摘要:

A phenomenological analysis of the polyene optical excitation spectra is presented. The successive absorption bands are interpreted in terms of odd and even exciton levels. An extrapolation of the experimental data on the whole polyene series gives the exciton levels of an infinite chain, and the energy gap between the filled bonding band and the empty antibonding band. The dependence of the absorption frequencies on the length of the chain allows for a calculation of the effective masses for these bands; they turn out to be small, which implies that the degree of alternation between the simple and double bonds is weak.

ISSN:0026-8976    

DOI:10.1080/00268976700100791

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Further measurements of the nuclear electron Overhauser effect in solutions are reported for fluorine and protons. The proton-electron interaction is predominantly dipolar and the results are satisfactorily interpreted in terms of a model of randomly diffusing spheres. Fluorine-electron interactions, however, involve a scalar contribution, and current theories for the time dependence of this interaction give qualitative but not quantitative agreement with experiment. The effect of stimulated emission on the observed enhancements is discussed and concluded to be small in these experiments.

ISSN:0026-8976    

DOI:10.1080/00268976700100801

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The semi-phenomenological density matrix theory of Alexander [1] is applied to electron spin relaxation and then developed to encompass systems that show a large second-order hyperfine interaction. The equations of relaxation due to site-jumping are constructed and solved. It is shown that in the case of a static model the second-order spectrum reduces to the form calculated by Fessenden [2] for the case when the nuclei are equivalent. When the nuclei are brought to equivalence by a rapid motion then the spectrum shows a second-order splitting characteristic of the mean hyperfine splitting of the nuclei concerned, and not a spectrum which is the mean of the second-order splittings in the static case. The spectrum of PF4is then accounted for on an inversion model, but one that makes all nuclei equivalent in a correlated manner, and not in the pairwise-correlated manner previously suggested [3].

ISSN:0026-8976    

DOI:10.1080/00268976700100811

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The yield of the second species is about ten times that of the first.

ISSN:0026-8976    

DOI:10.1080/00268976700100821

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Two uses of13C satellites inXspectra ofXnAA′Xn′spin systems are discussed: (a) the derivation, from their fine structure, of coupling constant information unobtainable from the spectrum of the parent compound, and (b) their employment in heteronuclear double resonance experiments. The magnitudes of coupling constants to13C and the relative signs of these and other coupling constants are obtained for tetramethyldiphosphine.

ISSN:0026-8976    

DOI:10.1080/00268976700100831

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The electron spin coupling constants for thea,3A″state of H2CO have been calculated using a semi-empirical electronic wavefunction, and are in reasonable agreement with experiment. The low value of the spin-spin interaction constants is ascribed to a strong polarization of theπ*(b1-a′) molecular orbital in this state.

ISSN:0026-8976    

DOI:10.1080/00268976700100841

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Proton and fluorine resonance spectra of meta-difluorobenzene have been obtained under high resolution using a Varian spectrometer operating at 100 Mc/s and 94.1 Mc/s respectively. These have been analysed by treating the molecule as a six-spin system of the typeAB2MX2withC2vsymmetry. The secular equation is solved using IBM 1620 and 7044 computers. The chemical shifts and coupling constants are reported.

ISSN:0026-8976    

DOI:10.1080/00268976700100851

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Semi empirical calculations of proton hyperfine coupling constants in the allyl radical have made possible an assignment of splitting constants for the methylene protons.

ISSN:0026-8976    

DOI:10.1080/00268976700100861

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976700100871

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976700100881

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor