Monte Carlo Calculations. IV. Further Studies of Unimolecular Dissociation

Bunker, Don L.

doi:10.1063/1.1725427

Cited by 186 publications

(70 citation statements)

References 21 publications

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“…The propylene arose as a decomposition product in reaction 3 and from the photolysis of ketene; in view of its dual origin it, also, was not a useful monitor of reaction path [3] or reaction path [4]. The ratio of ( D I / D~~) is plotted in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Intramolecular vibrational energy relaxation. Decomposition of chemically activated alkylcyclobutanes

Wang¹,

Rabinovitch²

1976

Can. J. Chem.

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FA-MEI WANG and B. S. RABINOVITCH. Can. J. Chem. 54, 943 (1976). This paper describes an approach to the study of intramolecular energy relaxation of highly vibrationally excited complex molecules. The features of the decomposition of a series of chemically activated alkylcyclobutanes are outlined, including variable selectivity of the initial, non-randomized state of excitation. It is shown how this can afford both a qualitative test of the postulate of internal energy randomization employed in the Rice-Ramsperger-Kassel-Marcus treatment of unimolecular reactions, as well as a quantitative measure of the rate of relaxation. The study of the first members of this series, ethyl and dimethyl cyclobutane, is described. As expected, the first members can provide a lower limit to'the relaxation rate, namely, X > 1012 s-1.

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Section: Resultsmentioning

confidence: 99%

“…The differential nature of intramolecular vibrational energy relaxation in this system should, in principle, be perceptible by monitoring the relative amounts of butenes produced via reaction paths [2], [3], and [4], as a function of pressure.…”

Section: Resultsmentioning

confidence: 99%

Intramolecular vibrational energy relaxation. Decomposition of chemically activated alkylcyclobutanes

Wang¹,

Rabinovitch²

1976

Can. J. Chem.

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“…The ®rst such comparisons can be attributed to Bunker's work on unimolecular reactions [17,18]. Karplus and coworkers [19±21] performed the ®rst comparisons for bimolecular reactions.…”

Section: Accuracy Of the Fundamental Assumption Of Tstmentioning

confidence: 99%

Perspective on "The transition state method"

Garrett

2000

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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A perspective is provided on Wigner's classic paper on transition-state theory (TST). After providing a brief review of the historical context of this work, we review its key contributions including Wigner's dynamical perspective on TST, the fundamental assumption of TST, and the upper-bound property of classical TST. A discussion is also presented of subsequent progress in the ®eld, which was stimulated by this work. This progress includes the following:1. Demonstrations of the validity of the fundamental assumption for classical systems. Further investigations into the classical foundationsof TST that helped elucidate relationships between classical trajectories and TST. 3. The development of a variational form of the theory. 4. The development of variational TST into a quantitative tool for predicting rate constants. 5. The search for an``exact'' quantum mechanical version of TST. 6. The development of TST-like expressions for the exact quantum mechanical rate constant. 7. The extension of TST to reactions in condensed phases.

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“…Implicit in (a) is the requirement that the vibrational modes be strictly harmonic or that, at least, the rate of intramolecular energy transfer be small compared to k(qo). The success of the RRKM theory indicates, however, that the reverse situation is normally the case [12]. Following ~olc [10], k(qo) in (4) must be averaged over all possible energies in each mode (from 0 to %, the total vibrational energy) consistent with energy conservation.…”

Section: Introductionmentioning

confidence: 98%

Product translational energy distributions from the harmonic model for unimolecular decomposition

Safron

1975

Molecular Physics

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To cite this article: S.A. Safron (1975) Product translational energy distributions from the harmonic model for unimolecular decomposition, Formulae for the distribution of relative translational energy of products from decomposition of collision complexes are derived from the Slater model of unimolecular rate theory. The development presented parallels the statistical transition state theory (RRKM) approach. Although a similar form of the energy distribution is found, the identical result is obtained in the classical limit only for the special case of a 'loose' complex configuration at the critical point. INTRODUCTIONThe translational energy distribution of unimolecular decomposition products reflects as much about the dynamical structure of the fragmenting molecule as does the better known angular distribution [1-3]. The great majority of reactions involving long-lived collision complexes have been found to correlate well with the simple predictions of the transition state model (TSM), based on the statistical Rice-Ramsperger-Kassel-Marcus (RRKM) theory for unimolecular decomposition [4,5]. In its present formulation the TSM treats the decomposition as that of a ' loose ' complex with the critical point at the top of the centrifugal barrier, which has been shown to be equivalent to the phasespace model of Light and co-workers [6,7]. Recent molecular beam experiments [2], however, show that there are important reactions which proceed via complex formation that do not conform to the TSM. The present indication is that while the basic statistical RRKM approach may be appropriate, structural features of a ' tight ' complex have yet to be properly incorporated [8,5].In this paper an harmonic model (HM) for the translational energy distribution of the fragments is developed in terms of the Slater model for unimolecular decomposition [9], paralleling the development of the TSM in [4]. Energy randomization among the vibrational modes due to anharmonicity is treated in the sense of Solc [10] ; that is (as in the RRKM treatment), anharmonicity is recognized as the mechanism for intramolecular energy transfer which is rapid compared to the complex dissociation rate, but the harmonic nature of the vibrational modes is not otherwise affected. Because the HM is a thoroughly classical model, it can never be viable in the sense of the TSM; yet, it can suggest possible modifications of the TSM for ' tight ' complexes. Slater [11] has shown that when all vibrations participate in energy randomization, the classical form of the RRKM rate constant is obtained. However, the classical Downloaded by [Michigan State University] at

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Monte Carlo Calculations. IV. Further Studies of Unimolecular Dissociation

Cited by 186 publications

References 21 publications

Intramolecular vibrational energy relaxation. Decomposition of chemically activated alkylcyclobutanes

Intramolecular vibrational energy relaxation. Decomposition of chemically activated alkylcyclobutanes

Perspective on "The transition state method"

Product translational energy distributions from the harmonic model for unimolecular decomposition

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