摘要:

The electronic structure of the ethylene molecule is rescrutinized within the framework of the semi-empirical pi-electron theory. The lower electronic energy levels, twisting frequency, ionization potential and electron affinity are calculated without treating the so-called β parameter as empirical. A new approach for calculating the ionization potential is presented, in which an allowance is made for the change in the effective nuclear charge accompanying the actual ionization. The ionization potential is computed to be 10·757 ev, the observed value being 10·62 ev.

ISSN:0026-8976    

DOI:10.1080/00268976000100551

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Calculations on the lower electronic states, ionization potential and electron affinity of ethylene are carried out by a semi-empirical ASMO method including configuration interaction. The carbon-carbon sigma bonding electrons are explicitly included. One-centre quantities for ethylene, ethylene negative ion and ethylene positive ion are evaluated from atomic valence-state energies, taking account of changes in effective nuclear charges of the corresponding states. Two-centre electronic repulsion integrals are determined by interpolation between theoretical values for distant nuclear separations and one-centre repulsion integrals obtained; two-centre core integrals are computed purely theoretically. Good agreement between calculated and observed values is obtained. Although preferential stabilization of the ion cannot be expected from sigma-pi configuration interaction, it is shown that the reorganization of the electronic sub-structure of the atom upon ionization plays a significant role.

ISSN:0026-8976    

DOI:10.1080/00268976000100561

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

On the basis of a qualitative quantum mechanical theory of the energies and dipole strengths of the lower π-electronic transitions in alternant hydrocarbon molecules and their mono- and di-valent ions a comparison is made between the spectra in the 5–45 kK region of the molecules and ions of naphthalene, anthracene, tetracene, pyrene and perylene.

ISSN:0026-8976    

DOI:10.1080/00268976000100571

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

A general theory is presented of the high-resolution nuclear magnetic resonance spectra of systems in which two nuclei have a relative chemical shift comparable with their spin-coupling constant, all other relative chemical shifts being large. In the conventional notation such systems may be described as ABRpXq…, wherep,q… are small integers. All such systems can be handled within one theoretical scheme and the spectra, although possibly containing many lines, can be built up as the superposition of spectra of simpler types. The theory is illustrated by the analysis of the proton resonance spectrum of trans-crotonaldehyde which, in suitable solvents, is an example of ABR3X.

ISSN:0026-8976    

DOI:10.1080/00268976000100581

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The theoretical scheme described in Part I for the analysis of nuclear resonance spectra of the type ABXqis extended to systems AB2Xqwhere the symmetry is such that there is only one BX coupling constant. It is shown that these spectra can be interpreted in a systematic manner for allq. The spectra allow determination of the relative signs of all three coupling constants and can therefore be used to compare couplings between nuclei of different species (AX and BX) with the coupling between nuclei of the same species (AB). Further systems which could be studied by similar methods are indicated briefly.

ISSN:0026-8976    

DOI:10.1080/00268976000100591

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

By assuming an interaction energy for krypton and xenon of the same shape as that established for argon in an earlier paper and without introducing any adjustable parameters, values of the equilibrium properties of the crystals have been calculated which agree with the measured values to within the experimental accuracy or to within one per cent.

ISSN:0026-8976    

DOI:10.1080/00268976000100601

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Using the interaction energy between argon atoms deduced in a previous paper from the properties of the crystal and the gas and regarding the liquid as an approximately equimolar mixture of structures with coordination numbersz= 12 andz= 8 we have calculated the total energy of the liquid at the triple point in good agreement with experiment.

ISSN:0026-8976    

DOI:10.1080/00268976000100611

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The barrier to rotation in ethane is discussed in terms of hydrogen-hydrogen exchange integrals properly weighted by experimentally determined bond orders. Such bond orders are proportional to the spin correlation of delocalized electrons as determined from nuclear magnetic resonance spin-spin coupling constants. The calculated value of 2·3 kcal per mole determined for the rotational barrier in ethane in this study is in good agreement with the experimentally determined value of 2·7–3·0 kcal per mole.

ISSN:0026-8976    

DOI:10.1080/00268976000100621

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The signs of the chemical shifts of the proton resonance frequencies in paramagnetic metallocenes are discussed.

ISSN:0026-8976    

DOI:10.1080/00268976000100631

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The transfer of vibrational energy from molecules ofβ-naphthylamine excited by the mercury lines at 2804 Å and 2652 Å to the homologous series of paraffin hydrocarbons up ton-hexane has been investigated in the gas phase at 180°C. Although the average amount of energy transferred collisionally increases with the complexity of the added gas by a factor of 5, the transfer efficiency expressed as an accommodation coefficient remains virtually unchanged.

ISSN:0026-8976    

DOI:10.1080/00268976000100641

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor