Fast photoprocesses in a symmetric indotricarbocyanine dye (hitc) in solutions

Spectral-kinetic and photochemical properties of HITC dye with iodide and perchlorate counterions have been studied in environments where the dye molecules exist in different ionic forms. In ethanol, the dye molecules exist as free ions; in dichlorobenzene, as contact ion pairs. Superfast transformation of non-stationary spectra in an HITC dye bleaching band is found. The observed effects are interpreted within the framework of concepts on "burning out" a notch in the contour of a non-uniformly widened vibronic band of S0 → S1-absorption. Qualitative differences in recorded absorption spectra from the dye excited electronic states for weakly and highly polar solvents are found. It is shown that the observed differences are caused by superfast charge transfer in the contact ion pairs that results in the formation of free radicals

Fast photoprocesses in a symmetric indotricarbocyanine dye (hitc) in solutions

Spectral-kinetic and photochemical properties of HITC dye with iodide and perchlorate counterions have been studied in environments where the dye molecules exist in different ionic forms. In ethanol, the dye molecules exist as free ions; in dichlorobenzene, as contact ion pairs. Superfast transformation of non-stationary spectra in an HITC dye bleaching band is found. The observed effects are interpreted within the framework of concepts on "burning out" a notch in the contour of a non-uniformly widened vibronic band of S0 → S1-absorption. Qualitative differences in recorded absorption spectra from the dye excited electronic states for weakly and highly polar solvents are found. It is shown that the observed differences are caused by superfast charge transfer in the contact ion pairs that results in the formation of free radicals

Measurement of non-equilibrium carriers dynamics in Ce-doped YAG, LuAG and GAGG crystals with and without Mg-codoping

Non-linear absorption spectroscopy in pump and probe configuration has been used to test the population of non-equilibrium carriers in Ce-doped Y$_{3}$Al$_{5}$O_${12}$ (YAG), Lu3Al5O12 (LuAG), and Gd3AlxGa(5-x)O12 (GAGG) crystals with and without codoping by Mg2+ ions. A faster rise time of the induced optical density has been observed in all crystals codoped with Mg with respect to that in Mg-free samples. A significant difference in the time evolution of the differential optical density in GAGG with respect to YAG and LuAG crystals has also been measured. In both GAGG:Ce and GAGG:Ce,Mg an absorption band with maximum in the blue-green range and a decay time of 1.4 ps is present. This band is due to the absorption by free electrons before they are trapped or re-captured by Ce3+ ions. A broad absorption band in the yellow-red region with very short rise time and a decay time longer than 150 ps has been observed in all the Ce-doped garnets under study and can be attributed to the absorption from the Ce3+ excited states