摘要:

The general expressions for the Stokes parameters of an electromagnetic wave of any polarization propagating in an isotropic absorbing medium exposed to a dc magnetic field in the Faraday configuration are derived. Taking into account not only the molecular polarizabilities related to the electric dipole and magnetic dipole but also to the electric quadrupole transitions, the full expression for the quadratic Faraday effect is derived. It is seen that additional, originally unreported terms also play a role, and that the contributions to the effect in fluids are partly independent of the direction of the applied magnetic field relative to the light beam. It is therefore suggested that the effect be reconsidered as quadratic dc magnetic field-induced variation of natural circular birefringence. The chiral molecular symmetries are presented for which the quadratic dc magnetic field induced circular birefringence and dichroism can take place.

ISSN:0026-8976    

DOI:10.1080/002689797171481

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Dressed ion theory, an exact statistical mechanical formalism for electrolyte systems in the primitive model, is extended to electric double layer systems in various geometries. In this theory an exact equation that has the same form as the linearized Poisson–Boltzmann (PB) equation is set up, in which ‘dressed ions’ take the same role in the exact theory as the bare ions have in the PB approximation. Various distribution functions are expressed in terms of the dressed ion charges. Exact asymptotic results for large particle separations are obtained for the distribution functions, the average electrostatic potential and the interaction free energies in colloid dispersions and for planar double layer systems. A practical method is derived for evaluating the effective surface charge densities of the particles. The question of whether double layer interactions between equally charged colloid particles must be repulsive at large separations (as suggested by the PB approximation) or whether they can be attractive there is treated in some detail.

ISSN:0026-8976    

DOI:10.1080/002689797171490

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A previously established method to assign Lennard-Jones parameters for the methyl and methylene site groups in n-alkanes is now generalized to the case of branched alkanes. The method is based on Monte Carlo calculations of the binary cluster integral of the chain molecules, and their comparison with experimental data of second virial coefficients in the gas phase. We have arrived at a single set of values for the parameters epsilon and sigma of the different sites, CH3, CH2, CH and C, that reproduces adequately the virial coefficient data of linear and branched molecules, and also of their mixtures. This way we have also clarified the validity of the different alternative sets proposed in our earlier study for n-alkanes.

ISSN:0026-8976    

DOI:10.1080/002689797171508

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Density profiles and adsorption isotherms of an associating fluid with four bonding sites near a solid surface are investigated using the Percus–Yevick approximation for the associative Henderson–Abraham–Barker equation. The fluid molecule is represented as a hard sphere with four independent attractive sites. The surface is modelled as a hard wall and also as an adhesive wall. The density profiles are obtained both numerically and analytically (as the Laplace transform) as functions of bulk number density η and of the reduced inverse temperatureβ*. The features connected with increasing average numbernbof bonds are discussed. An analytical expression for the adsorption coefficient is derived. Since the system exhibits critical behaviour, the gaseous and liquid branches of both the adsorption isotherm and density profiles are described separately. The density profiles and adsorption isotherms are compared with Monte Carlo simulation data. In the case of an adhesive surface the competition between the adhesion and association is studied. The formation of several gaseous adlayers at the wall is demonstrated.

ISSN:0026-8976    

DOI:10.1080/002689797171517

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The gas-phase infrared spectra of natural CH2= CHCl and monoisotopic CH2= CH37Cl(isotopic purity, 95%) have been investigated in the υ7band region near 1030 cm-1, at Doppler-limited resolution, employing a tunable diode laser spectrometer. This vibration of symmetry species A 'is expected to give rise to ana/bhybrid band, with a predominant contribution of the a-type component. A rovibrational analysis led to the identification of more than 1100 (J≤ 51,Ka≤ 12) and 1000 (J≤ 47,Ka12) transitions belonging to the35Cl and37Cl isotopomers, respectively. The band was found to be affected by different perturbations, and avoided crossings due to the second-ordera-Coriolis resonance with the υ9+ υ12combination also were observed. After using Watson's A-reduction Hamiltonian in theIrrepresentation, the assigned transitions provided a set of effective upper state constants for both the isotopic species.

