摘要:

An investigation of the orientational correlation in the liquid halogens is presented. Starting from the structure of the solid we were able to show that the short range structure of the liquid halogens is dominated by orientational correlation similar to those found in the solid. We also performed an experimental investigation of the structure factor of Br2at 200°C; these results, together with those available in Cl2at an equivalent temperature, allowed us to establish that the structure of liquid halogens is rather temperature independent.

ISSN:0026-8976    

DOI:10.1080/00268978500100211

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

In order to examine the application of the Landau-Zener (LZ) approximation to atom-diatom collisions, the electronic transition induced by a strong laser field is considered for the F(2P3/2), F(2P1/2) + H2+hθ systems. Comparison between the LZ transition probabilities and those obtained by numerical solution of the exact semiclassical (SC) equations demonstrates significant differences, the most important being found in the case of the F(2P1/2) + H2+hθ,hθ = 0·117 eV system, where the LZ probability changes smoothly with translation energy, while the SC probability has deep minima.

ISSN:0026-8976    

DOI:10.1080/00268978500100221

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The coupled1H and13C nuclear magnetic relaxation in dichloromethane has been studied in acetone and deuterated acetone. The dynamical parameters have been found to be the same in the two media (Dxx= 4·1 × 10-10,Dyy= 2·0 × 10-10Dzz= 8·6 × 10-10s-1). The ratio of the random field spectral densities in the two solvents is lower than the theoretical value. This discrepancy has been ascribed to the different internal dynamics of the CD3and CH3groups. The isotopic content of the medium is shown to affect the relaxation times of the proton as well as the carbon nuclei.

ISSN:0026-8976    

DOI:10.1080/00268978500100231

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Formal inversion methods are derived by means of which pair potential energy functions may be determined directly from observable thermophysical properties for molecules of spherical symmetry. In the case of dilute gas transport properties and second virial coefficients, the derived procedures are shown to be entirely equivalent to the iterative inversion methods which have been successfully applied to these properties but whose justification to date has been largely empirical. They are here given a sound theoretical basis and their main characteristics are explained. The approach presented here may be used to develop similar inversion methods for other properties and to understand what information about non-spherical pair potentials may be obtained by applying these techniques to data for polyatomic molecules.

ISSN:0026-8976    

DOI:10.1080/00268978500100241

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The formal data inversion methods developed for spherical systems in the previous paper are used to devise similar techniques for non-spherical molecules. These are shown to be entirely equivalent to the heuristic methods of Smith and co-workers recently applied to polyatomic systems. The specific cases of second virial coefficients and dilute gas transport coefficients within the Mason-Monchick approximation are considered. The nature of the average over the full potential energy surface which is obtained by inversion is identified. The procedures are applied to molecules interacting with anisotropic inverse power potentials, for which analytic solutions are possible. This gives further insight into the relationship of the inverted potential to the true function. The results are consistent with observations reported in inversion studies involving more realistic non-spherical potentials. The implications of the results for obtaining information about the anisotropy of potential energy surfaces are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978500100251

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We have applied a recently developed statistical mechanical theory for the interfacial properties of strongly anisotropic fluids to the liquid-vapour interface of a model nematic at the triple point temperatureTtr, i.e. at the nematic-isotropic transition under conditions of saturated vapour pressure. We have investigated the structure of the interfacial region, and in particular we have studied the dependence of the orientational order parameter profiles on the details of the intermolecular potential characterizing the system. We find that both parallel and perpendicular orientations of the molecules at the nematic free surface can be obtained, depending on the sign of one of the parameters that specify the interactions, in qualitative agreement with experimental results.

ISSN:0026-8976    

DOI:10.1080/00268978500100261

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

An evolving wavepacket study has been made of the rate of radiationless transition from a linear excited electronic state of a triatomic molecule to a lower dissociative bent state, brought about by vibronic interaction (the Renner-Teller effect) where both states correlate with a Π state in the linear configuration. The rate is found to increase (i) with decrease in the quantum number π2of the upper state bending vibration, (ii) with increase in the quantum numberKfor the axial component of the total rotational angular momentum, and (iii) with increase in the divergence between the two Born-Oppenheimer potential curves upon bending. There is a maximum crossing probability of 50 per cent during one half-period of the bending vibration.

ISSN:0026-8976    

DOI:10.1080/00268978500100271

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Two photon excitation, tunable near 248·5 nm, has been used to dissociate H2O/D2Oviathe[Ctilde]1B1and[Btilde]1A1states. Rotationally resolved OH/OD(A2Σ+) photofragment excitation spectra are reported, following excitation to predissociated levels of[Ctilde]1B1. Rotational resolution of the OH/OD(A2Σ+→X2Π) fluorescence, generated from individualJ′K a K clevels of[Ctilde]1B1, allows full quantum state selection in both the entry and exit channels. The OH/OD(A2Σ+) fragment is formed rotationally hot as a result of the large change in bond angle in going from[Xtilde]1A1(or[Ctilde]1B1) to the linear dissociative[Btilde]1A1surface. Product alignment measurements allow assignment of the two photon continuum absorption to[Btilde]1A1:a-axis rotation in[Ctilde]1B1destroys product alignment from these levels. Electronic branching from ⪷B1A1toÃ1B1(and/or[Xtilde]1A1) during the dissociation forms ground state OH/OD(X2Π). Relative branching ratios are obtained and display a strongK′adependence.

ISSN:0026-8976    

DOI:10.1080/00268978500100281

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268978500100291

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The nature of adsorption at the interface between a model binary fluid mixture and a solid substrate is investigated using a two-density free-energy functional. For model fluids which exhibit a liquid-liquid upper critical end point we show that the solid-vapour interface can be wet by a ‘double’ wetting film which is a composite of both phase-separated liquids. The structure and growth of such composite films is described and their possible observation discussed briefly. Results of calculations of the density profiles, relative adsorption and surface tension of the solid-vapour interface are presented. For certain choices of the substrate-fluid potential the binary fluid can exhibit re-entrant partial wetting as the temperature is increased, i.e. the solid-vapour interface undergoes transitions from partial wetting, to complete wetting by one liquid phase, to partial wetting and, finally, to wetting by the common liquid phase that occurs above the critical end point.

ISSN:0026-8976    

DOI:10.1080/00268978500100301

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor