Single configurational coordinate model luminescence

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). 

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... 

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