TY  - JOUR
A1  - Ceyman, Harald
A1  - Rosspeintner, Arnulf
A1  - Schreck, Maximilian H.
A1  - Mützel, Carina
A1  - Stoy, Andreas
A1  - Vauthey, Eric
A1  - Lambert, Christoph
T1  - Cooperative enhancement versus additivity of two-photon-absorption cross sections in linear and branched squaraine superchromophores
JF  - Physical Chemistry Chemical Physics
N2  - The linear and nonlinear optical properties of a series of oligomeric squaraine dyes were investigated by one-photon absorption spectroscopy (1PA) and two-photon absorption (2PA) induced fluorescence spectroscopy. The superchromophores are based on two indolenine squaraine dyes with transoid (SQA) and cisoid configuration (SQB). Using these monomers, linear dimers and trimers as well as star-shaped trimers and hexamers with benzene or triphenylamine cores were synthesised and investigated. The red-shifted and intensified 1PA spectra of all superchromophores could well be explained by exciton coupling theory. In the linear chromophore arrangements we also found superradiance of fluorescence but not in the branched systems. Furthermore, the 2PA showed enhanced cross sections for the linear oligomers but only additivity for the branched systems. This emphasizes that the enhancement of the 2PA cross section in the linear arrangements is probably caused by orbital interactions of higher excited configurations.
KW  - 2-photon absorption
KW  - Vibronic contributions
KW  - One-photon
KW  - Molecules
KW  - Intensity
KW  - Multibranched structures
KW  - Optical properties
KW  - Dyes
KW  - Chromophores
KW  - Design
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188299
VL  - 18
IS  - 24
ER  -