Collision-Induced Intramolecular Energy Flow and CH Bond Dissociation in Excited Toluene

초록

The collision-induced intramolecular energy flow and CH bond dissociation in toluene has been studied using classical dynamics procedures. The molecule initially contains high amounts of internal excitation in the methyl CH and nearly benzilic CH stretches and is in interaction with Ar. The two CH stretches are coupled to each other through two CC stretching, two HCC bending, and one CCC bending, torsional, and wagging modes, all intermediary modes being in the ground state. At 300 K, the flow of vibrational energy between the two CH bonds, as well as energy transfer to or from Ar, is not efficient and the excitation initially stored in the CH vibration tends to remain in it with a small amount transferred to the nearby HCC bending. Even when the both CH bonds are initially excited to near the dissociation threshold, energy flow and in turn CH dissociation are not efficient at the room temperature condition. However, at the collision evergy much higher than the averae energy of the thermal condition, the benzilic CH bond tends to lose its initial excitation to the methyl CH stretch, resulting in a large probability of the methyl CH dissociation. The reaction time for the methyl CH dissociation is in the range of 0.5 ps to 0.7 ps.