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Important factors for the formation of radical cation of stilbene and substituted stilbenes during resonant two-photon ionization with a 266- or 355-nm laser

Paper ID Volume ID Publish Year Pages File Format Full-Text
28740 44089 2006 10 PDF Available
Title
Important factors for the formation of radical cation of stilbene and substituted stilbenes during resonant two-photon ionization with a 266- or 355-nm laser
Abstract

The resonant two-photon ionization (TPI) of trans-stilbene and substituted trans-stilbenes (S) in acetonitrile was studied by laser flash photolysis using a Nd3+:YAG laser (266- or 355-nm). The transient absorption spectra of S radical cations (S+) with a peak around 450–540 nm were observed. Formation of S+ can be explained by two-step two-photon excitation from the ground state (S0) to the lowest singlet excited state (S1) and from the S1 to the higher singlet excited state (Sn), from which ionization occurs. The formation quantum yield of S+ (ϕion) was 0.005–0.11. Little or no relation between ϕion and Eox was observed for non-substituted (1), mono-p-substituted (2–7) and di-p-substituted (8–11), methoxy-substituted (12–16), and donor–acceptor-p-substituted trans-stilbenes (17–21). On the other hand, ϕion increased with the increase of the fluorescence lifetime (τf) for all S. Interestingly, relatively large ϕion was observed for 17–21 even though they have relatively short τf among those of S. It is suggested that the CT electronic character of the S1 state and, therefore, the large molar absorption coefficient are responsible for the efficient TPI of 17–21.

Keywords
Radical cation; Stilbene; Resonant two-photon ionization; Nd3+:YAG laser photolysis; Substituent effect; Property of the singlet excited state
First Page Preview
Important factors for the formation of radical cation of stilbene and substituted stilbenes during resonant two-photon ionization with a 266- or 355-nm laser
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 179, Issues 1–2, 1 April 2006, Pages 115–124
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering