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

Abstract

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.

Ultrafast Transient Vibrational Action Spectroscopy of Cryogenically Cooled Ions

“…Vibrational dynamics are also limited to the tag-loss timescale, which depends on the coupling strength between the ion's vibrational modes and the low-frequency ion-tag intermolecular mode. Tag-loss timescales are expected on the tens of picoseconds to nanosecond timescale, [37][38][39] therefore, interesting vibrational dynamics should still be accessible using the tag-loss method. One intriguing possibility is to measure rotational reorientation dynamics as a method to elucidating the structures of large molecular systems.…”

Observing Intramolecular Vibrational Energy Redistribution via the Short-Time Fourier Transform

“…In 1982, Smalley wrote “Intramolecular vibrational randomization (IVR) processes, and their rate, and their degree of completeness have traditionally ranked high among the prime intellectual issues of chemical kinetics,” and he gave 222 references . IVR also denotes intramolecular vibrational (energy) redistribution − and intramolecular vibrational relaxation, − and it is also called intermode energy flow, intramolecular energy flow, and intramolecular energy transfer; we treat all of these terms as synonyms. The process of IVR is hard to study in highly excited molecules due to the anharmonic breakdown of the normal mode picture.…”