A classical trajectory study of the photodissociation of T1 acetaldehyde: The transition from impulsive to statistical dynamics (2006)

View/ Open
Type of Content
Journal ArticlePublisher
AIP PublishingISSN
0021-96061089-7690
Language
engCollections
- Science: Journal Articles [1192]
Abstract
Previous experimental and theoretical studies of the radical dissociation channel of T1 acetaldehyde show conflicting behavior in the HCO and CH3 product distributions. To resolve these conflicts, a full-dimensional potential-energy surface for the dissociation of CH3CHO into HCO and CH3 fragments over the barrier on the T1 surface is developed based on RO-CCSDT/cc-pVTZDZ ab initio calculations. 20 000 classical trajectories are calculated on this surface at each of five initial excess energies, spanning the excitation energies used in previous experimental studies, and translational, vibrational, and rotational distributions of the radical products are determined. For excess energies near the dissociation threshold, both the HCO and CH3 products are vibrationally cold; there is a small amount of HCO rotational excitation and little CH3 rotational excitation, and the reaction energy is partitioned dominantly 90% at threshold into relative translational motion. Close to threshold the HCO and CH3 rotational distributions are symmetrically shaped, resembling a Gaussian function, in agreement with observed experimental HCO rotational distributions. As the excess energy increases the calculated HCO and CH3 rotational distributions are observed to change from a Gaussian shape at threshold to one more resembling a Boltzmann distribution, a behavior also seen by various experimental groups. Thus the distribution of energy in these rotational degrees of freedom is observed to change from nonstatistical to apparently statistical, as excess energy increases. As the energy above threshold increases all the internal and external degrees of freedom are observed to gain population at a similar rate, broadly consistent with equipartitioning of the available energy at the transition state. These observations generally support the practice of separating the reaction dynamics into two reservoirs: an impulsive reservoir, fed by the exit channel dynamics, and a statistical reservoir, supported by the random distribution of excess energy above the barrier. The HCO rotation, however, is favored by approximately a factor of 3 over the statistical prediction. Thus, at sufficiently high excess energies, although the HCO rotational distribution may be considered statistical, the partitioning of energy into HCO rotation is not.
Citation
Thompson KC, Crittenden DL, Kable SH, Jordan MJT (2006). A classical trajectory study of the photodissociation of T1 acetaldehyde: The transition from impulsive to statistical dynamics. The Journal of Chemical Physics. 124(4). 44302-.This citation is automatically generated and may be unreliable. Use as a guide only.
ANZSRC Fields of Research
34 - Chemical sciences::3407 - Theoretical and computational chemistry::340701 - Computational chemistry34 - Chemical sciences::3406 - Physical chemistry::340607 - Reaction kinetics and dynamics
Rights
All rights reserved unless otherwise statedRelated items
Showing items related by title, author, creator and subject.
-
Interpolated potential energy surfaces: How accurate do the second derivatives have to be?
Jordan MJT; Crittenden, Deborah (AIP Publishing, 2005)A global potential energy surface for the water dimer is constructed using the modified Shepard interpolation scheme of Collins et al. According to this interpolation scheme, the energy at an arbitrary geometry is expressed ... -
A Systematic CCSD(T) Study of Long-Range and Non-Covalent Interactions between Benzene and a Series of First and Second Row Hydrides and Rare Gas Atoms
Crittenden, Deborah (American Chemical Society (ACS), 2009)Binding energies, potential energy curves, and equilibrium intermonomer distances describing the interaction between benzene and a series of first - and second-row hydrides and rare gas atoms are calculated using coupled-cluster ... -
CASSCF-based explicit ligand field models clarify the ground state electronic structures of transition metal phthalocyanines (MPc; M = Mn, Fe, Co, Ni, Cu, Zn)
Wallace AJ; Crittenden, Deborah; Williamson, Bryce (Canadian Science Publishing, 2016)© 2016 Published by NRC Research Press. Multireference electronic structure methods are used to assign ground state electronic configurations for a series of metallophthalocyanines. Ligand orbital occupancies remain constant ...