Isomerization triplet-excited region

Dynamic Triplet-Excited Region in Retinal As Revealed by Deuteration Effects on the Quantum Yields of Isomerization via the T State (Okumura, Koyama, unpublished results)... 

Extremely Efficient 15-C/sto All-Trans Isomerization in the Triplet-Excited Region. 183... 

The luminescence decay occurs as a single exponential with a triplet state lifetime of 0.53 0.02 //s. The transient difference absorption spectrum of Pd2(dba)3 shows an intense peak at 600 nm, which decays by a double exponential process. The observed lifetimes of the two processes are 1.0 0.1 ns and 0.50 0.03 The long-lived decay corresponds to an MLCT triplet deactivation process, whereas the short-lived pathway is likely associated with an isomerization of the complexed dba, rather than with a fluorescence decay from the excited singlet state. These excited state lifetimes in the nanosecond region are much shorter than that found for the cis-trans isomerization in free dibenzylideneacetone (5.2 //s). This isomerization must therefore be occurring at a coordinated and not a free dba. For Pt2(dba)3 only a single exponential decay is observed with a lifetime of 0.26 ps. This decay is due to an MLCT triplet deactivation process. In this case no short-lived decay process is observed. This difference may be due to the increased strength or to the decreased lability of the metal-alkene bond in the zerovalent platinum complex. 

Examples of phenomena which have been studied by analyzing absorption spectral changes in the ps time region are isomerization of trans-stilbene from the state (6) and vibrational relaxation of the triplet benzophenone (7) as well as the excited singlet anthracene (8). It is... 

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