Excitation, electronic hopping model

Abstract. We present a quantum-classieal determination of stable isomers of Na Arii clusters with an electronically excited sodium atom in 3p P states. The excited states of Na perturbed by the argon atoms are obtained as the eigenfunctions of a single-electron operator describing the electron in the field of a Na Arn core, the Na and Ar atoms being substituted by pseudo-potentials. These pseudo-potentials include core-polarization operators to account for polarization and correlation of the inert part with the excited electron . The geometry optimization of the excited states is carried out via the basin-hopping method of Wales et al. The present study confirms the trend for small Na Arn clusters in 3p states to form planar structures, as proposed earlier by Tutein and Mayne within the framework of a first order perturbation theory on a "Diatomics in Molecules" type model. 

Lastly, the action spectra in Ca-HF close to the energy threshold to chemiluminescence display very narrow lines, indicating the partial closure of the corresponding reactive excited-state channel. This indicates that the observed channel luminescence is independent of the ground-state channel that could also contribute to the broadening of the lines in the spectrum and confirms the model of the 4s electron hop separated from the 3d hop. We shall now examine the effect of this hop on the efficiency of production of excited states. 

Study the dissociation dynamics of such a system, the development of simple models can best be accomplished using semiclassical or classical techniques. In Section IV C a curve-hopping model is developed, based on a collisional reorientation of the electronic angular momentum. It assumes that a bath atom collides with just one of the diatoms and reorients its electronic angular momentum on a time scale that is short compared to the relative motion of the diatoms. The model is applied to iodine photodissociation dynamics in Section IV D. The dissociation dynamics of polyatomic systems with their internal degrees of freedom is more complex than for diatomics. If these degrees of freedom are not thermally equilibrated and are coupled to the dissociation coordinate, then their dynamics cannot simply be projected out, but rather they can act as an indirect source of excitation of the dissociation coordinate. 

In order to evaluate the hopping integral Hki we have assumed a fairly simple model, in which the excess charge on the atom/molecule excites the electrons. Other models for evaluation of the non-adiabatic coupling terms (see eq. (11.6)) could be introduced instead and used when evaluating the effective potential (11.75). 

The local or extended nature of molecular-ion (or exciton) states in molecular solids is determined by a competition between fluctuations in the local site energies of these states (which tend to localize them) and the hopping integrals for inter-site excitation transfer (which tend to delocalize them). In order to define this fluctuation-induced localization concept more precisely, consider the model defined by the one-electron Hamiltonian... 

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