摘要:

An expression is given which fairly accurately provides valence-state energies. It is shown that one can formally attribute the meaning of the one-centre integrals to the coefficients in such an expression. In this way one also obtains the criteria of Pariser and Parr. Moreover, if one introduces such semi-empirical integrals in the expression which gives the vertical ionization potentials and electron affinities, one obtains the corresponding experimental values. On the basis of these facts usage of such semi-empirical integrals in the M.O.-L.C.A.O. theory is proposed. A discussion of the advantages and the limitations of its application is made.

ISSN:0026-8976    

DOI:10.1080/00268976600100161

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

An S.C.F.-M.O.-L.C.A.O. calculation in the Roothaan-Popie scheme, using the Pariser-Parr approximations, has been carried out for the ions [CrO4]--and [MnO4]-.

ISSN:0026-8976    

DOI:10.1080/00268976600100171

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The1H,199Hg and13C spectra of the more common of the isotopic species occurring in natural abundance in mercury dimethyl have been studied. The proton spectra were observed directly whilst the199Hg and13C spectra were measured indirectly by a double resonance method involving observation in the proton region. A hitherto unreported long range coupling of magnitude 0·44±0·02 c/s was observed between the methyl protons and new values were obtained for the directly bonded13C-H coupling, ± 129·6±0·1 c/s, and for the geminal199Hg-12C-H coupling, ± 101·9±0·1 c/s. The relative signs of these couplings, together with the sign and magnitude of the directly bonded199Hg-13C coupling, ±689±2 c/s, were determined by experiments on the 0·33 per cent abundant species H313C199Hg-12CH3. The magnitude of the199Hg-13C coupling is discussed in terms of the correlation between reduced coupling constants and atomic number. The vicinal13C-Hg-12CH3coupling appears to be zero.

ISSN:0026-8976    

DOI:10.1080/00268976600100181

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Measurements of the spin-lattice relaxation time,T1, for the75As nucleus are presented for solutions of potassium hexafluoroarsenate in acetonitrile, acetone, ethyleneglycol-dimethylether and diethyleneglycol-dimethylether. Viscosity and density data are given for each series of solutions. Plots of (T1)-1against viscosity are linear for each solution. The relaxation is interpreted in terms of the fluctuating quadrupole coupling of the75As nucleus, the mean square value of which is constant over the whole concentration range for a given solvent. Possible origins of the electric field gradients at the75As nucleus are discussed in the light of this and earlier work on similar systems. The viscosity and density data are used to obtain a set of ‘ solvation numbers ’.

ISSN:0026-8976    

DOI:10.1080/00268976600100191

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The proton spin-lattice relaxation time,T1, has been measured for a series of mixtures of benzene in perdeuterobenzene for the liquid in equilibrium with its vapour over the temperature range from below the normal freezing point up to the critical temperature. The two contributions toT1due to interactions within the molecule (T1 intra) and between molecules (T1 inter) have been separated and are found to be very different in magnitude and in variation with temperature. The variation and magnitude ofT1 intercorrelates well with other translational motion dependent properties such as self diffusion and viscosity. The correlation ofT1 intrawith other re-orientation dependent properties such as deuteronT1and Rayleigh scattering is poor.

ISSN:0026-8976    

DOI:10.1080/00268976600100201

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

A method is described for calculating low resolution differential cross sections near the rainbow angle. It is used to calculate a table of the positions of the principal maxima and minima in the rainbow structure for a 6–12 potential for different rainbow angles and different values of the de Boer parameter, Λ*, between 0·1 and 0·01. A comparison with similar results obtained using Ford and Wheeler's approximation shows that the latter is quite accurate for determining the energy parameter, ε, but is usually unsatisfactory for determining the distance parameter, σ. A method is given for determining both of these parameters more accurately from the values in the table and a further table is given with which it is possible to determine which region of the real potential is being fitted by the 6–12 potential. It is found that the rainbow structure in determined only by the attractive part of the potential close to the minimum and is independent of the shape of the potential inside the minimum.

ISSN:0026-8976    

DOI:10.1080/00268976600100211

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

A semi-empirical calculation of the orbital energy levels of CuF6-4has been performed using the Wolfsberg-Helmholz approximations as extended by Ballhausen and Gray. The calculated value of 10Dqis rather insensitive to the initial assumptions and is in good agreement with experiments. The location of the ‘non-bonding’t1ulevel is on the other hand found to be very dependent upon the atomic wavefunctions used.

ISSN:0026-8976    

DOI:10.1080/00268976600100221

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Using the LCAO-MO wavefunctions estimated by an extended Wolfsberg-Helmholz method, the first order static Jahn-Teller effect in CuF6-4has been calculated. The bond length difference between the long and the short bonds is found to be some 0·2å, in reasonable agreement with experiment.

ISSN:0026-8976    

DOI:10.1080/00268976600100231

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

More accurate equations than previously used to describe a non-perfect spherical reference system are given, and experiments to confirm them described. When such a system is used to measure chemical shifts, there should be a correction due to the magnetic susceptibility of the material from which the sphere is made, as well as corrections due to the susceptibilities of the solutions. It is also shown that the change in magnetic field strength, caused by insertion of a sample into the pole gap of a magnet, may be significant in certain circumstances. The ‘substitution’ method of external referencing must therefore be used with care.

ISSN:0026-8976    

DOI:10.1080/00268976600100241

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976600100251

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor