摘要:

Highly resolved emission and excitation spectra of phenalenyl are reported. Our semiempirical calculations predictE″ symmetry for the lowest excited state. Indeed, Jahn-Teller effects are observed. Force field calculations have been performed to determine the symmetries of vibrations visible in the spectra. The Jahn-Teller coupling is analysed with a scheme of Sloane and Silbey.

ISSN:0026-8976    

DOI:10.1080/00268978400100381

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Valence ionization energies of the short-lived radicals OH and OD formed in the gas phase reaction between fluorine atoms and (deuterated) water are presented. The essential role of a new modulation method, used in combination with discharge-triggering, lock and multiscan techniques, in ultraviolet photoelectron spectroscopy of transient species generated by atom-molecule reactions is illustrated. Results are in excellent agreement with data from optical emission spectroscopy which have either been obtained experimentally or have been inferred from spectral perturbations. As secondary reaction products, the unstable molecules HOF and DOF are detected.

ISSN:0026-8976    

DOI:10.1080/00268978400100391

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A six-site model is developed for the intermolecular potentials of the azabenzene molecules by analysing their crystal structures. The potential includes anisotropic functions on the C and N sites to represent the effects of the bonded H atoms and the lone pair electron density, and can predict the crystal structures of benzene, pyridine, pyrazine, pyrimidine, s-triazine and s-tetrazine within a few per cent.

ISSN:0026-8976    

DOI:10.1080/00268978400100401

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Solutions of the time-dependent Schrödinger equation, in the semi-classical electric dipole approximation, are developed for the interaction of a two-level system, possessing both transition and diagonal dipole matrix elements, with applied static and sinusoidal electric fields. Exact solutions can only be obtained subject to conditions involving the orientations and strengths of the applied fields. These, and perturbative extensions, are used to discuss some of the features of multi-photon processes that depend on the existence of non-zero diagonal dipole matrix elements. Some of the results apply, in the limit of vanishing permanent moments, to the atomic two-level problem.

ISSN:0026-8976    

DOI:10.1080/00268978400100411

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The coupled relaxation of the Zeeman and tunnel systems of methyl groups has been studied by N.M.R. spectroscopy in powdered pentamethyl-benzene at temperatures below 15 K, in the magnetic field range 0-2 T. The observed rapidity, saturation and recovery of the resonance confirm theoretical predictions of Nijman, Sprik and Trappeniers [12] for (X-H4) substances, and the equivalence of their theory adapted by us to methyl groups using the simplified relaxation model of Emid and Wind [4] is established. Reasons for the semi-quantitative agreement between theory and experiment are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978400100421

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A neutron scattering experiment has been performed on a CHCl3/CDCl3sample with zero coherent scattering length for hydrogen. The study performed at 20°C with two different wavelengths (0·7 and 0·5 Å) allowed a detailed investigation of the data analysis procedure. In particular the inelasticity correction to self scattering has been computed on the basis of monoatomic gas model. One has also found that in the case of strong inelasticity the multiple scattering became angular dependent. The fully corrected coherent differential cross section was separated into an intra- and an intermolecular part from which the molecular parameters were determined.

ISSN:0026-8976    

DOI:10.1080/00268978400100431

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The results of SCF calculations for a water molecule interacting with (1) sodium and (2) chloride ions are presented. Sufficient points have been calculated to allow full details of the potential surfaces to be seen. Analytic models which fit the calculated points accurately have been obtained.

ISSN:0026-8976    

DOI:10.1080/00268978400100441

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

An integral equation for the full particle-particle correlation functions in molecular fluids is obtained by expressing the relevant quantities in terms of the graphical language of the interaction site formalism. The equation is of the form of the Ornstein-Zernike equation for an atomic mixture, but is mathematically equivalent to the ‘proper’ integral equation of Chandler, Silbey, and Ladanyi. The simple form results in part from the introduction of a convenient method which yields the topologically correct interaction site graph chain sums. Further, by direct analogy with the usual graphical analysis of atomic fluids, we obtain a closure relation which is formally exact in the same sense as that in the usual atomic theory. Numerical results obtained using closures which are the graphical analogues of the usual atomic Percus-Yevick and hypernetted chain approximations are discussed for model homonuclear Lennard-Jones diatomic fluids. These preliminary results suggest that such direct generalizations are not likely to provide improvement over RISM results.

ISSN:0026-8976    

DOI:10.1080/00268978400100451

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

This paper reports upon new studies of the error involved in the superposition approximation to the triplet distribution functiong3in atomic fluids. The analysis is performed by first expressingg3in spherical perimetric coordinates (ρ, θ, φ) in which the ‘size’ of a triangle, ρ, is measured independently of its ‘shape’ θ and φ. Theng3is expanded in spherical harmonics of the triangular shape parameters. The expansion coefficients were evaluated by analysing molecular dynamics simulation data for a Lennard-Jones fluid and the results were compared with the corresponding coefficients appearing in an explicit expansion of the superposition approximation. We show how these two sets of coefficients may be combined to give a precise representation of the difference between the simulation and the superposition correlation functions. This formulation is then tested by evaluating the Axilrod-Teller triple-dipole energy directly from simulation and from the superposition approximation plus correction terms.

ISSN:0026-8976    

DOI:10.1080/00268978400100461

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The four low frequency fundamentals of74GeH3F gives rise to two pairs of Coriolis-coupled vibrationally excited states; the infrared bands due to these states have been studied at an effective resolution of about 0·06 cm-1and interpreted in terms of a simple model involving three interacting upper state levels, and also in terms of an extended model including interactions between upper state levels for which (k-l) differs by ± 3. The infrared data are fitted satisfactorily by the simple model, but inclusion of pure rotation spectra in the data set makes it possible to define one parameter relating to the extended model. The sign of the perturbation ofv3andv6is found to be negative; that of the interaction betweenv2andv5cannot as yet be specified, because the two vibrational states lie very close in energy, the vibrational origins differing by only 0·155 cm-1. The magnitudes of thez-axis andy-axis Coriolis coupling constants determined from the analysis of the spectra allow most of the off-diagonalFmatrix elements of the harmonic force field for74GeH3F to be specified.

ISSN:0026-8976    

DOI:10.1080/00268978400100471

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor