Specific features of the two-photon absorption of cationic symmetric polymethine dyes |
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| Authors: | V A Svetlichny? O K Bazyl’ V Ya Artyukhov T N Kopylova N A Derevyanko A A Ishchenko |
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| Institution: | (1) Siberian Institute of Physics and Technology, Tomsk State University, Tomsk, 634050, Russia;(2) Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev, 02094, Ukraine |
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| Abstract: | The two-photon absorption of a number of cationic symmetric polymethine dyes based on 3H-indolium and benzothiazolium is experimentally studied upon excitation by nanosecond radiation from a Nd:YAG laser (1064 nm, 12 ns). The two-photon absorption cross section of dye molecules is determined by the two-quantum standard method. The influence of the spectral-luminescent properties and structure of the polymethine dyes on the two-photon absorption cross section is discussed. It is shown that, upon excitation in the range of the long-wavelength band of the dyes studied (the S 0 → S 1 transition), the maximum of their two-photon absorption is blue shifted. The reasons for a considerable increase in the two-photon absorption of symmetric polymethine dyes upon their excitation in the range of the S 2 state are discussed. Using the data of quantum-chemical calculations, it is shown that, along with changes in the selection rules for two-photon transitions, this increase is connected with an increase in the size of the delocalized π electron cloud of HOMOs involved in the S 0 → S 2 transition. |
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