摘要:

The electronic absorption and E.S.R. spectra of the benzene and 2,2-paracyclophane anions were measured. The paracyclophane anion showed a strong absorption band at 760 mμ and an E.S.R. pattern with hyperfine structures of 41 lines. On the other hand, the benzene anion had an absorption peak at 420 mμ and an S.E.R. spectrum with hyperfine structures of seven lines. Combining these experimental results with a molecular orbital calculation taking account of configuration interaction, we were led to the conclusion that there exists an electron resonance interaction between the π electron systems belonging to the two benzene rings of the paracyclophane anion and that the exchange interaction energy between them amounts to 0·82 ev. Furthermore, the 760 mμ band was interpreted to be a charge-(or electron) resonance absorption caused by the electron-resonance interaction. The π-electron structure of the biphenyl anion was also studied theoretically and the result was compared with that for the paracyclophane anion.

ISSN:0026-8976    

DOI:10.1080/00268976700100011

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A method is indicated whereby the quadrupole splitting arising from the d-electrons and the contribution from the crystalline matrix can be determined from the experimental Mössbauer spectra. The general temperature dependence of the quadrupole splitting of the low spin ferric compounds is first calculated from the experimentalg-tensor and then for the case when the iron atom is in a strong crystal field of tetragonal symmetry. Covalency effects are also considered. The parametere2Q'r-3> is determined as 8·9 mm/sec which not only suggests screening effects in these complexes but enables an estimate of the degree of bonding of the iron with the ligands.

ISSN:0026-8976    

DOI:10.1080/00268976700100021

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Equations are derived which describe the E.S.R. spectra of free radicals in solution when the spin exchange interactionJS1.S2provides the dominant relaxation mechanism. It is shown that modified Bloch equations provide an adequate description ifJis much greater than any frequency differences in the spectrum and the hyperfine interactions can be neglected during spin exchange collisions, but that in general the exchange rate depends on the frequency differences and spin de-phasing effects can occur even in the absence of spin exchange. Also, small shifts in resonance frequencies are shown to arise because of electron spin polarization in the applied field; but these are usually much smaller than the line widths.

ISSN:0026-8976    

DOI:10.1080/00268976700100031

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The spectral inertness of the -NH3+group is examined using a potential which has both short- and long-range characteristics. The positively charged nitrogen dominates the potential, although to obtain a satisfactory description account must be taken of the repulsion arising from overlap of substituent and ring orbitals. The substituent parameters for the potential are estimated. Using perturbation theory the shifts of bands associated with a re-arrangement of charge within the molecule are calculated assuming that only the inductive effect of the substituent is important. Finally the potential used in this paper is compared to that of Bishop and Craig [4].

ISSN:0026-8976    

DOI:10.1080/00268976700100041

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The shift ofn-π* bands of some azines on chloro substitution is examined assuming that the chloro substituent has only inductive character. This inductive character consists of both σ and π-electron interactions; the σ effect is approximated by the theory of Pople and Santry [7], whilst the π effect is assumed to have both short and long-range characteristics in the perturbing potential [1]. The calculations lead us to the conclusion that the approximations made in the estimation of σ effects are almost certainly responsible for the poor agreement observed between theory and experiment.

ISSN:0026-8976    

DOI:10.1080/00268976700100051

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A general expression is derived for the isotropic proton hyperfine interaction constant arising from spin density at the carbon C′ in anncarbon aliphatic chain fragment C′-Cn-H due to spin polarization. The experimental results are then discussed for the proton hyperfine interaction constants in a series of substituted naphthalene negative ions and alkyl iron(III) dithiocarbamates.

ISSN:0026-8976    

DOI:10.1080/00268976700100061

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A conductivity cell of the thick-wire variety of the hot-wire type has been employed to measure the thermal conductivity of the binary and ternary systems: He-Ne, He-Xe, Ne-Xe and He-Ne-Xe. The values are reported in each case as a function of composition at 30, 50, 70 and 90°c. These results are interpreted on the basis of the rigorous Chapman-Enskog kinetic theory using the well-known modified Buckingham exponential-six potential. Some commonly employed approximate, empirical semi-empirical procedures of computing the thermal conductivity of gas mixtures are also discussed and critically examined on the basis of these data.

ISSN:0026-8976    

DOI:10.1080/00268976700100071

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A general theory is presented for relaxation in solution electron resonance resulting from spin-rotational interaction. This is then applied to organic free radicals as well as doublet transition metal ions, and is further extended to cover multiplicities greater than two. Numerous experimental results are thereby given a unified interpretation.

ISSN:0026-8976    

DOI:10.1080/00268976700100081

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

An approximate self-consistent field method is described for calculating valence shell excitation energies and molecular structures. This uses many of the simplifications of calculations based on the neglect of differential overlap, but is extended by the use of atomic orbital exchange integrals to resolve open-shell configurational degeneracies in all cases (an exchange modified zero differential overlap method, EMZDO). The accuracy of this method is tested by application to CH, OH, CH2, NH2, H2O, NH3and H2CO, with encouraging results in most cases.

ISSN:0026-8976    

DOI:10.1080/00268976700100091

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976700100101

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor