The excited-state dynamics of the aminoazobenzene derivative, Metanil Yellow (MY), were studied by ultrafast Transient Absorption (TA) spectroscopy and state-of-the-art XUV tTme-Resolved Photoelectron Spectroscopy (TRPES). Experiments were carried out with two different excitation wavelengths, λ=370 nm and λ=490 nm, to investigate the non-hydrated and hydrated forms of the molecule and reveal differences in their dynamics. The dynamics were also studied in two solvents, water and ethanol, to investigate the effect of hydrogen bonding with the solvent. In TRPES experiments the dynamics were studied in water solution, using a λ=400 nm pump, thus exciting both forms. The timescales from the TRPES experiments are in good agreement with the results from the TAS measurements. Based on quantum chemical calculations the dynamics are tentatively assigned to the S2→S1 conversion followed by relaxation to a long-lived state, the nature of which (possibly a twisted intramolecular charge transfer – TICT – state) remains to be confirmed.
We use femtosecond UV-Vis absorption spectroscopy to investigate the photoreaction mechanism of a recently synthesized oxindole-based molecular switch showing a large C=C double bond photoisiomerization quantum yield (50%), and promising applications e.g. in photopharmacology. Due to an electron-donating phenol moeity, the molecular switch exhibits a push-pull electronic effect which affects its photophysical properties. In solvents of various polarities and hydrogen bonding capabilities, we observe a faster (sub-ps) photoisomerization dynamics of the deprotonated phenolate form of the compound, where the push-pull effect is enhanced. This work aims at unraveling the synthetic design strategies towards optimizing the photoreaction dynamics and quantum yiled of such molecular switches.
We report on an experimental study aimed to suppress the speckle structure produced by a coherent optical field. The technique proposed is based on the reduction of a laser output coherence utilizing enriching the emission spectrum lines. We achieved a temperature-controlled simultaneous emission of two components at 1.064 m and 1.066 m with nearly equal intensities in IR from diode-pumped Nd:YVO4 laser with intracavity second-harmonic generation The emission lines 532 nm, 532.6 nm and 533.1 nm were recorded in the second-harmonic output. The influence of the spectrum variation on the formation of a speckle field was checked. We succeeded to remove intensity zeroes and reduce the contrast (visibility) from 0.92 to 0.65 in a light scattered by a ground glass diffuser at the angle 35°. A simple consideration of the speckle field dumping mechanism is presented.
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