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"Switching dynamics of the photochromic Vincent De Waele, Matthias Beutter, Uli Schmidhammer, Eberhard Riedle, Jörg Daub1,1-dicyano-2-(4-cyanophenyl)-1,8a-dihydroazulene probed by sub-30 fs spectroscopy" Chem. Phys. Lett. 390, 328 - 334 (2004) Abstract: We report the first time resolved investigation of the ring opening dynamics of the 1,1-dicyano-2-(4-cyanophenyl)-1,8a-dihydroazulene (CN-DHA) towards its vinylheptafulvene (CN-VHF) isomer. The kinetics are measured by sub-30 fs transient absorption spectroscopy for numerous probe wavelengths from 485 to 690 nm. The ring opening takes place within 1.2 ps on the CN-DHA-VHF S1 potential energy surface. It is followed by the internal conversion from CN-VHF-S1 to CN-VHF-S0 in 13 ps. We observe coherent oscillations of low frequency modes (150, 190, 330 and 500 cm-1)that are closely associated with the skeleton motions driving the CN-DHA structural changes immediately after the 30 fs UV excitation. BMO authors (in alphabetic order): Matthias Beutter Vincent de Waele Eberhard Riedle Uli Schmidhammer Order Hardcopy |