Dynamics of vibrational energy transfer in polyatomic molecules. A model calculation

Tzidoni, E.; Oref, I.

doi:10.1016/0301-0104(84)85189-7

Cited by 7 publications

(1 citation statement)

References 48 publications

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“…Solution of Collisional Energy Transfer Master Equation. The details of the solution of the master equation, eq 3, are given in refs and . Briefly, the master equation is cast into a matrix form where F̄ represents the population vector and H is a n × n matrix whose elements are the transition probabilities and the RRKM theory rate coefficients which appear in equation 3.…”

Section: Theorymentioning

confidence: 99%

Energy Transfer Rate Coefficients from Trajectory Calculations and Contributions of Supercollisions to Reactive Rate Coefficients

1996

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Quasiclassical trajectory calculations on the CS 2 -CO system were performed. Analytical biexponential functions were fit to the trajectory results, and energy-dependent energy transfer transition probability functions and rate coefficients were derived. They, in turn, were used in solutions of master equations. Unimolecular rate coefficients for cyclobutane fission and cyclobutene isomerization in Ar bath gas at various temperatures were obtained. Supercollisions, collisions which transfer more than 5 times the average energy transferred in a down collision, were found to contribute to the high-energy tail of the biexponential transition probability function. To assess their contribution to the unimolecular rate coefficients, their values which were obtained from trajectory-based double-exponential transition probabilities are compared with those obtained from singleexponential weak-collision transition probabilities. For cyclobutane fission an ∼5-fold increase in the value of the rate coefficient is found at 1000 K and ∼7-fold increase at 1500 K when the biexponential function is used. For cyclobutene isomerization the change ranges from an ∼7-fold increase at 500 K to an ∼9-fold increase at 1500 K. Since the magnitude of supercollisions and, thus, the magnitude of the tail of the probability distribution can vary depending on the system, a systematic study was performed on how the high-energy tail affects the values of the unimolecular rate coefficients. It was found that for weighing factors of the strongcollision contribution to the biexponential probability function of 0.5% or 10% of that of the weak-collision contribution (with an exponential parameter of 300 cm -1 ) the rate coefficient increases with the size of the strong-collision exponent and with temperature. When the contribution of the weak-collision exponent to the energy transfer probability function was artificially removed, it was found that in some cases, 0.5% of the strong-collision part contributes ∼70% to the overall rate coefficient while 99.5% of the weak-collision part contributes only 30%.

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Section: Theorymentioning

confidence: 99%