摘要:

An experimental field-time two-dimensional transient E.S.R. method is presented, together with the first two-dimensional E.S.R. spectrum of this type. A comparison of transient E.S.R. methods is given along with a new variation on the time-integration spectroscopy (TIS) method involving the interposition of a microwave delay period between creation and observation of the radicals. This MISTI (microwave switched time integration) technique is shown to increase the signal-to-noise ratio of spectra obtained at times somewhat after radical creation considerably. It is concluded that continuous-wave methods using digital sampling offer the highest resolution and signal-to-noise ratios of the existing techniques under most conditions, and that continuous-wave and pulsed techniques have similar time-resolutions.

ISSN:0026-8976    

DOI:10.1080/00268978600100181

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

New interpolation equations are given for some typical integrals over pair- and triplet-correlation functions of a Lennard-Jones (12–6)-fluid. These integrals extend over a large region of states and can easily be differentiated with respect to density and temperature. The integrals over the triplet-correlation function were simulated in Monte Carlo calculations, thus avoiding the use of the superposition approximation. The performance of this approximation is briefly discussed.

ISSN:0026-8976    

DOI:10.1080/00268978600100191

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

We report a systematic study of the reactions of Xe(3P1,3P2) with HCl, HBr and HI using both spectroscopic and molecular beam techniques. No reaction is observed at room temperatures for Xe(3P2) with HCl; analysis of the Xe(3P1)/HCl data yields an estimate of the endoergicity of the3P2reaction which agrees within experimental error with the threshold obtained from deconvolution of the excitation function measured in the molecular beam experiments, thus indicating little or no barrier in the entrance channel. Surprisal analysis of the vibrational population distributions obtained by inversion of the rare gas halide spectra yields estimates for the fraction of the available energy disposal into vibration <fv>. The results are in broad agreement with earlier estimates and are roughly independent of the spin orbit component for a given reaction. Deviations from the purely kinematic limit in the product rotational alignment (<P2(Ĵ′ . [kcirc])>) increase across the series HCl, HBr, HI while <fv> remains moderate, ∼0·5. These results taken with the backward scattering observed for the inelastic channels at low collision energies in the Xe(3P2)/HBr system and the indication of a preferred angle of attack as evidenced by the opacity functions for this system suggest that reaction proceeds via a bent transition state lying towards the product region of the potential energy surface with an important contribution from repulsive release of exoergicity in the exit channel. Similar trends have been observed in the analogous reactions of alkali metal atoms with the hydrogen halides.

ISSN:0026-8976    

DOI:10.1080/00268978600100201

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Neutron diffraction data on seven different isotopes of formamide, containing1H and2H, are reported. Background, self-absorption of the sample and container and multiple scattering corrections were done in the previous way, whereas a new empirical procedure for the inelasticity correction is presented. After separation of the coherent scattering contribution into intramolecular and intermolecular parts the latter was analysed in terms of four expansion coefficients of the molecular pair-correlation function. These give information about the molecular centre-centre distributions and orientational correlations. It is found that in the first neighbour sphere at 4.2 Å an antiparallel orientation of the molecules is preferred, whereas a parallel orientation prevails at 5.1 Å.

ISSN:0026-8976    

DOI:10.1080/00268978600100211

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A method for the evaluation of the second virial coefficient of two-dimensional dumbells and polyatomics and their mixtures is proposed. The method employs an exact relationship for the hard convex figure mean area; the way of calculating small differences in the mean areas of the fused hard-disc model and the corresponding hard convex figure is shown and exemplified for five models. The use of a hard convex figure equation of state for the above figures is discussed and its extension to mixtures is given.

ISSN:0026-8976    

DOI:10.1080/00268978600100221

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Electrochromism analyses of anthracene, 9,10-dimethylanthracene 1,6-diphenyl-1,3,5-hexatriene and perylene in polyethylene matrices are given. Previous studies of the second rank order parameters of some of these molecules in a lyotropic nematic phase are included. A simple model, which on the basis of the electrochromism results, explains the observed discrepancy between order parameters in ground and excited states is presented. It is found that the changes in anisotropic polarizability upon excitation are contributing significantly to the reorientation of an excited molecule.

ISSN:0026-8976    

DOI:10.1080/00268978600100231

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In order to derive the Smoluchowski, Fokker-Planck and Langevin equations, that so often form the starting point for theoretical work on the properties of suspensions of brownian particles, it is necessary to assume time-scale separations between the decay times of correlation functions of the particles' positions, those of their momenta and those of the fluid forces acting on them. We re-examine whether these assumptions can be justified for a normal, experimental set-up, and we conclude that for concentrated suspensions, where the volume fraction of brownian particles is not negligible, there are good reasons for thinking that in fact the assumptions are not necessarily valid. We finally briefly indicate how one might set about deriving more complex but hopefully better justified equations to treat such systems.

ISSN:0026-8976    

DOI:10.1080/00268978600100241

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

We show that the evaluation of electron energy spectra which result from autoionization of a collision complex may result in rather detailed information on the electronic structure and on the dynamics of the complex.

ISSN:0026-8976    

DOI:10.1080/00268978600100251

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The principal purpose of this paper is to give an unambiguous test of the self-consistent mean field (SCMF) theory for a fluid of polarizable Lennard-Jones particles with dipoles and quadrupoles. The SCMF approximation replaces the many-body interactions present in polarizable fluids with an effective pair potential, and relates the properties of the system of interest to those of the effective system. In the present work the properties of the effective system are obtained using exact molecular dynamics (MD) calculations and the SCMF/MD results are compared with full MD simulations of the polarizable fluid. This procedure eliminates ambiguities present in previous calculations due to approximate theoretical treatments of the effective system, and provides a clear test of the SCMF reduction of the many-body potential. Also given is a general derivation of the SCMF result for the dielectric constant which is independent of the way in which the properties of the effective system are obtained. Finally, the time correlation function <M(t),M(0)>, whereMis the total dipole moment of the sample, is calculated and compared with earlier results for different models.

ISSN:0026-8976    

DOI:10.1080/00268978600100261

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268978600100271

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor