Charge-transfer state population

Because of the spectral relaxation due to the appearance of a high dipole moment in the charge-transfer state, the dynamics of the TICT state formation has been studied by following the fluorescence rise in the whole A band. In Fig. 5.6 are plotted, in the 10 ns time range, the experimental curve iA(t) at -110°C in propanol (tj = 1.5 x 103 cp) and the decay of the B emission at 350 nm. The solid curve representing the evolution of the TICT state expected in a constant reaction rate scheme shows a slower risetime with respect to that of the recorded A emission. To interpret the experimental iA(t) curves, the time dependence of the reaction rate kliA(t) should be taken into account. From the coupled differential equations for the populations nB(t) and nA(t) of the B and A states (remembering that the reverse reaction B <—A is negligible at low temperatures) ... 

One advantage of the vanadate system is its V-O charge-transfer state around 35 700 cm-1 (280 nm) which can be used to populate the Lnra excited states. In this way, NIR emission form Ndm, Ho111, and Er111 is observed in chloroform solutions, upon excitation at 280 nm (Stouwdam et al., 2005). 

CH2-O-CH2 and anthracene is sufficiently strong in the jet to prevent population of the charge-transfer state. The mechanism of this interaction needs further clarification. 

The photophysics of a series of /ra/w-stilbenes (11) have been reported. Energy transfer between Erythrosin B and some stilbene derivatives has been examined in detail. The intramolecular electron transfer encountered on irradiation of the stilbene derivative (12) in methylene chloride has been studied. Irradiation populates a charge transfer state that undergoes E,Z-isomerism. When methanol is added to the system irradiation not only brings about isomerism but also converts the trisilanyl group into the silane (13). The results of a study of the photochemical behaviour of a series of halostilbenes have been published. ... 

Intramolecular electron transfer occurs on irradiation of the stilbene derivative (319) in methylene chloride. Irradiation populates a charge transfer state that undergoes ,Z-isomerism and when methanol is added to the system not only is isomerism, observed but also the trisilanyl group in (319) is converted into the silane (320). The photochemical reactivity of the vinyldisi-lanes (321) has been examined and direct irradiation of (321a) in cyclohexane is reported to yield two products identified as the (2+2)-dimers (322) and (323). Irradiation of (321c) in cyclohexane with added methanol afforded the methoxy addition product (324). Both these results are in agreement with the intermediacy of silenes such as (325) and (326) in these experiments and... 

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