Luminescence configuration diagram

Energy Configuration Diagram. This model, based on the energy level diagrams of atoms and molecules, is applicable to luminescence processes in which excitation and emission take place at the same luminescence center. 

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... 

Fig. 6. Configuration coordinate diagram of a luminescent centre. Non-radiative return from the excited state to the ground state is possible via the crossover S. This requires an activation energy AE which can be supplied at higher temperatures. Exc excitation, em emission...

The energy relationships in a luminescence process are presented in a configurational coordinate diagram (Fig. 83). This illustrates the relationship between the potential energy E of the luminescence center (ordinate) and a space coordinate (abscissa), which gives the representative separation between the atom involved and its nearest neighbors or the deflection from its spatial equilibrium position. 

In this section the quenching temperature of the luminescence in various uranium-doped oxides will be discussed in terms of a single configurational coordinate (SCC) diagram. The parabolae representing the groimd state and the excited states can in principle be placed using the band shapes and positions of the relevant features observed in the luminescence spectra. 

The recent investigations have shown that the temperature quenching of the uranate luminescence can be described in a satisfactory way in terms of single configurational coordinate diagrams, although we realize that this is quite a crude approximation. Especially the temperature dependence of the electronic factor which is constant in the Mott-Seitz and Struck and Fonger methods should probably be taken into account. 

The last example is the configuration, of which Mn, used in many luminescent materials, is a well-known representative. The Tanabe-Sugano diagram is given in Fig. 2.10. In octahedral coordination the ground level is A. All optical absoiption transitions are parity and spin forbidden. In fact the Mn ion is practically colorless. 

This chapter is organized as follows. First a general discussion will be given on the basis of the configurational coordinate diagram (see Chapter 2). Then we will consider a number of different classes of luminescent ions. At the end some special effects, like afterglow and stimulated emission, are treated. 

The luminescence of the trtuisition metal ions will be discussed using the Tanabe-Sugano diagrams (Sect. 2.3.1), First we will consider ions which have played or still play an important role in luminescent materials, viz. and Mn + with d configuration and with configuration. Then we will mention some ions... 

Halide complexes of main-group metal ions with an s electron configuration are frequently luminescent under ambient conditions [56, 57]. The absorption and emission spectra (Table 1) [57] can be explained on the basis of a simple energy level diagram of a free s ion (Scheme 1). The emission comes from the... 

Fig. 4.2 a Energetic structure of the luminescence center in the lattice and possible electronic transitions. The CTT and the IT are indicated by red arrows band-to-band and internal transitions in the impurity are indicated by black arrows, b Configurational coordinate diagram representing the ground and excited states of the system from Fig. 4.2a... 

---