Photoreaction via the triplet state

In Section 2.1.3.3 the photoreaction of an isomerisation from the singlet state for 

According to the procedure explained in Section 2.1.1.1 rows and columns are filled. All the excited molecules are supposed to form A first. Therefore both steps 

Therefore as in the case of the singlet pathway, one partial reaction can be omitted in the scheme. Application of the Bodenstein hypothesis to the intermediates A and A gives 

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