摘要:

A model of unimolecular reactions allowing for the possibility of an energy exchange between the vibrational degrees of freedom is investigated for the case of a rapid energy exchange between a limited number of modes of vibrations with linearly independent frequencies.

ISSN:0026-8976    

DOI:10.1080/00268976700100131

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Šolc's result, for the average of the unimolecular rate constant over redistributions of energy between some of the oscillators, is obtained by a ‘statistical’ argument.

ISSN:0026-8976    

DOI:10.1080/00268976700100141

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A nuclear magnetic resonance rate study of complexes of N,N-dimethylformamide (DMF) with AlCl3, BeCl2, GaCl3, SbCl5and TiCl4has been carried out. Measurements were made possible by the observation of separate resonance signals for bulk and complexed DMF in all solutions. Rate constants at 290°kvaried from 2 sec-1for the AlCl3. (DMF)nsystem to about 150 for the BeCl2. (DMF)nsolution. Activation energies for the exchange process were also measured for all solutions.

ISSN:0026-8976    

DOI:10.1080/00268976700100151

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

H1magnetic resonance absorption in (NH4)3ZrF7has been studied over the temperature range 20° to -196°c. A line width transition due to low activation energy reorientations of two types of NH4+ion was observed. The fluorine absorption data give also evidence of reorientation of zirconiumfluorine complex. The transient experiment carried out at 15·3 and 22·9 Mc/sec in the same temperature interval supports the absorption results by indicating conclusively that two motions are effective in the crystal studied. The slower one is the zirconium-fluorine ion reorientation, the faster one, the reorientation of the weakly hydrogen-bonded NH4+ions. The relaxation data exhibit strong F-H and H-F cross relaxations: at higher temperatures fluorines and protons relax essentially through the slower motion of the zirconium-fluorine complex, while at lower temperatures both spins relax through the high frequency reorientation of the NH4+ions. The observed dynamic disorder is compatible with the Hampson-Pauling interpretation of the (NH4)3ZrF7structure and thus supports implicitly the existence of the (ZrF7)---complex.

ISSN:0026-8976    

DOI:10.1080/00268976700100161

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The line-widths of an AB spectrum are calculated on the assumption that the relaxation is caused by a paramagnetic ion or radical interacting with the nuclei by both scalar and dipolar perturbations. The bases of the interaction mechanism are the ‘sticking’ and ‘diffusion’ models of Hubbard [3]: these models enable the line-width variation of the spectrum to be calculated explicitly and compared with results obtained for two AB systems containing tri-tert-butyl phenoxy radical.

ISSN:0026-8976    

DOI:10.1080/00268976700100171

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Expressions are derived for the correlation functions and relaxation times for electron-spin relaxation caused by a modulated interaction with the molecular rotation. A tensorial interaction is assumed and the molecule is not necessarily taken to be a spherical top. The paper is in some respects an extension of that by Hubbard [1] for nuclear spin-rotation relaxation.

ISSN:0026-8976    

DOI:10.1080/00268976700100181

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The force constants of the general valence force field (G.V.F.F.) are calculated with a new method (‘Verfahren der nächsten Lösung’) for all molecules and ions, for which frequency data are available in the literature (XeF4, JCl4-, PtCl42-, AuCl4-, AuBr4-and (Pt(NH3)4)2+).

ISSN:0026-8976    

DOI:10.1080/00268976700100191

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Electron spin resonance spectra were obtained of the 3-nitropyridine, 3,5-dinitropyridine, 2-chloro-5-nitropyridine, 5-nitropyrimidine, 3-acetyl pyridine anion radicals produced electrolytically in dimethyl-sulphoxide solutions. Hyperfine splitting constants were assigned in some cases with the help of molecular orbital calculations. The 3-acetylpyridine anion exists in two isomeric forms, the spectra of which were observed. Ionization of chloride from 2-chloro-5-nitropyridine, 2-chloro-3-nitropyridine, and 2-chloro-5-nitropyrimidine occurred on reduction, yielding the 3-nitropyridine anion from the first two compounds, and the 5-nitropyrimidine anion from the third. Analysis of the data suggests that, for this series of radicals, theσ-πparameter Qcnnis in the range 0 ⩾ Qcnn⩾ -2·5 gauss.

ISSN:0026-8976    

DOI:10.1080/00268976700100201

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The radical CH3CHCOOH has been identified by ENDOR measurements as a minor product of the irradiation of succinic acid with x-rays at room temperature. The rotating methyl group gives fairly sharp ENDOR transitions which show second-order splitting. The relative intensities of the transitions suggest a strong relaxation mechanism associated with a time dependent scalar coupling.

ISSN:0026-8976    

DOI:10.1080/00268976700100211

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The origin of the quadrupole splittings observed in the Mössbauer spectra of the normal spinels ZnFe2O4and CdFe2O4has been investigated using a point charge model. The magnitude of the electric field gradient at the octahedral sites is very sensitive to the value ofu, the distortion parameter of the anion sub-lattice. Induced dipole moments on the O2-ions have a substantial effect on the magnitude of the quadrupole splitting. The calculations, combined with the experimental results, are used to deduce information about the relative amounts of distortion in the two compounds.

ISSN:0026-8976    

DOI:10.1080/00268976700100221

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor