Vibrational Coherence of Bis-imidazole Derivative, BDPI-2Y, Observed by Ultrafast Spectroscopy.

Ultrafast pump-probe measurement was applied to investigate the excited state deactivation dynamics of bisimidazolyl radical, 1,4-bis-(4,5-diphenylimidazol-2-ylidene)cyclohexa-2,5-diene (BDPI-2Y). BDPI-2Y is non-fluorescent and the recovery of the ground state took place in the time scale of femtoseconds to picoseconds, indicating a direct ultrafast nonradiative decay from the excited state. Coherent intermolecular vibrations were also observed and the low-frequency mode at 150 cm -1 and 128 cm -1 had a phase shift of ~ p compared to the mode at 290 cm -1 . [ABSTRACT FROM AUTHOR]