Single configurational coordinate model

Figure 11.13. The single configurational coordinate model for Cr5 fluorescence in low-field crystals, r = configurational coordinate.

Figure 6 Spectral distribution of the Eu + emission in barium thiogallates The points on the Ba3 Ga2 Se Eu band correspond to the calculation of the shape from the single-configurational-coordinate model. (Reproduced by permission of Ref. 4)...

Let us consider a dopant ion in a host lattice and assume that it shows luminescence upon illumination. What we will have to discuss is the interaction of the dopant ion with the vibrations of the lattice. The environment of the dopant ion is not static the surrounding ions vibrate about some average positions, so that the crystalline field varies. The simplest model to account for the interaction between the dopant ion and the vibrating lattice is the single-configurational coordinate model (4, 7). 

In the context of the single configuration coordinate model, pressure can potentially influence Eq, S, and hco. Changes in Eq lead to shifts of electronic energy... 

Dolan et al. [ 176] and Rinzler et al. [ 142] presented a semi-empirical approach based on a single configuration coordinate model (see Sect. 3.1) for separating the effects of local compressibihty and crystal field strength on pressure-induced changes in the T2 energy of Cr + in several fluoride elpasohte systems. Their approach is based on an empirical form, motivated by the Born-Mayer potential, for the local compressibility k(P) ... 

Figure 14 also includes a more complete lifetime prediction (solid line) based on a single configurational coordinate model (Sect. 3.1) [113,141]. The single... 

Fig. 16. Energy levels of in the context of the single configuration coordinate model, a, (5, and y label the vibrational levels of the E, T2, and A2 states, respectively. A is the zero phonon energy difference between the T2 and E states and S is the Huang-Rhys factor...

In the single configurational coordinate model, the individual E vibrational states mix differently with each of the vibrational T2 states. As a result, the radiative decay rate fj differs for each vibrational E state. The radiative decay rate for a given vibrational E state is the sum of transition rates to all vibrational states Y of the A2 ground state. Eor the transition E( ,0) 2 ), for example, we have... 

Fig. 26. The Ri-line energy Cr + Gd3Sc2Ga30i2 at 70 K as a function of pressure and the E- T2 energy separation (A). The solid line shows the predicted energy from the single configuration coordinate model using the parameters listed in the figure. The dashed line shows the prediction of a pure electronic model that does not include spin-orbit coupling. The initial blue shift is due to the effects of spin-orbit coupling...

The single configuration coordinate model illustrates the important role played by the T2 state in controlling the shift at low pressure. The initial blue... 

The Configuration Coordinate Model. To illustrate how the luminescent center in a phosphor works, a configurational coordinate diagram is used (2) in which the potential energy of the luminescent or activator center is plotted on the vertical axis and the value of a single parameter describing an effective displacement of the ions surrounding the activator, is plotted on the horizontal axis (Fig. 2). At low temperatures, near room... 

In this chapter, we first present (Section 10b) some qualitative aspects of MPE processes based on their visualization via the configuration coordinate model. We next discuss the problem more quantitatively (Section 10c). It is also to be noted that although the configuration coordinate model (i.e., visualization in terms of a single effective frequency) follows from the quantitative treatment only in certain approximations, in practice most of the literature does use such approximations in one form or another. Finally (Section lOd), we review the literature. 

Finally we draw attention to the fact that the single configurational coordinate diagram is only an approximation. In practice there is more than one vibrational mode involved and the system is not harmonic. Therefore the value of S is not so easy to determine as suggested above. However, for a general understanding the simple model is extremely useful, as we will see below. 

Fig. 18. Variation of the lifetime of the > A2 transition of Cr + Gd3Ga50i2 with pressure at room temperature. Two theoretical curves are shown. The parameter values correspond to those used in the single configuration coordinate (SGG) model. Excitation wavelength 580 nm...

In paper [49] various models of the active site of metal-containing enzyme glutathion-transferase having structures with five and six coordinated ions Mn + and Fe + are explored. In both cases it is assumed, that the respective metal ion is in its HS state. It essentially facilitates calculation since such a ground state can be reasonably modelled by a single-configuration (HER) wave function. Structural studies of the Jahn-Teller effect in TMCs by the ab initio CC methods are performed in [50,51]. 

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