摘要:

In the present paper the pseudo Jahn-Teller interaction between the four lower electronic states of benzene is considered, with special reference to the mixing of the3B1uand3E1ustates through thee2gcarbon-carbon stretching mode. First a review is given of the pioneering work of Liehr on the static problem, where the ‘electronic Hamiltonian’ is solved as a function of fixed nuclear coordinates. Results of a specific calculation are presented.

ISSN:0026-8976    

DOI:10.1080/00268976700101151

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Measurements of the proton spin-lattice relaxation times have been made as a function of concentration and temperature in aqueous solutions of7LiCl and6LiCl. The difference in the relaxation times for two isotopic solutions of the same concentration and temperature is small, corresponding to a difference n reciprocal relaxation times of 0·004 sec-1.cat 25°c, wherecis the molarity of the solutions. This value decreases with increasing temperature. It is shown that the difference in relaxation times arises solely from the magnetic dipole interaction between the7Li ion nucleus and water protons. The concept of a long-lived, rigid hydrated complex around the Li ion is shown to be inconsistent with the results.

ISSN:0026-8976    

DOI:10.1080/00268976700101161

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The second moments of19F nuclear magnetic resonance lines of CF4and SF6in their respective clathrate hydrates indicate that these molecules are but little restricted by the walls of the clathrate cavities, and re-orient freely about chosen axes of symmetry at low temperatures and randomly at high temperatures. Above 150°k, we infer from our results that there occurs a limited isotropic translation, or ‘rattling’ movement of an SF6guest molecule up to a distance of about 0·5åfrom the centre of the clathration volume.

ISSN:0026-8976    

DOI:10.1080/00268976700101171

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A re-examination of the N.M.R. spectrum of mercury dimethyl using heteronuclear double resonance techniques confirms the values of the directly bonded andgeminalcoupling constants obtained by McLauchlanet al.[4]. The use of a locked oscillator system enables the signs and magnitudes of thevicinaland long-range coupling constants to be determined. The values obtained are3J13C--H= -1·9±0·2 c/s and4JH---H= +0·45±0·02 c/s respectively. The chemical shifts of the13C and199Hg resonances relative to T.M.S. are also given.

ISSN:0026-8976    

DOI:10.1080/00268976700101181

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

An N.M.R. study of AlCl3, TiCl4and paramagnetic CoCl2in water and in aqueous mixtures of acetone, acetonitrile, dimethylacetamide, N,N-dimethylformamide, dimethylsulphoxide, dioxane, ethanol, methanol, N-methylformamide, tetrahydrofuran, and tetramethylurea over a solvent range has been completed. The chemical shift results indicate that although water solvates ions extensively in all the mixtures, many of the organic components, particularly DMSO and the amides, compete effectively with water for added electrolyte. The diamagnetic and the paramagnetic solution results indicate that solvating ability decreases in the order DMSO > alcohols, amides > TMU, THF > acetone, acetonitrile, dioxane. This order correlates well with the basicities of these compounds but not with their dipole moments or dielectric constants.

ISSN:0026-8976    

DOI:10.1080/00268976700101191

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The14N chemical shifts in some thioamides have been measured using double irradiation techniques whilst observing the proton spectra of the compounds. These values are compared with those of the corresponding amides and the results support the proposal that the variation in14N chemical shifts within the amide range is governed by the degree of delocalization of the nitrogen lone pair of electrons. The14N chemical shift of one selenium derivative, selenobenzamide, has also been determined.

ISSN:0026-8976    

DOI:10.1080/00268976700101201

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

It is shown how the composite particle technique, which has proved useful for the analysis of the spectra of molecules in the isotropic liquid phase, may also be applied, with slight modifications, to spectra observed in an anisotropic environment. As an example, the analysis of the spectrum of ethyl iodide in the nematic phase is described.

ISSN:0026-8976    

DOI:10.1080/00268976700101211

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

This paper reports the results of an x-ray analysis, electron spin resonance, electrical conductivity,u.v.and visible spectroscopic measurements on TMPD-chloranil. The results can be explained by assuming a molionic lattice, i.e. a crystal lattice built up of neutral TMPD and chloranil molecules together with bi-valent positive TMPD ions and bi-valent negative chloranil ions. Elementary excitations creating (chloranil-… TMPD++… chloranil-) are presumed to be responsible for the measured paramagnetism.

ISSN:0026-8976    

DOI:10.1080/00268976700101221

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976700101231

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976700101241

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor