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|Type:||Artigo de periódico|
|Title:||Contribution Of The Jahn-teller Effect In The Electronic Raman Scattering In Mgo:co2+|
|Abstract:||A theoretical study of the electronic Raman scattering of MgO with substitutional Co2+ impurities is presented in this paper, and the Jahn-Teller interaction is employed to calculate the line shape. The contribution to the Raman scattering discussed here is different from the phononic contribution studied by other authors. In their calculation, they have implicitly assumed the validity of the Born-Oppenheimer approximation, an assumption that is not valid for the lowest levels of Co2+ in MgO. The electronic Raman intensity is given by an approximate formula that contains the time correlation function of transition operators between the few electronic states of Co2+ that are close to the ground state. To obtain these correlation functions we employ Greens functions, decoupling the equation of motion at a convenient stage of the calculation. Only the normal modes of the complex formed by Co2+ and the six nearest O2- ions have been included in the Jahn-Teller interaction, and they have been expressed as a series of all the lattice phonons. The theoretical phonon spectrum of MgO has also been replaced by a simpler analytical expression that gives its more important features. Most of the parameters that appear in the calculation have been derived from other properties of the system. There is a fairly good agreement between the measured Raman spectrum and the one calculated here. In particular, the relative position of the two 6 '8 and 6 '8 transitions is well explained by the model. The theory also predicts a splitting of the 6 '8 line into a doublet, a fact that is experimentally observed. © 1985 The American Physical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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