Trajectory Study Of Energy Transfer Research Articles

Trajectory study of energy transfer and unimolecular dissociation of highly excited allyl with argon.

The influence of rotational excitation on energy transfer in single collisions of allyl with argon and on allyl dissociation is investigated. About 90,000 classical scattering simulations are performed in order to determine collision-induced changes in internal energy and in allyl rotational angular momentum. Dissociation is studied by means of about 50,000 additional trajectories evolved for the isolated allyl under three different conditions: allyl with no angular momentum (J = 0); allyl with the same microcanonically sampled initial conditions used for the collisions (J*); allyl evolving from the corresponding exit conditions after the collision. The potential energy surface is the sum of an intramolecular potential and an interaction one, and it has already been used in a previous work on allyl-argon scattering (Conte, R.; Houston, P. L.; Bowman, J. M. J. Phys. Chem. A 2013, 117, 14028-14041). Energy transfer data show that increased initial rotation favors, on average, increased relaxation of the excited molecule. The availability of a high-level intramolecular potential energy surface permits us to study the dependence of energy transfer on the type of starting allyl isomer. A turning point analysis is presented, and highly efficient collisions are detected. Collision-induced variations in the allyl rotational angular momentum may be quite large and are found to be distributed according to three regimes. The roles of rotational angular momentum, collision, and type of isomer on allyl unimolecular dissociation are considered by looking at dissociations times, kinetic energies of the fragments, and branching ratios. Generally, rotational angular momentum has a strong influence on the dissociation dynamics, while the single collision and the type of starting isomer are less influential.

Classical Trajectory Study of Energy Transfer in Collisions of Highly Excited Allyl Radical with Argon

Predicting the results of collisions of polyatomic molecules with a bath of atoms is a research area that has attracted substantial interest in both experimental and theoretical chemistry. Energy transfer, which is the consequence of such collisions, plays an important role in gas-phase kinetics and relaxation of excited molecules. We present a study of energy transfer in single collisions of highly vibrationally excited allyl radical in argon. We evolve a total of 52 000 classical trajectories on a potential energy surface, which is the sum of an ab initio intramolecular potential for the allyl and a pairwise interaction potential describing the argon's effect on the allyl. The former is described by means of a permutationally invariant full-dimensional potential, whereas the interaction potential between allyl and argon is obtained by means of a sum of pairwise potentials dependent on nonlinear parameters that have been fit to a set of MP2/avtz counterpoise corrected ab initio energies. Results are reported for energy transfers and related probability densities at different collisional energies. The sensitivity of results to the interaction potential is considered and the potential is shown to be suitable for future applications involving different isomers of the allyl. The impact of highly efficient collisions in the energy transfer process is examined.

Classical Trajectory Study of Energy Transfer in Pyrazine−CO Collisions

Classical trajectory calculations for collisions between vibrationally hot pyrazine (E = 40332 cm-1) and room-temperature CO are compared with recent diode laser experiments. Ab initio calculations were carried out to determine parameters for the pairwise Lennard-Jones intermolecular potential. The trajectory results appear to show good qualitative agreement with preliminary experimental results. The highest ΔE collisions occur when the CO happens to lie above the pyrazine plane just as the underlying CH wag executes an unusually high amplitude motion. Artificially doubling the length of the CO produces results for the angular momentum transfer to the CO molecule that look quite similar to those for angular momentum transfer to CO2 in analogous pyrazine−CO2 experiments.

A quasiclassical trajectory study of energy transfer in benzene–benzene collisions

Collisional energy transfer from large, highly vibrationally excited molecules has been studied by quasiclassical trajectory calculations and results for large polyatomic colliders are reported for the first time. Highly excited benzene molecules in a thermal bath gas of benzene were investigated using a sum of atom–atom Lennard-Jones interactions for the intermolecular potential. Excellent agreement with experiment has been found for the first moment of energy transfer 〈ΔE〉 and its energy dependence. 〈ΔE〉 is increasing with a slight leveling off at high energies. The results suggest that vibrational energy loss of the excited molecule is dominated by V–V transfer.

