摘要:

A new method is described for calculating high-order interaction energies of a pair of atoms separated by large distancesR. It is applied to a pair of ground-state hydrogen atoms with the result that the leading term of the third-order interaction energy is -3986/R11in atomic units.

ISSN:0026-8976    

DOI:10.1080/00268976800100101

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A high-resolution N.M.R. study of 3,3,3-trifluoropropyne in different liquid crystals is reported. The relative geometry obtained agrees with microwave data. The sign ofJ(HF)is negative. The anisotropies in fluorine and proton chemical shifts have been measured, and are comparable in magnitude and sign with values previously reported for similar compounds.

ISSN:0026-8976    

DOI:10.1080/00268976800100111

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A practical method is given for measuring inter-system crossing yields. It is applicable to triplets with lifetimes larger than 10-2s.

ISSN:0026-8976    

DOI:10.1080/00268976800100121

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

In molecular encounters, the total energy of the system may not be sufficient to enable any but the ground-state electronic surface to determine nuclear motionsadiabatically. When this happens, non-adiabatic transitions areenergetically forbidden.

ISSN:0026-8976    

DOI:10.1080/00268976800100131

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The origin of the broadening of the N.M.R. signal of the proton(s) in the α position to the nitrogen atom in nitrogen-containing heterocycles (pyridine, thiazole, isothiazole, isoxazole) is examined. The contributions of the various nuclear relaxation mechanisms to the spin-latticeT1and spin-spinT2relaxation times of Hαare considered. It is concluded that the observed broadening arises from incomplete washing out of an N-Hαspin-spin coupling by14N quadrupolar relaxation. The calculated line-broadenings agree well with the observed line-widths. The effect of temperature changes, solvents, protonation and quaternization is discussed in terms of the14N quadrupolar relaxation time. Various15N-H couplings over two or three bonds are reported.

ISSN:0026-8976    

DOI:10.1080/00268976800100141

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Qfactors have been calculated for fluorine hyperfine interaction inπ-electron radicals using an independent-electron model for theσorbitals. It is shown that the off-diagonal elements give an important contribution to fluorine coupling constants. Combining theseQfactors with calculatedπ-electron spin densities of fluoro-nitrobenzenes gives good agreement with experimental coupling constants.

ISSN:0026-8976    

DOI:10.1080/00268976800100151

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The energies of the Rydberg states of H2O relative to the ionization potential have been calculated starting from the energies of the Ne Rydberg states. The first step is the calculation of Ne valence state energies, the second is the calculation of first and second-order perturbations due to the change in the nuclear framework. These perturbation terms are sensitive to the form of the wave function of the Ne Rydberg orbitals. SCF wave functions have been chosen when available. There is a reasonable agreement between the calculated and observed energies except for the 3sstates which are probably better correlated with a transition to an anti-bonding molecular orbital than a transition to a Rydberg orbital.

ISSN:0026-8976    

DOI:10.1080/00268976800100161

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Displacement lattice vibration frequencies are calculated for a number of simple molecular crystals using a central force field approximation. The results are compared with experimental results. In the case of ammonia, where more experimental results are available, the calculation is extended to include electrostatic effects.

ISSN:0026-8976    

DOI:10.1080/00268976800100171

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The electron distribution of the F centre, in alkali halide crystals, is described using topological wavefunctions which reflect the nature of the immediate ionic environment surrounding the vacancy. Calculations of the transition energies for the optical absorptions are given. The dependence of the transition energies on the details of the electron distribution is examined theoretically.

ISSN:0026-8976    

DOI:10.1080/00268976800100181

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Sub-spectral, direct and perturbation techniques have been applied in the analysis of the N.M.R. spectrum of pyridine. The results are compared with those obtained by the iterative method. A close agreement between the two is found. The negative coupling constantJXX′ is confirmed directly by identification of the symmetry species of theabc-type sub-spectra by use of tickling. Limitations of the direct method of analysis are discussed.

ISSN:0026-8976    

DOI:10.1080/00268976800100191

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor