Trajectory simulations of collisional energy transfer in highly excited benzene and hexafluorobenzene

Abstract

A quasiclassical trajectory study of energy transfer in benzene-benzene collisions A classical trajectory study of collisional energy transfer in thermal unimolecular reactions Quasiclassical trajectory calculations of the energy transfer of highly vibrationally excited benzene and hexafluorobenzene ͑HFB͒ molecules colliding with helium, argon and xenon have been performed. Deactivation is found to be more efficient for HFB in accord with experiment. This effect is due to the greater number of low frequency vibrational modes in HFB. A correlation between the energy transfer parameters and the properties of the intramolecular potential is found. For benzene and HFB, average energies transferred per collision in the given energy range increase with energy. Besides weak collisions, more efficient ''supercollisions'' are also observed for all substrate-bath gas pairs. The histograms for vibrational energy transfer can be fitted by biexponential transition probabilities. Rotational energy transfer reveals similar trends for benzene and HFB. Cooling of rotationally hot ensembles is very efficient for both molecules. During the deactivation, the initially thermal rotational distribution heats up more strongly for argon or xenon as a collider, than for helium, leading to a quasi-steady-state in rotational energy after only a few collisions.

Collision-induced Energy Transfer and Bond Dissociation in Toluene by H2/D2

“…[23][24][25][26][27][28][29][30][31] One such molecule is toluene, which contains two distinctly different C-H bonds, namely the methyl C-H and ring C-H bonds, along with many C-C bonds. When toluene undergoes a collision with other molecules, both intermolecular energy transfer and intramolecular energy flow from one CH bond to others via C-C bonds can occur.…”

Collision-Induced Intramolecular Energy Flow in Highly Excited Toluene

“…The average energy transfer per collision between the highly vibrationally excited benzene and a noble gas atom is known to be about 30 cm −1 , which is much smaller than benzene derivatives such as hexafluorobenzene or other hydrocarbons such as toluene and azulene. 5,[12][13][14] For example, for hexafluorobenzene + Ar, the measured value of the mean energy transfer per collision by the ultraviolet absorption method is −330 cm −1 , 13 whereas the calculated value using quasiclassical trajectory methods at 300 K is −150 cm −1 . 5 For toluene + Ar, the amount of energy transfer is about −200 cm −1 .…”

“…5,[12][13][14] For example, for hexafluorobenzene + Ar, the measured value of the mean energy transfer per collision by the ultraviolet absorption method is −330 cm −1 , 13 whereas the calculated value using quasiclassical trajectory methods at 300 K is −150 cm −1 . 5 For toluene + Ar, the amount of energy transfer is about −200 cm −1 . 14 These magnitudes are much larger in comparison to results for benzene colliding with argon.…”

“…In particular, molecules vibrationally excited to near their dissociation threshold can undergo bond dissociation and vibrational relaxation, processes that play an important role in reaction dynamics. Recent studies 3,[5][6][7][8][9][10][11] show that when the excited molecule is a large organic molecule, the average amount of energy transfer per collision is not very large. The average energy transfer per collision between the highly vibrationally excited benzene and a noble gas atom is known to be about 30 cm −1 , which is much smaller than benzene derivatives such as hexafluorobenzene or other hydrocarbons such as toluene and azulene.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] In recent years, furthermore, collisions involving large molecules have been studied actively, revealing valuable information on the rates and the mechanisms of vibrational energy processes. In particular, molecules vibrationally excited to near their dissociation threshold can undergo bond dissociation and vibrational relaxation, processes that play an important role in reaction dynamics.…”