Title

Picosecond Absorption Anisotropy Of Polymethine And Squarylium Dyes In Liquid And Polymeric Media

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. © 2001 Published by Elsevier Science B.V.

Publication Date

11-15-2001

Publication Title

Chemical Physics

Volume

273

Issue

2-3

Number of Pages

235-248

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/S0301-0104(01)00481-5

Socpus ID

0035890148 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0035890148

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