Abstract
Intramolecular dynamics of the vibrational levels (up to v = 5) of the ν 1 mode in (CF 3 ) 2 CCO molecule, induced via multiphoton selective excitation of this mode by resonant femtosecond IR radiation, was studied. The times of intramolecular vibrational energy redistribution ( IVR ) of each vibrational level v to the remaining modes of the molecule were measured. In accordance with the theory predictions the decrease of IVR time with increasing v is observed. A sharp reduction of the IVR time (up to 1 ps) at a wavelength of 2130 cm −1 of transition v=3 → v=4 was found. It was shown that with a negative chirp of a femtosecond radiation pulse the population of high-lying vibrational levels of ν 1 modes significantly increases.
Highlights
At a multiphoton excitation of selected vibrational modes in the molecule an implementation of photochemical bond-selective processes is possible
The experiments confirmed a selective excitation of the resonant mode ν1 up to vibrational level v = 5, which was previously registered by another way [2]
As the level of vibrational excitation of the resonant mode grows up the exponential decrease of the ΔOD signal was observed with characteristic times from W = 6 ps for the transitions 0 1 and 1 2 to W = 3.5 ps for the transitions 4 5 and 5 6
Summary
At a multiphoton excitation of selected vibrational modes in the molecule an implementation of photochemical bond-selective processes (or group of bonds) is possible. In the experiments the IR pump-probe method with a spectral analysis of the probing radiation was used. For this purpose the new IR detector, namely high-sensitive and lownoise linear array on the basis of CdHgTe, developed with the participation of the authors, was employed for the first time.
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