摘要:

The Kubo and Tomita formalism for the calculation of magnetic resonance absorption line shapes is generalized to include the effect of interdependent motional terms on a relaxing perturbation. When the perturbation is expressed in irreducible spherical tensor notation the second moments, relaxation times and line-shifts for a wide variety of interactions may be evaluated. The relevant properties of the tensors are determined and explicit calculations are performed. Results for typical interactions for electrons and nuclei are tabulated.

ISSN:0026-8976    

DOI:10.1080/00268976700101031

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

In order to demonstrate the predicted partial recovery of spin-spin coupling resulting when very high double irradiation fields are used, an AMX system (the vinyl group of vinyl acetate) was studied usingH2powers of up to 100 c/s. Optimum decoupling of the low field proton from the rest of the spectrum occurred when anH2power of 44 c/s was used. For powers >44 c/s the predicted increase in splittings was observed, the spectrum becoming more complicated as theH2power was increased. A good theoretical fit of the observed spectra was obtained using simple double resonance theory (without considering relaxation effects) although the values ofH2power used were by no means negligible compared with the chemical shifts involved. Various necessary corrections which must be applied in this type of experiment, in particular those due to shifts analogous to the Bloch-Siegert shift, are discussed. It is emphasized that in general, these effects may lead to complications when spin-decoupling experiments are carried out in order to simplify observed spectra.

ISSN:0026-8976    

DOI:10.1080/00268976700101041

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The Pariser-Parr-Pople type calculations are carried out for some aminosubstituted purines (6-amino, 2,6-diamino and 2,6,8-triaminopurine) and their parent molecule purine. The electronic spectra of these molecules are discussed. The calculated singlet-singlet (π→π* type) transition energies are in good agreement with the experimental data.

ISSN:0026-8976    

DOI:10.1080/00268976700101051

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

P-method calculations have been carried out on two non-planar dioxins to study the applicability of the method to such systems. The E.S.R. spectra have also been calculated using standard techniques for open-shell systems to test further the π-electron separability theorems.

ISSN:0026-8976    

DOI:10.1080/00268976700101061

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

E.S.R. measurements on the photodissociation-products of tetraphenyl-hydrazine in rigid solution at 77°Kindicate that the principal product of this dissociation is the dimer of the diphenyl amino radical. This assignment is confirmed by a measurement of a half-field signal and computer simulation of the E.S.R. spectra in rigid solution. A long wavelength charge-transfer band arises through the interaction of the two diphenyl amino radicals. An SCMO calculation is presented, which gives a theoretical background to the latter assignment.

ISSN:0026-8976    

DOI:10.1080/00268976700101071

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The proton spin-lattice relaxation time,T1, has been measured for a series of mixtures of bromobenzene in perdeuterobromobenzene and for 1,3,5 trideuterobenzene in perdeuterobenzene over the liquid range. The inter and intramolecular contributions to the relaxation have been separated. For bromobenzene both contributions vary in the same way with temperature and are thought to be due entirely to nuclear magnetic dipole interactions. This seems to indicate that the re-orientational and translational molecular motions are connected.

ISSN:0026-8976    

DOI:10.1080/00268976700101081

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Assuming a planar geometry ofCssymmetry and using a Urey-Bradley potential field, the force constants of dinitrogen trioxide have been re-determined within the formalism of Wilson'sG-Fmatrix method. The outcome of the present investigation suggests a new set of force constants some of which are drastically (∼ 50 per cent) different than those previously reported. Furthermore, since thei.r.frequencies used in the present investigation were obtained both in the solid state and at low temperatures, the mean amplitudes of thermal vibrations of both14N2O3and15N2O3are given at 77°k. Finally, it is suggested that more isotopici.r.data is necessary to ascertain unequivocably the geometry of dinitrogen trioxide.

ISSN:0026-8976    

DOI:10.1080/00268976700101091

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The treatment of Karplus for the pi-electron contribution to proton-proton coupling constants is extended in this paper to conjugated systems. The equation derived is applied tos-transands-cis1,3-butadienes, and the coupling constants obtained are compared with the experimental values. It is concluded that the five bond coupling constants5Jtcand5Jcc(the subscripts c and t refer to thecisortransorientation of the bonds of the coupling path—see Part I) in thes-transmolecule are due to a pi mechanism, and that for cyclohexadiene the five bond coupling constant has a large contribution from this effect. The results for the four bond couplings are less conclusive, but it is suggested that a pi mechanism is dominant ins-transdienes, whereas a sigma mechanism dominates for cyclohexadiene.

ISSN:0026-8976    

DOI:10.1080/00268976700101101

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976700101111

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976700101121

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor