A direct comparison of vibrational deactivation of hexafluorobenzene excited by infrared multiple photon absorption and internal conversion

Abstract

We report the first direct comparison between energy transfer parameters measured using infrared multiphoton absorption ͑IRMPA͒ versus ultraviolet ͑UV͒ excitation followed by rapid internal conversion ͑IC͒. Highly excited hexafluorobenzene ͑HFB͒ molecules in the electronic ground state were prepared by ͑i͒ IRMPA by CO 2 laser pumping to an average initial energy of 14 500-17 500 cm Ϫ1 and ͑ii͒ UV excitation to ϳ40 300 cm Ϫ1 followed by IC. The vibrational deactivation of the highly excited HFB by the monatomic collider gas argon was monitored by time-resolved infrared fluorescence. The results for the two methods are identical within experimental error, demonstrating the viability of IRMPA as a method of state preparation for vibrational deactivation experiments involving large molecules.

Vibrational Energy Transfer Modeling of Nonequilibrium Polyatomic Reaction Systems

“…However, the vibrational energy distributions produced by IRMPA are difficult to characterize in detail. Recently, the first direct comparison between energy transfer parameters measured with IRMPA versus the standard IRF technique was carried out , using hexafluorobenzene, which has also been studied using the UVA method. , For deactivation by the series of noble gas colliders, the average energy transferred per collision was found to be essentially a linear function of energy and indistinguishable from the IRF results. This result gives confidence that the IRMPA method will produce good results in future studies.…”

Chemical Dynamics Simulations of Energy Transfer for Propylbenzene Cation and He Collisions

“…Collisional intermolecular energy transfer (IET) has been widely studied for many years − and is particularly important for modeling unimolecular reactions. − There have been a number of studies of IET for neutral molecule and ions, including those for azulene, − benzene, − toluene-d 0 and -d 8 , − hexafluorobenzene, , pyrazine, − cycloheptatriene, SF 6 – anion, and the ethylbenzene, , propylbenzene, and butylbenzene cations.…”

“…Collisional intermolecular energy transfer (IET) has been widely studied for many years 1−4 and is particularly important for modeling unimolecular reactions. 5−7 There have been a number of studies of IET for neutral molecule and ions, including those for azulene, 8−14 benzene, 15−18 toluene-d 0 and -d 8 , 19−21 hexafluorobenzene, 22,23 pyrazine, 24−31 cycloheptatriene, 32 SF 6 − anion, 33 and the ethylbenzene, 34,35 propylbenzene, 36 and butylbenzene 37 cations. In previous experiments 34−37 the charge transfer reaction between an alkylbenzene molecule and O 2 + , in a turbulent ion flow tube (TIFT), was used to prepare vibrationally excited ethyl-, propyl-and butylbenzene cations. In these studies, the competition between collisional stabilization and dissociation of the excited alkylbenzene cation was studied.…”

Chemical Dynamics Simulation of Energy Transfer: Propylbenzene Cation and N2 Collisions

“…Understanding the dynamics of collisional energy transfer is very important. 5−7 For this reason, there have been many experimental studies of collisional IET for numerous molecules such as benzene, 8−11 toluene, 12−14 azulene, 15−21 hexafluorobenzene, 22,23 cycloheptatriene, 24 pyrazine, 25−32 and alkylbenzene cation. 33−36 Moreover, theoretical and computational studies have been performed for collisional IET of vibrationally excited molecules, including CS 2 , 37−39 SO 2 , 39 benzene, 40−43 toluene, 44,45 hexafluorobenzene, 43,46−48 azulene, 49−55 and propylbenzene cation.…”

“…Collisional intermolecular energy transfer (IET) between a highly vibrationally excited molecule and bath molecules has been widely studied − to model unimolecular reactions. Understanding the dynamics of collisional energy transfer is very important. − For this reason, there have been many experimental studies of collisional IET for numerous molecules such as benzene, − toluene, − azulene, − hexafluorobenzene, , cycloheptatriene, pyrazine, − and alkylbenzene cation. − Moreover, theoretical and computational studies have been performed for collisional IET of vibrationally excited molecules, including CS 2 , − SO 2 , benzene, − toluene, , hexafluorobenzene, ,− azulene, − and propylbenzene cation . In modeling experiments, it is important to understand the efficiency of collisional IET for different bath molecules.…”