Relaxation Processes Of Photoexcited States Research Articles

Relaxation process of photo-excited states in GeSe 2 glass investigated by time-resolved photoluminescence

Time-resolved photoluminescence measurement is done on glassy GeSe 2. The decay curve consists of a process whose decay time is about ∼0.3 ms and a faster process whose decay time is less than 1 μs. The decay time of the slower process becomes short with increasing excitation energy. The ratio between the slower process and the faster process increases with increasing excitation energy especially in the higher emission energy region. The relaxation process from the excited state just after the photon absorption to the trapped excited state is discussed.

Relaxation dynamics into two types of luminescence states in C 60 single crystals below 80 K

Luminescence spectra from pure C 60 single crystals and their time behavior have been studied in the temperature range below 80 K under the excitation into two distinctive energy ranges. In case of the excitation into the higher-lying band states, two kinds of fluorescence bands, called types A and B, were observed with their onsets at 733 and 684 nm around LHeT. These bands exhibit the anti-correlated temperature dependence, indicating thermally activated population transfer from the initial state of type B to that of type A. On the other hands, the selective excitation into the tail part ( ~ 733 nm) below the fundamental absorption edge stimulates not only a series of Raman lines but also the resonant luminescence which evolves into the type A luminescence with inhomogeneous behavior. It is noteworthy that for just resonance a novel vibronic structure with Δ ~ 120 cm −1 is clearly resolved. The present study strongly suggests that fluctuation in the local intermolecular orientational correlation of molecules is essential to the relaxation processes of photo-excited states in C 60 single crystal.

Photo-Generation of Solitons and Polarons in the Quasi-1-D MX Compounds

The effect of interchain interaction on the nonlinear excitations in the one-dimensional (1-D) Peierls-Hubbard system is investigated by the photo-induced absorption (PA) measurements of the halogen-bridged metal complexes (the MX compounds; M = Pt and X = Br or I), changing the strength of the interchain coupling via the hydrogen-bonds between the charge- density wave (CDW) states. Systematic analysis of the PA signals provides a clear evidence for photogeneration of solitons and polarons which have been theoretically predicted. From the excitation profile of the PA signals, informations are obtained useful for general understanding of the relaxation processes of photo-excited states and the excitonic effect in the 1-D CDW state

Relaxation Processes of Photoexcited States in Halogen-Bridged Mixed-Valence Metal Complexes

Abstract Excitation spectra of the self-trapped exciton luminescence bands and those of photo-induced absorption bands of halogen-bridged mixed-valence metal complexes have been measured. The excitation spectra of luminescence bands begin to decrease from energies smaller than the peak energies of the charge transfer exciton absorption bands. The excitation spectra of photo-induced absorption bands begin to rise from the same energies. These show the competition between the self-trapped excitons and the photo-induced defect states in their generation processes.