Jablonski-term diagram

FIG. 2. Correlation between absorption, fluorescence, and phosphorescence spectra and the electronic and vibrational energy levels in the term diagram (called Jablonski term scheme) absorption (A), fluorescence (F), and phosphorescence (P) spectra. 

Explain the processes of absorption, radiative transitions and radiationless transitions in terms of Jablonski diagrams. 

Although similar principles hold for transition states of chemical reactions, use of the term metastable state to refer to the transition state is actively discouraged by scientific convention. See Transient Chemical Species Jablonski Diagram... 

The methods of chemical kinetics can also be applied to the study of transitions between the different electronic states. This study must now be guided by different principles because the initial (reactant) and final (product) states cannot be described by the same PES. Such transitions may occur either with the absorption or emission of light, designated as radiative transitions, or with the conversion of the energy difference between the two states into heat, in which case, they are termed as radiationless transitions. In photochemistry and spectroscopy, the transitions between the electronic states are conveniently illustrated by the so-called Jablonski diagram [1], where the radiative transitions are represented by vertical arrows and the radiationless ones by wavy and/or by dashed lines (Figure 15.1). 

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