Sensitivity transient absorption spectra

Figure 7 Photosensitized reduction of oxazine dye using humic acid as sensitizer. The transient absorption spectrum was recorded following 532-nm laser pulse excitation of humic acid containing the dye and 1102.

Probing at Various Wavelengths. The transient absorption spectrum can be recorded with a superior sensitivity using various wavelengths for the... 

The intersystem crossing efficiencies of 3 and 21 were very small (1%). The triplet-triplet spectra of these dyes were obtained using the triplet-triplet energy transfer method, employing 9,10-dibromoanthracene (DBA) as the sensitizer (Fig. 4). The transient absorption spectrum, recorded immediately af-... 

Related to our work on the bipyridyl acetylides, we have also demonstrated that proper selection of the acetylide ligand makes possible the design of Ptn terpyridyl complexes that exhibit acetylide 3IL excited states [20]. The perylene complexes 3.7 and 3.8 do not display photoluminescence, however, indirect evidence that the triplet excited state is indeed populated was indicated through the sensitization of singlet oxygen. Transient absorption measurements (Fig. 7) confirmed that regardless of the polyimine ligand used, the lowest excited state in these molecules is 3IL localized in the perylenylacetylide moiety. It is clear in Fig. 7a and b that the identical features are observed in the absorption difference spectra of 3.7 and 3.8, whereas the difference spectrum of the phenylacetylide complex is clearly distinct, illustrative of the marked differences between 3IL and 3CT excited absorptions. 

One laser photophysical study (6) has already been reported by Fischer et al. in which a variety of natural water samples and solutions of humic substance standards were excited at 355 nm (near the absorption maximum for excitation of humic substance fluorescence). Extensions of their work appear in this symposium. They resolved two components of transient absorption common to all the samples studied a component with maximum absorbance at 475 nm with a lifetime of several microseconds and a signal at 700 nm which was attributed to a solvated electron on the basis of is its sensitivity to N2O and on its absorption spectrum. 

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