Picosecond absorption anisotropy of polymethine and squarylium dyes in liquid and polymeric media

    Authors

    O. V. Przhonska; D. J. Hagan; E. Novikov; R. Lepkowicz; E. W. Van Stryland; M. V. Bondar; Y. L. Slominsky;A. D. Kachkovski

    Abbreviated Journal Title

    Chem. Phys.

    Keywords

    ROTATIONAL-DIFFUSION; TRANSIENT ABSORPTION; LINEAR DICHROISM; PHOTOPHYSICS; TIME; SPECTROSCOPY; STATE; Chemistry, Physical; Physics, Atomic, Molecular & Chemical

    Abstract

    Time-resolved excitation-probe polarization measurements are performed for polymethine and squarylium dyes in ethanol and an elastopolymer of polyurethane acrylate (PUA). These molecules exhibit strong excited-state absorption in the visible., which results in reverse saturable absorption (RSA). In pump-probe experiments, we observe a strong angular dependence of the RSA decay kinetics upon variation of the angle between pump and probe polarizations. The difference in absorption anisotropy kinetics in ethanol and PUA is detected and analyzed. Anisotropy decay curves in ethanol follow a single exponential decay leading to complete depolarization of the excited state. We also observe complete depolarization in PUA, in which case the anisotropy decay follows a double exponential behavior. Possible rotations in the PUA polymeric matrix are connected with the existence of local microcavities of free volume. We believe that the fast decay component is connected with the rotation of molecular fragments and the slower decay component is connected with the rotation of entire molecules in local microcavities, which is possible because of the elasticity of the polymeric material. (C) 2001 Published by Elsevier Science B.V.

    Journal Title

    Chemical Physics

    Volume

    273

    Issue/Number

    2-3

    Publication Date

    1-1-2001

    Document Type

    Article

    Language

    English

    First Page

    235

    Last Page

    248

    WOS Identifier

    WOS:000172324600014

    ISSN

    0301-0104

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