Classical trajectory study of energy transfer between argon atoms and vibrationally-rotationally excited ozone molecules

Classical trajectory study of energy transfer between argon atoms and vibrationally-rotationally excited ozone molecules

Classical trajectory studies of energy transfer in Ar–difluorodiazirine collisions

We report the results of extensive classical trajectory studies of energy transfer in Ar–difluorodiazirine (DFD) collisions. The use of classical mechanics for this purpose leads to some difficulties of interpretation; these are discussed. In the conclusions drawn from the calculations, emphasis is placed on the qualitative results, and no attempt is made to estimate collision cross sections or transition probabilities. The most important results to emerge from our calculations are the following: (i) Classical mechanical simulations of Ar–DFD collisions lead to the conclusion that the induced mode-to-mode energy transfer is very selective, just as is observed. (ii) Despite thermal averaging, some idiosyncratic features of the potential energy surface are reflected in the average energy transfers due to collision (e.g., in the impact parameter dependence of the root-mean-square rotational energy change on collision). (iii) The branching pattern characteristic of collision induced mode-to-mode vibrational energy transfer is likely sensitive to details of the potential energy surface, and not just to its overall structure. We reach this conclusion because the particular pathways of collision induced mode-to-mode energy transfer in the Ar–1B1 DFD system are not correctly reproduced by our calculations, despite the correct prediction of selectivity in mode-to-mode energy transfer.

A Monte Carlo quasiclassical trajectory study of energy transfer in Ar+HF collisions

Quasiclassical trajectories on a pairwise-additive potential-energy surface have been used to compute state-to-state cross sections for energy transfer in Ar+HF. Interest is focused upon relaxation from high vibration-rotation states. Pure-rotational energy transfer in excited vibrational states, vibrational relaxation, and the effect of relative translational energy on the energy transfer were also investigated. Most of the calculations were carried out for 1.0 eV relative translational energy. Initial vibrational states vi = 0, 2, 4, and 6 and initial rotational states Ji = 0, 10, 20, 30, and 40 were studied at this collision energy. The energy transfer for initial state vi = 4, Ji = 20 was studied at the initial relative translational energies 0.2, 0.4, 0.6, 0.8, and 1.0 eV. For collisions of Ar with highly excited HF the dominant energy transfer is V-R. The energy transfer results in an increase in the rotational state for downward vibrational transitions and a decrease in rotational state for upward vibrational transitions. The results suggest that pure-rotational energy transfer for low levels of rotational energy (Ji≲10), even in high vibrational states, should be accurately described by the rigid-rotor approximation. None of the energy transfer processes has a strong dependence on the initial relative translation energy, however, the influence is not negligible in all cases.

Erratum: On a classical trajectory study of energy transfer in some atom–diatomic molecule systems [J. Chem. Phys. 56, 3570 (1972)

Erratum: On a classical trajectory study of energy transfer in some atom–diatomic molecule systems [J. Chem. Phys. 56, 3570 (1972)

Trajectory studies of energy transfer: CH 3NC with He, Xe, H 2 and N 2

A trajectory program was used to simulate the collisions of CH 3NC with He, Xe, H 2 and N 2. Calculated energy transfer is in accord with experiment. The pattern of CH 3NC vibrational mode energization is found to be noticeably non-random. The approximate sampling methods used in thermal unimolecular trajectory studies produce a more uniform state distribution.

On a Classical Trajectory Study of Energy Transfer in Some Atom-Diatomic Molecule Systems

Atom-diatomic molecule energy transfer has been studied using classical trajectories. The main objective was to evaluate the effects of initial vibrational, rotational, and translational energy on energy transfer so that some understanding of the dynamical mechanism of energy transfer in these systems could be obtained. The four collision systems studied are H2+I, H2+Cl, HCl+H, and HCl+Cl. The initial states of these three-dimensional trajectories were chosen in accordance with quantum rules. The potential-energy surfaces employed in the calculation were of the semiempirical VB formalism. The H-atom exchange reaction Cl′ + HCl′′ → HCl′ + Cl′′ was shown to be a contributor in the relaxation of vibrationally excited HCl molecules.