Watching ultrafast barrierless excited-state isomerization of pseudocyanine in real time.
The photoinduced excited-state processes in 1,1'-diethyl-2,2'-cyanine iodine are investigated using femtosecond time-resolved pump-probe spectroscopy. Using a broad range of probe wavelengths, the relaxation of the initially prepared excited-state wavepacket can be followed down to the sink region. The data directly visualize the directed downhill motion along the torsional reaction coordinate and suggest a barrierless excited-state isomerization in the short chain cyanine dye. Additionally, ultrafast ground-state hole and excited-state hole replica broadening is observed. While the narrow excited-state wavepacket broadens during pump-probe overlap, the ground-state hole burning dynamics takes place on a significantly longer time-scale. The experiment reported can be considered as a direct monitoring of the shape and the position of the photoprepared wavepacket on the excited-state potential energy surface.
Dietzek
Benjamin
B
Department of Chemical Physics, Lund University, P.O. Box 124, 22100 Lund, Sweden.
Yartsev
Arkady
A
Tarnovsky
Alexander N
AN
D007536:Isomerism; D007700:Kinetics; D015394:Molecular Structure; D011804:Quinolines / Q000737:chemistry*; D013053:Spectrophotometry; D013997:Time Factors
D011804:Quinolines; C100254:pseudoisocyanine