ISSN:0026-8976    

DOI:10.1080/002689797171526

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Ab initiopotential energy curves and coupling matrix elements of the molecular states involved in the collision of theB2+multicharged ion on atomic hydrogen have been obtained by means of configuration interaction methods. The total and partial electron capture cross-sections for theB2+/Hsystem have been determined using a semi-classical method in the 0·1–190 keV laboratory energy range. The results show a strong effect due to rotational coupling. They improve markedly on previous theoretical work and are in general agreement with experimental data.

ISSN:0026-8976    

DOI:10.1080/002689797171535

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The rovibrational dynamics of a highly excited asymmetric triatomic molecule have been investigated using semiclassical and quantum mechanical methods. The rotational energy surface (RES) has been calculated exactly from the rigid-bender model of the molecule. The RES topology has been studied and the bifurcation of its critical points has been found at a certain critical value of the angular momentum. A reorganization of the energy level structure, due to a change of the RES topology, has been revealed.

ISSN:0026-8976    

DOI:10.1080/002689797171544

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A lattice model is presented for the investigation of orientational and conformational transitions in thin Langmuir films of bipolar surfactant molecules. The model is developed to describe the molecular structure of thin surfactant films at the liquid–vapour interface. Molecular density distribution profiles are examined for different conformational states and surface pressures. The effect is studied of the position of a second polar group along the surfactant molecule chain on the surface area isotherms. The film's collapse into a multilayer state is investigated and an interpretation at the molecular level is given of the collapse transition. Results are compared with data from continuous models for the liquid–surfactant–vapour interfaces.

ISSN:0026-8976    

DOI:10.1080/002689797171553

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

It is known from experimental evidence that, at ambient temperature and under high pressures, the linewidth of the Raman Q branch of nitrogen diluted in helium is considerably less than that of pure nitrogen. Molecular dynamics simulations have been used to explore this phenomenon. For that purpose, a detailed investigation has been made of the various contributions to the vibrational spectrum, and in particular of the time correlations of each of those parts. The results are not only in conformity with the experimental data, but also reveal which molecular properties are responsible for the evident differences between the Raman spectra of the two systems. A strong conclusion is that in the dilute mixture the linewidth is related primarily to the properties of the diluent and to a much lesser extent to the interactions between nitrogen and helium molecules. In fact, a vibrating nitrogen molecule in an environment of helium acts as a probe, signalling intrinsic dynamic behaviour of the helium system. The oscillation in the correlation function of the vibration frequency turns out to be due to a vibration in the mutual forces acting between the atoms and does not arise from the N2–He interaction.

ISSN:0026-8976    

DOI:10.1080/002689797171562

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A Herriott multipass cell has provided a significant increase in the sensitivity of our computer controlled diode laser spectrometer for the investigation of van der Waals clusters in a continuous slit jet expansion. The assignment was then possible of 57 new lines to the perpendicular transition from the (vco,j,Ka,n) = (0,2,2,0) ground state of the Ar—CO van der Waals complex to the combination band of the CO fundamental vibration (vco= 1) and theKa= 1 (j= 1) stretching mode (1, 1, 1, 2). The band origin of 2159·88 cm-1locates the energy of the (1,1,1,2) stretching mode at 26 ·19cm-1. This is the highest van der Waals mode observed in Ar—CO so far. An analysis of the rotational constants resulted in a level ordering of this state relative to the nearby (1, 3, 2, 1) state, which is in contradiction to existingab initiocalculations. The experimental results demonstrate that even these high lying van der Waals modes still show relatively regular behaviour, and therefore will provide a sensitive test for futureab initioand semiempirical potential energy surfaces.

ISSN:0026-8976    

DOI:10.1080/002689797171571

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor