Rydberg electron/charge transfer

Fig. 13.8 Overall perspective view of the charge exchange apparatus. A thermal Na beam is laser excited in the interaction region to produce a target for Rydberg-to-Rydberg charge transfer experiments. The number of target Rydberg atoms is determined by pulsed field ionization between the parallel plates and by collection of the resultant ions in the electron...

Vibrational mode selectivity can also be used to promote electronic processes. Vibrational autoionization is a process whereby a bound electron acquires sufficient energy to escape by extracting one quantum of vibrational energy from the ionic core of the molecule. For such an energy transfer to occur, the electron must first collide with the core. Scattering of the electron with the core can be promoted if the amplitude of the nuclear motion overlaps the electronic charge density. An example of this process studied by Steven Pratt is vibrational autoionization of the 3d Rydberg electrons of ammonia, which is enhanced... 

There are other aspects of the application of the MCSCF method that have not been discussed in this review. The most notable of these probably is the lack of a discussion of orbital basis sets. Although the orbital basis set choice is very important in determining the quality of the MCSCF wavefunction, the general principles determined from other electronic structure methods also hold for the MCSCF method with very little change. For example, the description of Rydberg states requires diffuse basis functions in the MCSCF method just as any other method. The description of charge-transfer states requires a flexible description of the valence orbital space, triple or quadruple zeta quality, in the MCSCF method just as in other methods. Similarly, the efficient transformation of the two-electron integrals is crucial to the overall efficiency of the MCSCF optimization procedure. However, this is a relatively well understood problem (if not always well implemented) and has been described adequately in previous discussions of the MCSCF method and other electronic structure methods . ... 

Rydberg charge exchange reactions with CS2 show another most unusual feature. Carmen et al. reported a pronounced isotope effect in the Rydberg electron transfer reaction between Rb and and For a narrow range of ( near = 17, the rate constant... 

To provide a more general assessment of the TD-DFT results, it is worth noting that, while it usually gives accurate results for excitation energies, the method is known to fail for higher electronic states with doubly excited charge-transfer or Rydberg character, and for excitations in extended Tr-systems [57]. 

The very nature of the photochemical processes the multi-state multiconfigurational character and the occurrence of non-adiabatic behavior -leads to the fact that the field of computational photochemistry is still far from saturated with respect to computational tools and method developments. The need to treat several excited states, of different electronic character (covalent, ionic, charge-transfer, Rydberg, etc.), without bias requires the applied theory to be developed at a rather high level of sophistication. While TD-DFT to a large extent is attractable for Born-Oppenheimer molecular dynamics and trajectory surface hopping (TSH), due to its speed, it has its limitations in what type of transitions are correctly... 

For highly charged ions it has been pointed out that the charge-transfer electron capture leads to Rydberg levels whose separation energies are in the optical spectral range. 

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