摘要:

In this review (containing 185 references) we discuss the vibration-rotational spectroscopy arising from one-photon electric-dipole moment transitions of diatomic molecules in the1∑ state. After a brief survey of the physical effects underlying the interaction of two atoms, we invoke the customary Born-Oppenheimer separation of electronic and nuclear motions in the molecule and introduce the concept of the potential-energy function. We discuss several model functions for the potential energy and their relationship to a general power-series representation, first treated by Dunham, that provides the framework for the analysis of accurate experimental data on transition frequencies. The WKB method of obtaining the term values of energy as functions of the Dunham potential-energy coefficients is described in detail and new results generated by computer algebra are presented. An analytic algorithm for obtaining the wavefunctions corresponding to the Dunham potential-energy function is reviewed and extended. One can use these wavefunctions to derive expressions for expectation values and matrix elements of powers of the reduced displacement from equilibrium; we also discuss several alternative methods, not involving the wavefunctions directly. The use of these matrix elements in the extraction of the dipole-moment function from experimental data on spectral intensities is illustrated by explicit calculations for HC1. In the final section we consider deviations from the Born-Oppenheimer approximation for both the potential-energy and dipole-moment functions, as well as other limitations of the Dunham formalism. Finally we mention briefly some recent trends and developments that we expect to become increasingly important as experimental sophistication advances.

ISSN:0144-235X    

DOI:10.1080/01442358309353338

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Starting with an historical account of the emergence of the Compton effect, the review summarizes the essential features of the processes involved in Compton scattering and outlines the theory required to interpret Compton profiles in terms of the momentum density, momentum wavefunctions and position wavefunctions. In this connection the essentials of the impulse approximation and the convenient concept of the reciprocal form factor are explained. Experimental procedures for the determination of Compton profiles using y-ray, X-ray and electron sources are briefly described and so also is positron annihilation. The advantages and insights afforded by Compton profile measurements in the study of electronic properties are illustrated by reference to a range of materials including elemental and several binary solids. Future prospects, especially in solid-state chemistry where Compton scattering could prove advantageous, are briefly outlined.

ISSN:0144-235X    

DOI:10.1080/01442358309353339

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A survey is given of simple predictive models and operational definitions of the metallic state. The purpose of this work is to highlight the essential features of electron localization versus itinerancy in both crystalline and disordered materials. Particular attention is given to systems that not only extend to the limiting insulating and metallic regimes, but also embrace the transition region between these two canonical states. Examples include the periodic table of the elements, doped semiconductors, metal solutions, expanded (supercritical) metals, transition-metal oxides, and small metallic particles or clusters. The necessary and sufficient conditions for metallic character in these systems are reviewed in terms of the Mott, Hubbard and Anderson views of the metallization process.

ISSN:0144-235X    

DOI:10.1080/01442358309353340

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

J. N. Murrell and E. A. Boucher.Properties of Liquids and Solutions. Chichester: Wiley, 1982. 288 pp. £19.75, $44.50 (hardback). ISBN 0 471 10201 6. £8.90 (softback). ISBN 0 471 10202 4.

ISSN:0144-235X    

DOI:10.1080/01442358309353341

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor