title: Controlling the Excited-State Reaction Dynamics of a Photochromic Molecular Switch with Sequential Two-Photon Excitation.
abstract: Sequential two-photon excitation increases the cycloreversion yield of a diarylethene-type photochromic molecular switch compared with one-photon excitation. This letter shows for the first time that an optimal delay of ∼5 ps between primary and secondary excitation events gives the largest enhancement of the ring-closing reaction. Pump-probe (PP) and pump-repump-probe (PReP) measurements also provide detailed new information about the excited-state dynamics. The initially excited molecule must first cross a barrier on the excited-state potential energy surface before secondary excitation enhances the reaction. The PReP experiments demonstrate that the reaction path of a photochromic molecular switch can be selectively controlled through judicious use of time-delayed femtosecond laser pulses.
authors: Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States.
authors: Cassandra L
authors: CL
authors: Ward
authors: Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States.
authors: Christopher G
authors: CG
authors: Elles
keywords: cycloreversion; multi-photon; photochemistry; ultrafast spectroscopy; wavepacket