Calculation of collisional-energy-transfer rates in highly excited molecules

Lim, Kieran F.; Gilbert, Robert G.

doi:10.1021/j100364a011

Cited by 72 publications

(59 citation statements)

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“…34,40 This cutoff between zero and non-zero opacity function defines the maximum impact parameter b m , and the trajectory cross-section σ traj (Equation (6) Inspection of Figure 1 indicates that every trajectory for b < ca. 0.4 nm, results in a "head-on" collision: the opacity function is unity, while for ca.…”

Section: Resultsmentioning

confidence: 99%

“…34 The LJ The change in rotational energy, <∆E R >, was calculated using the approximate rotational energy:…”

Section: Discussionmentioning

confidence: 99%

“…Following the notation of references 14,34 , B(E,J,E',J',l) is defined as the distribution of polyatomic substrate energies and angular momenta (E,J) after l encounters, where the initial microcanonical distribution is a delta function:…”

Section: Encounter Numbermentioning

confidence: 99%

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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%

“…34 The LJ The change in rotational energy, <∆E R >, was calculated using the approximate rotational energy:…”

Section: Discussionmentioning

confidence: 99%

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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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“…27 Complementing these studies have been ab initio or semiempirical calculations of the collisional energy transfer, frequently using classical mechanical trajectories for the collisions. [26][27][28][29][30][31][32][33][34][35][36] Analytical treatments of vibrational energy transfer have been given for particular cases. 5,[34][35][36][37][38] In particular, a detailed discussion of the original master equation and of its steady-state approximation is given by Penner and Forst,38 who expressed the solution in terms of hypergeometric functions.…”

Section: Introductionmentioning

confidence: 99%

“…A maximum impact parameter b max such that no trajectories lead to sizable energy transfer for b Ͼ b max has usually been imposed in the literature to avoid this peak. [26][27][28][29][30][31][32][33][34][35] Then a single exponential, step-ladder or biexponential model was usually adopted to fit the trajectory data. For example, Brown and Miller 26 neglected the bin in which EЈ − E Ϸ 0 with a bin size of around 30 cm −1 in a biexponential fit to the trajectory data.…”

Section: Introductionmentioning

confidence: 99%

On collisional energy transfer in recombination and dissociation reactions: A Wiener–Hopf problem and the effect of a near elastic peak

Zhu

Marcus

2008

The Journal of Chemical Physics

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The effect of the large impact parameter near-elastic peak of collisional energy transfer for unimolecular dissociation/bimolecular recombination reactions is studied. To this end, the conventional single exponential model, a biexponential model that fits the literature classical trajectory data better, a model with a singularity at zero energy transfer, and the most realistic model, a model with a near-singularity, are fitted to the trajectory data in the literature. The typical effect of the energy transfer on the recombination rate constant is maximal at low pressures and this region is the one studied here. The distribution function for the limiting dissociation rate constant k 0 at low pressures is shown to obey a Wiener-Hopf integral equation and is solved analytically for the first two models and perturbatively for the other two. For the single exponential model, this method yields the trial solution of Troe. The results are applied to the dissociation of O 3 in the presence of argon, for which classical mechanical trajectory data are available. The k 0 's for various models are calculated and compared, the value for the near-singularity model being about ten times larger than that for the first two models. This trend reflects the contribution to the cross section from collisions with larger impact parameter. In the present study of the near-singularity model, it is found that k 0 is not sensitive to reasonable values for the lower bound. Energy transfer values ͗⌬E͘'s are also calculated and compared and can be similarly understood. However, unlike the k 0 values, they are sensitive to the lower bound, and so any comparison of a classical trajectory analysis for ͗⌬E͘'s with the kinetic experimental data needs particular care.

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Trajectory studies on the collisional relaxation of highly excited benzenes by mono‐ and polyatomic colliders

Lenzer

Luther

1997

Ber Bunsenges Phys Chem

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Collisional energy transfer (CET) of highly vibrationally excited benzene and hexafluorobenzene molecules has been investigated by quasiclassical trajectory calculations. Influences of the intramolecular potential reflected in molecular parameters are studied systematically in collisions with argon. It is found that the lower the vibrational frequencies the more efficient is CET. Intermolecular potential effects are investigated. At larger well depths (for benzene+argon) the first moment of energy transfer <ΔE> scales with ε and is not very sensitive to details of the interaction. However at small well depths ε (for benzene + helium) energy transfer is dominated by the exact shape of the intermolecular potential, especially of the repulsive part. Benzene‐benzene collisions are studied as an example for CET between polyatomics and large colliders. Excellent quantitative agreement with experiment is found for <ΔE> and its energy dependence. The results suggest that vibrational energy loss of the excited molecule is dominated by V‐V transfer and that the rotation is heated up more strongly with increasing ε, an effect also present for noble gas colliders.

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Calculation of collisional-energy-transfer rates in highly excited molecules

Cited by 72 publications

References 0 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

On collisional energy transfer in recombination and dissociation reactions: A Wiener–Hopf problem and the effect of a near elastic peak

Trajectory studies on the collisional relaxation of highly excited benzenes by mono‐ and polyatomic colliders

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