Configurational coordinate diagram nonradiative transitions

In general the temperature dependence of the nonradiative processes is reasonably well understood. However, the magnitude of the nonradiative rate is not, and can also not be calculated with any accuracy except for the weak-coupling case. The rea.son for this is that the temperature dependence stems from the phonon statistics which is known. However, the physical processes are not accurately known. Especially the deviation fiom parabolic behaviour in the configurational coordinate diagram (anhar-monicily) may influence the nonradiative rate with many powers of ten. However, it will be clear that the offset between the two parabolas (AR) is a very important parameter for the nonradiative transition rate. This rate will increase dramatically if AR becomes larger. 

Fig. 4.10. Schemaiic configurational coordinate diagram for (4/ ). Drawn parabolas relate to the 4/ configuration the broken parabolas indicate two possible situations for the 4f configuration (1 and II). Excitation into I yields d- /emission from 1 (arrow 1). Excitation into II (with larger offset) yields a nonradiative transition to the 4/ configuration (arrow 2) which may be followed by intraconfigurational 4/ emission...

FIGURE 22.11 Configuration coordinate diagram of low-energy-excited states in TT-conjugated polymers. Various excitation manifolds are marked by dashed line boxes. Narrow vertical arrows show optical transitions, whereas broad arrows indicate nonradiative relaxation pathways. (From Frolov, S.V., et al., Phys. Rev. B, 65, 205209, 2002. With permission.)... 

Fig. 4.33 Configurational coordinate diagram representing the structure of Pr in the host, which is represented by the impurity (praseodymium)-trapped exciton PTE a represents the situation at ambient pressure, b at pressure P i (reprinted from Ref. [202], copyright 2013, with permission from Elsevier), and c at pressure P2- The radiative and nonradiative transitions are indicated by solid and dashed arrows, respectively...

Fig. 14.2 Configurational coordinate diagrams of bismuth-doped alkali borate glasses a for lower and b for higher content of alkali oxide. Po and 2 states are marked as broken lines because the transitions from Sq to the states are forbidden. Horizontal lines denote the vibrational levels. The blue solid lines refer to the nonradiation relaxations. Upward-directed red solid lines refer to the excitation processes, and downward-directed black solid lines refer to the emission process. AQ indicates the offset of parabolas. Reprinted from Ref. [44] by permission of OSA Publishing...

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