Temperature dependence, photophysical processes

Phillips, D., Roberts, A. J., Soutar, I. Transient decay studies of photophysical processes in aromatic polymers. V Temperature dependence of excimer formation and decay in copolymers of 1-vinyl naphthalene. As yet unpublished 1980... 

Emeline A. V., Polikhova S., Andreev N., Ryabchnk V. K. and Serpone N. (2002b), Photoinduced processes in heterogeneons gas-solid systems. Temperature dependence (100-600 K) and modelling of a snrface chemical reaction on zirconia that triggers photophysical events in the solid , J. Phys. Chem. B 106, 5956-5966. 

Temperature dependence, photophysical processes, 302-3 stereoselectivity, 326-27 Telra-t-butyltetrahedrane. 385 Tetracene, 254 absorption spectrum, 72, 103 Tetracene radical anion and cation. 103 Tetracycioociene, 423 Tetramethylcyclobutane, 406 TetramethyM,2-dioxeiane, 428. 482-83 Tetrameihylethyiene, 326-27 Tetranitromethane, 465 n.a.a a -Tetraphenylbenzocyclobuiene,... 

The recovery time following upon bleaching induced by Si-Sji absorption of p-terphenyl in cyclohexane at room temperature is found to be about 380 ps. The temperature dependence of photophysical processes in perylene, tetracene, and some derivatives is shown to arise from thermal activation of the S1-T2 intersystem crossing process and also for the Si-Sq internal conversion, which is particularly important in rubrene. ... 

Photophysical and photochemical processes in polymer solids are extremely important in that they relate directly to the functions of photoresists and other molecular functional devices. These processes are influenced significantly by the molecular structure of the polymer matrix and its motion. As already discussed in Section 2.1.3, the reactivity of functional groups in polymer solids changes markedly at the glass transition temperature (Tg) of the matrix. Their reactivity is also affected by the / transition temperature, Tp, which corresponds to the relaxation of local motion modes of the main chain and by Ty, the temperature corresponding to the onset of side chain rotation. These transition temperatures can be detected also by other experimental techniques, such as dynamic viscoelasticity measurements, dielectric dispersion, and NMR spectroscopy. The values obtained depend on the frequency of the measurement. Since photochemical and photophysical parameters are measures of the motion of a polymer chain, they provide means to estimate experimentally the values of Tp and Tr. In homogeneous solids, reactions are related to the free volume distribution. This important theoretical parameter can be discussed on the basis of photophysical processes. 

The origin of the change in fluorescence emission at the temperature T lies in the photophysical process itself, i.e. in quenching phenomena, the extent of which shoj ld depend on the nature of the molecules next to the label. In fact, PS is surrounded by a mixture of PS and PVME in the homogeneous blends, but mainly by PS molecules in the phase-separated systems. Thus, a simple explanation of the change in fluorescence intensity would be that PS emission is greater in PS than in PS-PVME mixtures or, in other words, that PVME is responsible for the quenching of the fluorescence emission. 

---