Temporal Dependence of Collisional Energy Transfer by Quasiclassical Trajectory Calculations of the Toluene-Argon System

Bernshtein, V.; Lim, Kieran F.; Oref, I.

doi:10.1021/j100013a024

Cited by 52 publications

(85 citation statements)

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“…Overall, most collisions tend to be short-lived and impulsive, consistent with our earlier QCT simulations of argon + toluene collisions. 13 There is insufficient time for equilibration of energy between the different degrees of freedom. Figure 3 plots the distribution of collision durations (as measured by the encounter number, En) for an argon bath gas at E' = 15 000, 30 000 and 41 000 cm -1 .…”

Section: Resultsmentioning

confidence: 99%

Quasiclassical trajectory calculations of collisional energy transfer in propane systems: Multiple direct-encounter hard-sphere model

Linhananta

Lim

2002

Phys. Chem. Chem. Phys.

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Quasiclassical trajectory calculations of collisional energy transfer from highly vibrationally excited propane + rare gas systems are reported. This work extends our hard-sphere model K.F. Lim, Phys. Chem. Chem. Phys., 2000, 2, 1385) to examine the variation of the internal energy during collisions with a rare bath gas. This was accomplished by recording the vibrational and rotational energy of propane after each atom-atom encounter during trajectory simulations of propane + rare gas systems. This provides detailed information of the energy flow during a collision. It was found that collisions with small number of encounters transfer energy efficiently, whereas those with many encounters do not. Detailed analyses reveal that the former collisions arise from trajectories with high initial impact parameter, whereas the latter has small initial impact parameter. The reason behind this is the dependence of collision energy transfer (CET) of large polyatomic molecules on its shape. This is connected to the well-known role of rotational energy transfer (RET) as a gateway for CET.

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Section: Resultsmentioning

confidence: 99%

Quasiclassical trajectory calculations of collisional energy transfer in propane systems: Multiple direct-encounter hard-sphere model

Linhananta

Lim

2002

Phys. Chem. Chem. Phys.

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“…[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.…”

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confidence: 99%

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

Ree

Kim

Shin

2013

Bulletin of the Korean Chemical Society

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Energy transfer and bond dissociation of C-Hmethyl and C-Hring in excited toluene in the collision with H2 and D2 have been studied by use of classical trajectory procedures at 300 K. Energy lost by the vibrationally excited toluene to the ground-state H2/D2 is not large, but the amount increases with increasing vibrational excitation from 5000 and 40,000 cm −1. The principal energy transfer pathway is vibration to translation (V-T) in both systems. The vibration to vibration (V-V) step is important in toluene + D2, but plays a minor role in toluene + H2. When the incident molecule is also vibrationally excited, toluene loses energy to D2, whereas it gains energy from H2 instead. The overall extent of energy loss is greater in toluene + D2 than that in toluene + H2. The different efficiency of the energy transfer pathways in two collisions is mainly due to the near-resonant condition between D2 and C-H vibrations. Collision-induced dissociation of C-Hmethyl and C-Hring bonds occurs when highly excited toluene (55,000-70,400 cm) interacts with the ground-state H2/D2. Dissociation probabilities are low (10) but increase exponentially with rising vibrational excitation. Intramolecular energy flow between the excited C-H bonds occurring on a subpicosecond timescale is responsible for the bond dissociation.

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“…From the variation of the energy curve in Figure 2b, we find that the collision begins at −1.45 ps and completes at −0.75 ps, so the duration of collision is 0.70 ps, which is close to 0.6 ps reported by Bernshtein and Oref in their trajectory calculations. 21 However, a sharp decrease in the vibrational energy over a short period, where the vibrational energy varies with two large amplitudes, indicates that the essential part of relaxation of the highly excited CH methyl is over within 0.2 ps, which is much shorter than the duration of collision. When both CH methyl and CH ring bonds are in highly excited states, the ensemble-averaged time scale for the relaxation of C-H methyl is 0.23 ps, 11 which is almost the same as the present case, that is, only the CH methyl vibration is highly excited, while the ring CH and all other modes are in their ground states.…”

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Collision-Induced Intramolecular Energy Flow in Highly Excited Toluene

2003

Bulletin of the Korean Chemical Society

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The collision-induced relaxation of vibrationally excited molecules has been the subject of continuing interest for the past several decades. [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. 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, which is much smaller than benzene derivatives such as hexafluorobenzene or other hydrocarbons such as toluene and azulene.5,12-14 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 . 14 These magnitudes are much larger in comparison to results for benzene colliding with argon. Among such large molecules, toluene is a particularly attractive molecule for studying collision-induced intramolecular energy flow and bond dissociation because of the presence of both methyl and ring CH bonds.In this paper, as an extension of th previous work in ref. 11, we study the collision-induced dynamics of highly vibrationally excited toluene interacting with argon using quasiclassical trajectory calculations. We now consider the collision system in which one CH (either CH methyl or CH ring ) vibration is in a highly excited state and the other in a ground state, while in Ref. 11 we considered both of CH methyl and CH ring bonds are in highly excited states. In the latter, it was not clear which CH bond is more effective for collisioninduced inter-and intra-molecular energy transfer in collision with Ar. Thus, we now elucidate which CH bond is more effective for collision-induced inter-and intra-molecular energy transfer, as considering and comparing the results of inter-and intra-molecular energy transfer dynamics when either CH methyl or CH ring is in highly excited states. Using the results obtained in the calculations, we discuss the relaxation of the excited CH vibration, and the time evolution of collision-induced intramolecular energy flow from the highly excited CH vibration. Thus, we elucidate the nature and mechanism of competition between methyl CH mode and ring CH mode in transferring energy to the incident atom. We set the initial vibrational energy of the methyl CH bond or the ring CH bond equal to the state just 0.10 eV below the dissociation threshold at 300 K. Interaction ModelThe present work follows the interaction model and numerical p...

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Temporal Dependence of Collisional Energy Transfer by Quasiclassical Trajectory Calculations of the Toluene-Argon System

Cited by 52 publications

References 11 publications

Quasiclassical trajectory calculations of collisional energy transfer in propane systems: Multiple direct-encounter hard-sphere model

Quasiclassical trajectory calculations of collisional energy transfer in propane systems: Multiple direct-encounter hard-sphere model

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

Collision-Induced Intramolecular Energy Flow in Highly Excited Toluene

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Temporal Dependence of Collisional Energy Transfer by Quasiclassical Trajectory Calculations of the Toluene-Argon System

Cited by 52 publications

References 11 publications

Quasiclassical trajectory calculations of collisional energy transfer in propane systems: Multiple direct-encounter hard-sphere model

Quasiclassical trajectory calculations of collisional energy transfer in propane systems: Multiple direct-encounter hard-sphere model

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

Collision-Induced Intramolecular Energy Flow in Highly Excited Toluene

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