Effect of temperature on the optical parameters of the molecules in the homologous series of 10 dicarbocyanine
polymethine dyes was studied. The thermally and photostimulated reversible changes in the isomer compositions and
optical properties of solutions and molecular layers were investigated experimentally. The effect of temperature on the
optical density, absorption spectra, fluorescence intensity, fluorescence quantum yield, photoisomerization quantum
yield, and kinetics of changes in the isomer composition of the solutions was studied in the range (-60÷+60)°C. It was
shown that the thermal sensitivity of the optical parameters of the polymethine molecules depends on the electrondonating
ability of end groups. The reversible relative changes in the optical density of the solution with temperature are
(0.4-1.4) % /deg. The range of relative changes of the fluorescence intensity is (1-2.3) % /deg.
The new method of direct transformation of a thermal image into visible image with the aid of three-level molecular
systems was proposed involving optical excitation from the low state into the intermediate fluorescent state and the
thermally stimulated transitions from this state into the nearby upper state. The visible image can be observed by the
optical methods, either by measuring the fluorescence intensity or as a change in the optical density of a screen of the
detector in the region where the thermal image is formed.. The bolometric matrix-receiving medium was polymethine
dye, which undergoes isomerization, i.e., changes structure under the action of thermal and optical radiation.
Stepwise reversible rearrangement of dicarbocyanines upon excitation of instable primary photoisomers is studied using nanosecond pump-probe laser spectroscopy. The structure of secondary photoisomers, the probabilities and activation energies of the second photoisomerization stage are found. The mechanism of recovering stable molecules upon relaxation of secondary photoisomers is determined.
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