title: Investigation of two-photon absorption properties in branched alkene and alkyne chromophores.
abstract: Novel alkene and alkyne branched structures have been synthesized, and their two-photon absorption (2PA) properties are reported. This series of alkene and alkyne trimer systems tests the mechanistic approach for enhancing the 2PA process which is usually dictated by the pi-bridging, delocalization length, and corresponding charge transfer on the 2PA cross sections. The results suggest that alkene branched systems have higher 2PA cross sections. While steady-state absorption and emission measurements were not successful in predicting the observed trend of 2PA cross sections, time-resolved measurements have explained the trends observed. It was found that, upon photoexcitation, there is an ultrafast charge localization to an intramolecular charge-transfer (ICT) state, followed by the presence of a solvent and conformationally relaxed ICT state in these branched systems.
authors.affiliation: Department of Chemistry and Macromolecular Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Ajit
authors.initials: A
authors.lastname: Bhaskar
authors.forename: Guda
authors.initials: G
authors.lastname: Ramakrishna
authors.forename: Zhikuan
authors.initials: Z
authors.lastname: Lu
authors.forename: Robert
authors.initials: R
authors.lastname: Twieg
authors.forename: Joel M
authors.initials: JM
authors.lastname: Hales
authors.forename: David J
authors.initials: DJ
authors.lastname: Hagan
authors.forename: Eric
authors.initials: E
authors.lastname: Van Stryland
authors.forename: Theodore
authors.initials: T
authors.lastname: Goodson