Expanding the State Diagram

The generalizations about photochemical reactions emerged in the 1950s are perhaps too narrow. The key photochemical steps, as shown in Sect. 7.3, involve absorption of one photon (according to the Stark-Einstein law, 10 -10 s ), internal conversion, and/or intersystem crossing down to the lowest excited singlet or the lowest triplet (Kasha-Vavilov rule, or ki c up to 10 s ) and emission or 

It has been long known that some photochemical processes require consideration of interactions between excited states, such as delayed fluorescence. These were clearly distinguished in the work by Lewis, Kasha, and Parker [1], 

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