI:10.1080/00268978500102341

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A new three parameter pair potential for argon is suggested. Its parameters are determined from fitting it to data of the second virial coefficient and the throttling coefficient. Excellent predictions are achieved for the viscosity. The third virial coefficient and liquid state data are obtained in very good agreement with experiment when the Axilrod-Teller-forces are included with the strength coefficient determined from the pair potential parameters. The new potential, referred to as the MSK, is as suitable for the correlation of the thermophysical properties of argon as the complicated Barker-Fisher-Watts-potential. It is hoped, therefore, that it will prove to be a simple flexible potential function for other forms of isotropic interactions as well.

ISSN:0026-8976    

DOI:10.1080/00268978500102351

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The excitation of chlorine Cl2by He(23S), He(21S) atoms in comparison to HeI photon impact is investigated by electron and optical spectroscopy. Both types of measurements are performed simultaneously in the same molecular beam machine. All data presented are either the first of their kind or improve existing measurements.

ISSN:0026-8976    

DOI:10.1080/00268978500102361

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

An in-plane crossed molecular beam apparatus has been used to measure the methane-methane total differential scattering cross section. A clearly resolved rainbow oscillation enables an effective isotropic well depth to be determined rather accurately. The data is analysed using a number of spherical and anisotropic potential functions and is also fitted to an analytic semiempirical spherical model. None of the potentials currently in the literature give scattering cross sections and second virial coefficients which are in good agreement with experimental data.

ISSN:0026-8976    

DOI:10.1080/00268978500102371

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effect of the variation of the quadrupole moment on the intermolecular potential has been studied for N2, CO2and CS2. Results are reported for the dimer potential surface and for liquid state properties as obtained from molecular dynamics simulation.

ISSN:0026-8976    

DOI:10.1080/00268978500102381

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor