摘要:

The theory of periodic orbits for conservative Hamiltonian systems and the way that it is applied to analyse vibrational spectra of highly excited polyatomic molecules is reviewed. Applications for triatomic, tetratomic molecules and van der Waals clusters are presented. It is shown that the periodic orbit method can trace localized eigenfunctions above potential barriers which are associated with saddle-node bifurcations. Such states connect separate minima on the potential energy surface, and thus, are important for studying isomerization processes.

ISSN:0144-235X    

DOI:10.1080/01442359609353188

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper reviews recent developments in the study of reactive collisions using optical methods. Although the basic approach is from the experimental viewpoint, attention is paid to the conceptual and theoretical aspects of the physics underlying modern reaction dynamics. After a brief resume of basic concepts and definitions on both scalar and vectorial quantities characterizing the chemical reaction, a significant body of this paper describes the recent achievements using laser techniques, mainly via laser-induced fluorescence, and chemiluminescence. Both high-resolution crossed-beam and high-resolution bulb studies are presented in a complementary fashion, as they provide a detailed picture of reaction dynamics through the measurement of quantum state specific differential cross-sections. Specific examples include the use of Doppler resolved laser-induced fluorescence, multiphoton ionization or Cars studies. Some examples are also included based on the use of product imaging techniques, the novel approach of obtaining quantum state resolved differential cross-sections for chemical reactions. In addition, new data on the collision energy dependence of the collision cross-section, i.e. the excitation function, obtained by highly sensitive collision energy cross-beam techniques is also presented and reviewed. Another part of the paper is dedicated to recent advances in the study of reaction dynamics using electronically excited species. Emphasis is placed not only on the opening of new channels for chemical reactions but also on the possible outcome of the reaction products associated with the different symmetries of the excited potential energy surfaces. Finally, a section is dedicated to recent developments in studies carried out in the area of van der Waals and cluster reactions. The possibility of clocking the chemical act as well as very efficient trapping of reaction intermediates is illustrated with some examples. Throughout the whole paper care is taken to discuss the most significant features of the molecular reaction dynamic observables with reference to simple reaction models and/or theoretical treatments currently used in the field.

ISSN:0144-235X    

DOI:10.1080/01442359609353189

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

One-electron resonances in electron scattering from polyatomic molecules were examined using set of interconnected models. We compared resonant states predicted from the virtual orbitals of a minimum-basis-set self-consistent-field (MBS-SCF) calculation with scattering resonances found using both a purely local model potential for the electron-molecule interaction based on an adiabatic separation of the angular and radial motion and a more accurate exact-static-exchange-plus-model-correlation—polarization interaction potential. Considering electron scattering from N2, SF6, and C6H6, we found that the MBS-SCF virtual orbitals were an excellent predictor of the symmetry and approximate location of one-electron resonances. The adiabatic radical potentials were very useful in understanding the mechanism for resonant trapping, although strong non-adiabatic coupling sometimes required more than one adiabatic potential to be considered to accurately represent the resonant dynamics. The essential feature of the trapping mechanism for each of these systems was an angular momentum barrier found in one of its adiabatic potentials.

ISSN:0144-235X    

DOI:10.1080/01442359609353190

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper provides a summary of the essence and the results of the author's reduced potential curve (RPC) method hitherto scattered in a large number of scientific papers, which he hopes may serve for the use and further development of this method by other interested scientists. The RPC method makes possible a systematic study of the internuclear potentials of the ground and excited states of diatomic systems in a unique RPC scheme. Interesting and so far unknown regularities and rules (laws suggested by the quantum mechanical background) appear in the RPC scheme. With the use of these ‘RPC rules’, the RPC formula and its parametrized generalization, the Grpc formula, may be used for various practical applications of the RPC method such as: (a) detection of (even small) errors in the potentials constructed from the spectral data or errors in the analysis of the spectrum of a diatomic system, (b) detection of errors in the values of the molecular constants, (c) detection of errors in the adiabatic potentials due to perturbations, (d) detection of anomalies, (e) estimation of the dissociation energy, (f) correction of errors in the potentials mentioned above, and (g) construction of the internuclear potential of a diatomic system and calculation of its spectrum from the spectral data of another diatomic system or from anab initiocalculated theoretical potential. The rules and the structure of the RPC scheme and the applications of the RPC method are demonstrated in numerous examples and further prospects are discussed.

ISSN:0144-235X    

DOI:10.1080/01442359609353191

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0144-235X    

DOI:10.1080/01442359609353192

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor