摘要:

A complete hamiltonian for a translating, rotating, vibrating molecule in the presence of a constant external electromagnetic field is derived starting with the Breit equation reduced to a non-relativistic form, correct to orderc-2. A number of new terms appear, which have not been obtained in less precise derivations. These include mass polarization corrections to the orbital Zeeman, spin-orbit and orbit-orbit interactions together with spin-vibration, orbit-vibration and orbit-rotation interactions. In addition there is a vibrational Zeeman interaction which in certain circumstances may be of the same order of magnitude as rotational Zeeman terms. The final hamiltonian provides a starting point for future investigations of the possible effects of these new interactions on the microwave and radiofrequency spectra of both open and closed-shell molecules.

ISSN:0026-8976    

DOI:10.1080/00268977000101471

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Operator methods and Schwinger's perturbation expansion are used in the calculation of thermal averages in molecular physics with regard to gas electron diffraction. These are the partition function, averages of powers of the oscillator occupation number operator <ṋk>therm, the moments of the normal coordinate <[qcirc]k>thermand of the exponential of the normal coordinate <exp[qcirc]>therm. It is shown that the equations developed are quite general, including anharmonic resonances like Fermi and Darling Dennison resonance in polyatomic molecules. Simple algebra is used. A compact and general formulation of the theory of electron diffraction by gases is given, the calculated averages are proportional to the mean radiusrg, the mean amplitudeleand the intensity function <sins[rcirc]/(s[rcirc])>therm. Further applications are summarized. The operator algebra is given in the appendix.

ISSN:0026-8976    

DOI:10.1080/00268977000101481

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The correct quantum-mechanical form for the vibration-rotation bamiltonian of a linear molecule is derived by an extension of the method of Wilson and Howard. The absence of the third rotational degree of freedom complicates the relations obeyed by the angular momentum components in this hamiltonian. Calculations of energy levels can be simplified by transforming to the ‘isomorphic’ hamiltonian introduced by Hougen. The application of this isomorphic transformation to other operators is illustrated with the dipole moment operator.

ISSN:0026-8976    

DOI:10.1080/00268977000101491

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Analysis of the electron resonance spectrum of a paramagnetic probe, vanadyl acetylacetonate, dissolved in a nematic liquid crystal, yields the order for the probe, providing it moves rapidly. As Schwerdtfeger and Diehl have shown, in the absence of molecular motion the sample yields a polycrystalline spectrum and the intensities of the lines now depend on the anisotropic probability distribution function for the probe. The analysis of the angular dependence of the intensities is difficult, but does yield the probability distribution function from which the anisotropic pseudo-potential can be determined. The pseudo-potential for vanadyl acetylacetonate dissolved in a binary mixture of nematogens at - 50°C is mainly a result of repulsive forces. In contrast the pseudo-potential for the probe in a single component of the mixture at room temperature is determined by dispersion forces. This dramatic difference may result from the close proximity of molecules at - 50°C increasing the significance of repulsive forces in comparison to dispersion forces.

ISSN:0026-8976    

DOI:10.1080/00268977000101501

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A simple model is suggested for the empirical description of reactions with activation energy by taking account of orientational requirements for reaction in a hard-sphere model. Reaction probabilities, cross sections and a rate constant are deduced and found to be consistent with extensive Monte Carlo data for the H + H2reaction. The form of agreement is much improved over the model due to R. D. Present, especially for collisions at larger impact parameters.

ISSN:0026-8976    

DOI:10.1080/00268977000101511

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The He-He, He-H(1s), H(1s)-H(1s) and H(1s)-H(2s) interactions are considered as model systems for studying how charge overlap effects in second-order dispersion energies vary as a function of the nature of the interacting species. The non-expanded second-order energy and the corresponding multipoleR-1expansions, through all powers ofR-1, are obtained for each interaction using Unsöld's average energy approximation. The results are used to discuss the limitations of the usefulness of theR-1expansions.

ISSN:0026-8976    

DOI:10.1080/00268977000101521

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Several methods of estimating exchange energies have been tested for the interaction of two hydrogen atoms in 2s, 2p or hybrid valence states. The simplest relationship previously used,X=KS2/R, does not give an accurate picture of the dependence on internuclear distance. A two-term expressionX=S2(AR-1+BR-2) is considerably better but fails for the case of exchange between orthogonal orbitals (S= 0). An alternative expression

ISSN:0026-8976    

DOI:10.1080/00268977000101531

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The intensities of the vibrational components of theA←XandB←Xband systems of NH3have been calculated from vibrational functions appropriate to the best one-dimensional potential curves for the inversion mode. For theA←Xsystem the experimental data is fitted by an expression:

ISSN:0026-8976    

DOI:10.1080/00268977000101541

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The 9-phenyl thiaxanthyl radical has been obtained from the corresponding cation. A complete analysis of its E.S.R. spectrum has been achieved by using some deuterated derivatives as well as computer simulated spectra. The unusual ratio of the ortho/para hyperfine splittings (✠) has been interpreted as due to the occurrence of restricted rotation of the phenyl ring. Molecular orbital calculations indicate that the experimental results may be interpreted by assuming the phenyl ring to be twisted from the heterocyclic plane by an angle of about 72°. No significant differences were observed between the values of the spin density distribution calculated with standardpanddmodels.

ISSN:0026-8976    

DOI:10.1080/00268977000101551

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A new direct difference method for the computation of molecular interactions has been based on a bivariational transcorrelated treatment, together with special methods for the balancing of other errors. It appears that these new features can give a strong reduction in the error of the interaction energy, and they seem to be particularly suitable for computations in the important region near the minimum energy.

ISSN:0026-8976    

DOI:10.1080/00268977000101561

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor