摘要:

La chaleur spécifique du tétraméthyl-2,2,6,6 pipéridinol-4 oxyle-1 a été mesurée de 1,3°kà 74°k.

ISSN:0026-8976    

DOI:10.1080/00268976800100221

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Irradiation with a weak perturbing field can be used to locate precisely hidden13CH satellite lines in a proton magnetic resonance spectrum, and hence to determine C-C-H coupling constants. The technique is primarily applicable to two or three-spin systems, but, by combination with spin-decoupling, is extended here to the more complex spin system found in allyl bromide.

ISSN:0026-8976    

DOI:10.1080/00268976800100231

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A high resolution E.S.R. spectrum of the 2,4,6-triphenylpyryl radical is presented. By investigating some deuterium substituted derivatives and with the help of simulated spectra, all hyperfine coupling constants were derived. Also an attempt to rationalize the electron-proton coupling constants in terms of twisting angles of the phenyl rings out of the heterocyclic plane was made.

ISSN:0026-8976    

DOI:10.1080/00268976800100241

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Calculations have been made of the influence of the number of valence-shell electrons of a sulphur atom on the binding energies of 1sand 2pelectrons. These energies are related to the chemical shift of the Kαline and of the absorption edge as measured by electron spectroscopy. The present calculations extend previous work by using the full self-consistent-field technique and by considering both the parent and daughter systems. In so far as the flow of charge in a chemical bond may be related to the effective (fractional) number of valence electrons, this shows that information about the degree of ionic character can be obtained from accurate experimental observation of these phenomena. Estimates are made for sulphides, sulphites, and sulphates. For the full application of the method very high experimental precision is necessary.

ISSN:0026-8976    

DOI:10.1080/00268976800100251

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The relative intensities of thed-dbands in the visible spectrum of the tetrachloroferrate(III) ion have been calculated in a semi-empirical MO model in which it has been assumed that all intensity of the spin-forbidden bands has been borrowed from the two lowest-energy charge-transfer bands via direct spin-orbit coupling of the charge-transfer upper states and the metal4Γ states. The prominence of the4E(4D) band is reproduced especially well in the calculations. A comparison of the intensity of this band and the first charge-transfer band gives a rather realistic value for the π-antibonding MO eigen vector. The observed intensities of the ions FeCl4-and FeBr4-could also be related in a satisfactory way.

ISSN:0026-8976    

DOI:10.1080/00268976800100261

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A general discussion is given of the problems of assigning changes in nuclear spin relaxation rates, brought about by changes in system composition, temperature, etc., to changes in correlation times and/or nucleus-lattice coupling energies. In particular the usually assumed proportionality of correlation time and viscosity is examined in detail for aqueous electrolyte solutions. It is concluded that for ions which have a marked effect on the ‘structural equilibrium’ of the water, the correlation time—viscosity proportionality is unlikely to exist. It is suggested that in favourable cases individual particle self-diffusion coefficients are likely to be related in a simple way to correlation times. This is supported by available results for aqueous potassium iodide solution.

ISSN:0026-8976    

DOI:10.1080/00268976800100271

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Measurements of the spin-lattice relaxation times,T1, for the75As nucleus are presented for solutions of potassium hexafluoroarsenate in diethyleneglycol dimethylether (diglyme) over the temperature range 306·7–363·2°k. Values ofT1are also given for solutions of the silver and tetra-n-butylammonium salts in acetonitrile and acetone respectively, at 293·2°ktogether with values for solutions of various mixtures of salts. Density and viscosity data are given for each solution. The slopes of (T1)-1against viscosity/temperature graphs are found to be independent of solution composition for a given salt and solvent but are functions of temperature and cation. Solvation data, calculated from the viscosity and density measurements, together with the effects of cation and temperature on the relaxation rates indicate that relaxation is probably caused by cation-anion interactions. It is suggested that the relaxation is brought about by a short range interaction, which at any given instant is being experienced by an approximately concentration independent fraction of the arsenic nuclei.

ISSN:0026-8976    

DOI:10.1080/00268976800100281

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Studies of the nitrogen, deuteron and proton relaxation rates of liquid acetonitrile at various temperatures were carried out by pulsed N.M.R. techniques. Re-orientation of the methyl group about its symmetry axis is found to be approximately ten times faster than the re-orientation of the nitrile group. Analysis of the data provides an example of a large room-temperature contribution to the intramolecular relaxation component by a spin-rotation interaction. Previously sizeable spin-rotation interactions were considered to be insignificant for organic molecules at room temperature.

ISSN:0026-8976    

DOI:10.1080/00268976800100291

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Oscillator strengths for ethylene and benzene are calculated from transition gradients in the molecular orbital approximation with zero differential overlap. The results are much closer to the experimental values than the oscillator strengths calculated from transition moments. The effect of inclusion of overlap and other effects are also investigated.

ISSN:0026-8976    

DOI:10.1080/00268976800100301

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976800100311

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor