摘要:

An apparatus is described for measuring the magnetic circular dichroism spectra of matrix-isolated species over the temperature range 14–50 K. Results are presented illustrating the range of materials which can be investigated (from mercury atoms to phthalocyanine molecules). The detection of transitions in oxygen, which are extremely weak in absorption, clearly demonstrates the high sensitivity of magnetic circular dichroism measurements on paramagnetic species at low temperature.

ISSN:0026-8976    

DOI:10.1080/00268977400102661

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The Hartree-Fock perturbative approach to second-order properties is developed in terms of the uncoupled first-order density matrix. Apart from its theoretical interest, the present formulation is particularly suitable for computational purposes. The applications are to π-electron systems: a comparison with coupled results for dipole polarizabilities, magnetic susceptibilities and shielding is also given.

ISSN:0026-8976    

DOI:10.1080/00268977400102671

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Non-adiabatic calculations are reported for the two lowest non-rotational energy levels of H2+, HD+and D2+. They are lower in energy than previously published non-adiabatic calculations and the dissociation energies are 21 379·28, 21 515·99 and 21 711·51 cm-1for H2+, HD+and D2+, respectively. Certain approximate ratios for the non-adiabatic corrections are discussed and shown to be in reasonable agreement with the exact ratios. It is suggested that the Unsöld average-energy denominator for H2+should lie between 2·6 × 105and 3·6 × 105cm-1.

ISSN:0026-8976    

DOI:10.1080/00268977400102681

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Gas-phase E.P.R. spectra from the first six vibrational levels in X3Σ-SO have been detected and analysed using a Hund's case (b) formalism. The spectra can be fitted using the following molecular constants:

ISSN:0026-8976    

DOI:10.1080/00268977400102691

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A procedure is described for the calculation of spin-restricted single-determinant molecular orbital wavefunctions for systems such as free radical ground states and lowest triplet states. It is a further development of ‘partitioning techniques’, which divide the available one-electron space (for a given basis) into three mutually orthogonal subspaces for doubly-occupied, singly-occupied and empty orbitals respectively. Necessary and sufficient conditions are derived for the calculated total energy to be stationary with respect to changes in these subspaces. These lead to an iterative procedure for the determination of self-consistent molecular orbitals. Some preliminary applications to hydrocarbon radicals are described and compared with corresponding spin-unrestricted results.

ISSN:0026-8976    

DOI:10.1080/00268977400102701

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A formal partial wave analysis of the third-order energy for the interaction of three non-degenerate S-state atoms is used to identify those non-additive terms which, in the limit of negligible charge overlap between the interacting atoms, reduce to the usual long-range expanded form of the triple-dipole energy. Pseudo-state techniques are used to evaluate these terms, both with and without the inclusion of charge-overlap effects, over a range of interatomic separations and angles for the interaction of three ground-state hydrogen atoms. These results are used as a model to discuss the way in which charge-overlap effects modify the usual long-range result for the triple-dipole energy. In addition to the familiar modification of the radial dependence of the interaction energy, charge-overlap effects are found to give rise to a modification of the angular dependence; the latter effect has no analogue in two-atom interactions. The significance of these results is discussed briefly.

ISSN:0026-8976    

DOI:10.1080/00268977400102711

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The processes of the hybridization of atomic orbitals and the localization of molecular orbitals are treated in a unified manner through the introduction of a criterion of maximum or minimum projection. This is an extension of the maximum overlap approach to hybridization. It leads, first, to a proposal for a general index of the extent of hybridization or localization and, secondly, to a new method of finding hybrid atomic orbitals and localized molecular orbitals using projection techniques. Results are presented for the diatomic molecules Be2, HF and CO, and a comparison with previous methods is made.

ISSN:0026-8976    

DOI:10.1080/00268977400102721

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Single crystals of the cycloadduct of 1-(9-anthryl)-3-(1-naphthyl)propane (CANP) have been prepared, enabling a photochemical and photophysical study to be made of the anthracene-naphthalene sandwich pair in this material. The low temperature fluorescence spectrum is broad, exciplex in nature, and has a decay time of about 80 ns. This emission is quenched as the temperature is raised by a process which involves photocyloaddition of the pair. Arrhenius plots give an activation energy of about 600 cm-1for the photochemical process. The analogous photophysical properties have also been studied in methylcyclohexane glasses at 77 K and 60 K. Formation of the sandwich pairs at 77 K gives rise to a ‘ partially relaxed ’ pair having some structure in its emission spectrum and a shorter lifetime. Possible reasons for the differences in properties of sandwich pairs in methylcyclohexane glasses and the parent cycloadduct crystals are discussed. Very weak emission from the naphthalene moiety of monomer ANP has been observed at 77 K.

ISSN:0026-8976    

DOI:10.1080/00268977400102731

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Single crystals of the intermolecular photodimer of 1-(9-anthryl)-3-(1-naphthyl)propane have been prepared. The photophysical properties of this molecule as well as the sandwich dimer obtained by photocleavage in methylcyclohexane at 77 K have been recorded. A qualitative study of the photochemical properties of the sandwich dimer in single crystals of the photodimer host shows that the photochemical mechanism is similar to those of the anthracene sandwich pair and the anthracene-naphthalene pair.

ISSN:0026-8976    

DOI:10.1080/00268977400102741

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Various properties of the projection operators employed in the theory of fluids are examined with particular reference to those properties which are essential in the simplification of the equations of motion for reduced distribution functions. A natural consequence of these investigations is the deduction of such equations of motion for a number of different physical situations.

ISSN:0026-8976    

DOI:10.1080/00268977400102751

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor