IVR Dynamics of Vibrational Levels of the ν1 Mode in (CF3)2CCO Molecules Excited by Resonant IR Femtosecond Radiation

The intramolecular dynamics of vibrational levels (up to v = 5) of the ν1 mode in the (CF3)2CCO molecule that is induced by a multiphoton selective excitation of this mode by resonant femtosecond IR radiation has been studied. The times of intramolecular vibrational energy redistribution (IVR) from each vibrational level to remaining molecular modes have been determined. In accordance with theoretical predictions, a decrease in the IVR time with increasing quantum number v has been observed for the first time. A sharp decrease in the IVR time (down to 1.5 ps) at a wavelength of 2129 cm–1, corresponding to the v = 3 → v = 4 vibrational transition, is revealed. It has been shown that, with a negative chirp of a femtosecond radiation pulse, the population of high-lying vibrational levels of the ν1 mode increases significantly.