Quantum yields, nanosecond laser flash photolysis

Extension from atriad (Fc—ZnP—Ceo) to atetrad (Fc—ZnP—H2P—C60) results in remarkable elongation of the final CS state (44). The multistep ET processes afford the final CS state, Fc —ZnP—H2P—Ceo which is detected as the transient absorption spectrum obtained by nanosecond laser flash photolysis [Fig. 8(rz)] (44). The Ceo fingerprint ( 1000 nm) NIR band is clearly seen, whereas the weak absorption features of the ferrocenium ion prevents its direct detection. The quantum yield of the CS state was determined to be 0.24 (44). The relatively low quantum yields results from the competition of ET from ZnP to H2P versus the BET from Ceo to H2P to give the triplet excited state ( H2P ... 

Picosecond and nanosecond transient spectroscopic studies to elucidate the nature of various intermediates formed in the photoinduced electron-transfer reaction of amines have been most extensive for the ketone-amine systems. These studies have been described in detail in a recent review by Yoon et al. [10]. Some aspects of these studies are briefly described here. In the earlier studies of Cohen and coworkers, the photochemical reactions of benzophenone with aliphatic amines were probed by fluorescence quenching, determination of product quantum yields, and nanosecond laser-flash photolysis [143-147]. They proposed that the reactions of amines with... 

Another study, which used nanosecond laser flash photolysis and steady-state photolysis experiments, showed that the decarboxylation of the tolmetin is markedly reduced upon inclusion [17]. The rate constants of the decay of the intermediate transients involved in its photodecomposition were slowed down due to the effect of the hydrophobic CD nanocavity. Similar work carried out on the NSAID ketoprofen [42] and suprofen [43] has shown that inclusion in the j -CD cavity leads to a significant decrease in decarboxylation efficiency and to the opening of new photoreactive channels. Moreover, a modification of the distribution of the photoproducts and a considerable reduction of the quantum yield of singlet oxygen sensitized production either by the starting compound or... 

Photophysical characteristics of Pis (Scheme 12.1), especially the quantum yields of their dissociation O iss, are very important. Most of the photophysical data were measured by nanoseconds or picoseconds laser flash photolysis (LFP) or phosphorescence at low temperature. The properties of representative Pis are given in Table 12.1. 

Flash photolysis with nanosecond laser excitation, monitoring absorption [112-114] and optoacoustic signals [82,90,115] of the transients, showed that in the primary reaction of P, two photoproducts are formed, presumably simultaneously in parallel pathways (see below and [136] for a caveat), with a total quantum yield of d>r 700 > 0.5 38% of I o decaying with a... 

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