title: Ultrafast dynamics in multibranched structures with enhanced two-photon absorption.
abstract: The understanding of the mechanism of the enhanced two-photon absorption (TPA) in multibranched chromophore systems is of importance to the design of materials with the large TPA cross-sections and for future applications. In this communication, the mechanism of enhanced TPA properties is investigated. For a dendritic model system, the excited-state dynamics for both population (T1-process) and phase relaxation (T2-process) processes involved are investigated by a combination of time-resolved spectroscopic techniques. The results of time-resolved fluorescence anisotropy are compared with previous results obtained from other branched chromophore systems. It is found that the PRL-701 trimer system, which possesses the large enhancement of two-photon absorption cross-section, gives a faster anisotropy decay (fluorescence upconversion and transient absorption), a longer population relaxation time (fluorescence lifetime), and a weaker coupling to the solvent (a larger photon echo peak shift initial value). New strategies for rational design of large TPA materials can be achieved based on a better understanding of the mechanism of the enhancement.
authors: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Ying
authors: Y
authors: Wang
authors: Guang S
authors: GS
authors: He
authors: Paras N
authors: PN
authors: Prasad
authors: Theodore
authors: T
authors: Goodson