摘要:

The observation of electron spin polarized spectra from free radicals using flash-photolysis electron spin resonance methods is described. The origins of polarization are summarized and a critical account of their present understanding provided. The phases of the polarized signals carry information on the multiplicity of the radical precursor. Examples are provided from observations of nitrogen heterocyclic radicals of the use of the spectra to obtain such information, and to identify reactive states precisely.

ISSN:0026-8976    

DOI:10.1080/00268978500100011

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Vibration rotation spectra of HO15NO and DO15NO have been measured at a resolution of 0·04 cm-1to determine the isotopic shifts in the vibrational band origins. These have been used together with recently determined data on the vibrational band origins, Coriolis constants, and centrifugal distorition constants, to determine the harmonic force field of both cis and trans nitrous acid in least squares refinement calculations. The results are discussed in relation to recentab initiocalculations, the inertia defects, and the torsional potential function.

ISSN:0026-8976    

DOI:10.1080/00268978500100021

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The prediction by Cahn (1977,J. chem. Phys.,66,3677) that a two phase fluid at a wall shows a wetting transition accompanied by a thick-thin film (prewetting) transition as the temperature increases towards the critical value where the fluid becomes uniform has been supported by a number of workers using free energy density functional theory. Due to the use of strong and varying approximations the support is of a qualitative nature and, in the absence of simulation verification of wetting-prewetting in simple solid-fluid systems, the quantitative aspects of the phenomenon are controversial. In this work we apply the GvdW functionals, previously successfully applied to both adsorption and gas/liquid interfaces in simple fluids to the wetting problem. The system consists of a carbon dioxide wall represented as a uniform continuum and an argon fluid interacting within itself and with the wall by appropriate Lennard-Jones (12–6) potentials. We focus our attention on the role of non-local entropy (responsible for hard-sphere oscillatory liquid structures) in the wetting phenomenon. The results of both semianalytical analysis based on the use of step-function fluid profiles and numerical optimization techniques yielding realistic profiles indicate that non-local entropy and the corresponding oscillatory structures play an important role in wetting by dropping the wetting temperature and stretching the prewetting line at which the thick-thin film transition occurs.

ISSN:0026-8976    

DOI:10.1080/00268978500100031

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Reactive scattering of Cl atoms with C3H7I molecules has been studied over the range of initial translational energyE= 46-25 kJ mol-1, using a supersonic beam of Cl atoms seeded in He and Ne buffer gas. Laboratory angular and velocity distributions of ICl product were measured which show reaction proceeding via a long-lived collision complex at low initial translational energy. However a forward scattered component with a higher product translational energy appears at intermediate and higher initial translational energy. The decreased lifetimes for complexes formed in large impact parameter collisions and the high product translational energies reflect the reduced density of vibrational states prevailing for complexes with large values of the total angular momentumJ≲ 300 ħ.

ISSN:0026-8976    

DOI:10.1080/00268978500100041

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Reactive scattering of Cl atoms with C3F7I molecules has been studied at an initial translational energyE= 47 kJ mol-1, using a supersonic beam of Cl atoms seeded in He buffer gas. Laboratory angular and velocity distributions of ICl product have been measured which show reaction proceeding via a long-lived collision complex. The forward and backward scattering has a higher product translational energy than the sideways scattering, with the intensity and energy of the forward scattering somewhat higher than the backward scattering. Long-lived collision dynamics first break down in collisions at large impact parameters with apparently incomplete energy transfer to internal modes of the C3F7radical.

ISSN:0026-8976    

DOI:10.1080/00268978500100051

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Absolute nuclear shieldings for19F are compared with the temperature dependence in the zero-pressure limit obtained from N.M.R. studies of fluoromethanes in the gas phase. From the correlation between these quantities and between absolute shielding and N.M.R. isotope shifts, it is concluded that σe, the19F shielding at the equilibrium configuration and (δσ/δΔrCF)e, the change in nuclear shielding with CF bond extension, are correlated, (δσ/δΔrCF)ebeing more negative for smaller σe. A similar correlation is deduced for (δσ/δΔrCO)eand13C shielding.

ISSN:0026-8976    

DOI:10.1080/00268978500100061

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Studies of the phosphorescence spectrum of the major NO-2trap in NaNO2/Ag+at < 4K show that non-Condon effects are associated with the progression in the totally symmetric bending mode. These are manifest by different intensity distributions for the contributions of two spin levels of the triplet state to the progression. A standard Franck-Condon analysis of these distributions thereby implies a spin level dependent displacement in the triplet state for the totally symmetric mode. Incorporating a dependence of the electronic transition moment on the normal mode, the different intensity distributions can be explained in terms of more complicated vibrational factors and a spin level independent displacement parameter. The results are qualitatively in agreement with a theoretical model.

ISSN:0026-8976    

DOI:10.1080/00268978500100071

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Complex permittivity measurements in liquid methyl chloride have been completed over the whole frequency range at temperatures and densities scanning the orthobaric curve, from 176 K up to 363 K. A report on the experimental set-ups and the accuracies obtained is given. Relaxation parameters are derived in the frame of Debye theory, and Hill's distribution of damped resonances is used to construct a model for librational absorption.

ISSN:0026-8976    

DOI:10.1080/00268978500100081

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

It is shown that in gases of spherical-top molecules with orbitally degenerate ground electronic terms the orientational mechanism contributes to the generation of birefringence in the presence of a non-uniform electric field. The orientation of molecules by such a field results from the existence of the non-zero quadrupole moments which are available in the molecules under consideration. The contribution to the optical anisotropy arising from the degeneracy has a complicated temperature dependence. At low temperatures, when the ground vibronic state is mainly populated, this contribution is a linear function of inverse temperature as in the case of anisotropic molecules with the symmetry lower than cubic. At intermediate and high temperatures the dependence of the optical anisotropy onTis sufficiently determined by the Jahn-Teller effect taking place when the electronic state has orbital degeneracy. Numerical estimation shows that the effective magnitudes of quadrupole moments of some spherical-top molecules, for example VCl4, ReF6and IrF6(G3/2ground electronic term), are comparable to the quadrupole moments of the diatomic molecules.

ISSN:0026-8976    

DOI:10.1080/00268978500100091

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The polarizabilities describing the response of the multipole moments of a charged harmonic oscillator to a field and field gradient are calculated exactly, without recourse to perturbation theory. Generalizations of the Kirkwood and Unsöld treatments for multipole polarizabilities are given, and found to beexactfor the harmonic oscillator. Changes in the multipole polarizabilities on confinement of the oscillator to a spherical box are also calculated.

ISSN:0026-8976    

DOI:10.1080/00268978500100101

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor