摘要:

One of the simplest possible reactions imaginable, that of an atomic ion with molecular hydrogen, shows a remarkable diversity in behaviour as the atomic ion is varied throughout the periodic table. Studies of these reactions reveal the fundamental changes that occur in the chemistry as the number of electrons is systematically varied. Here, we review our work on the kinetic energy dependence of these reactions as studied by using guided ion beam mass spectrometry. Substantial progress has been made in this area and now includes studies of 44 elements. This experimental technique is shown to provide unprecedented detail in reaction excitation functions over an extremely wide kinetic energy range. These studies allow an understanding of such effects as the reaction thermochemistry, electronic degeneracy, adiabaticversusdiabatic potential energy surfaces and spin-orbit coupling.

ISSN:0144-235X    

DOI:10.1080/01442359009353244

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We review the bonding for both first- and second-row transition-metal positive ions with a variety of ligands. For singly charged ions we consider a range of interaction strengths from the weakly interacting noble gases to the covalently bonded dimethyls. We also consider several dications, since many of these systems are amenable to experimental study. The bonding, particularly for covalent systems, is found to arise generally from a mixture of the lowest atomic states. Polarization, sd and sp hybridization, and s-to-d and d-to-s promotion are various means of reducing the repulsion and enhancing the bonding. The relative importance of these effects depends on the separations between the lowest states of the metal ion. The loss of atomic d-d exchange energy in the molecule is also an important factor in determining the binding energies. The diversity of transition-metal bonding arises because the relative importance of these effects depends on the separation of the atomic states with different d occupancies. The calculations are able to explain the relative magnitudes of the first- and second-ligand binding energies for transition-metal ions bound to noble-gas, water, CO and CH3ligands.

ISSN:0144-235X    

DOI:10.1080/01442359009353245

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A critical survey is given of new developments in the study of collision dynamics of diatomic radicals. The impetus for this survey comes from new experimental results on near state-to-state scattering dynamics of radicals with simple collision partners that have been obtained using the crossed-beam technique. These results, on both inelastic and reactive scattering, provide a unique opportunity to compare experimental observations with formal quantum scattering theory. Photodissociation is also briefly discussed because of its relevance to our fundamental understanding of fine-structure effects associated with radicals arising in all three processes. A few basic concepts pertaining to the dynamics of open-shell systems are outlined. The emphasis is on the underlying physical principles rather than on detailed theoretical treatments. To illustrate the strong interaction between theory and experiment a few case studies of systems investigated under crossed-beam conditions are highlighted. These new results also prompt an appraisal of what an experimentalist should be most anxious to measure and indicate specific areas in which further theoretical developments can be most profitable in the future.

ISSN:0144-235X    

DOI:10.1080/01442359009353246

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor