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Titolo:
MICROCANONICAL TRANSITION-STATE THEORY RATE COEFFICIENTS FROM THERMALRATE CONSTANTS VIA INVERSE LAPLACE TRANSFORMATION
Autore:
VENKATESH PK; CARR RW; COHEN MH; DEAN AM;
Indirizzi:
EXXON RES & ENGN CO,CORP RES LABS,ROUTE 22 E ANNANDALE NJ 08801 EXXON RES & ENGN CO,CORP RES LABS ANNANDALE NJ 08801 UNIV MINNESOTA,DEPT CHEM ENGN & MAT SCI MINNEAPOLIS MN 55455
Titolo Testata:
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory
fascicolo: 42, volume: 102, anno: 1998,
pagine: 8104 - 8115
SICI:
1089-5639(1998)102:42<8104:MTTRCF>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Soggetto:
UNIMOLECULAR RATE THEORY; NUMERICAL INVERSION; DECOMPOSITION; RECOMBINATION; ETHYL;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
46
Recensione:
Indirizzi per estratti:
Citazione:
P.K. Venkatesh et al., "MICROCANONICAL TRANSITION-STATE THEORY RATE COEFFICIENTS FROM THERMALRATE CONSTANTS VIA INVERSE LAPLACE TRANSFORMATION", The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 102(42), 1998, pp. 8104-8115

Abstract

On the basis of concepts from the mathematical theory of approximation of functions, we propose a method of deriving microcanonical transition state theory rate coefficients, both as a function of the total energy and the total angular momentum, from thermal data, namely, the limiting high-pressure rate coefficients. The method does not require the knowledge of the frequencies and degeneracies of the transition state and is general in that it allows for non-Arrhenius forms of thermal data, but it only applies to reactions possessing an intrinsic energy barrier, It is shown that the derived microcanonical rate coefficient is almost identical to the computed Rice-Ramsperger-Kassel-Marcus (RRKM) microcanonical rate coefficient using explicit frequencies and degeneracies of the transition state, and furthermore, that the differencebetween the two is uniformly distributed over the entire range of total energy and the entire range of the total angular momentum. Comparison of the microcanonical coefficients from the proposed method with those from a standard nonvariational RRKM calculation is presented for the unimolecular decomposition of the ethyl radical and the unimolecular isomerization of methyl isocyanide. The agreement is shown to be excellent. A theoretical analysis of the fine structure of the microcanonical rate coefficient near the threshold of the reaction is enunicatedand the difficulty of extending the method to obtain variational microcanonical rate coefficients is described. We also, briefly, speculateon the possible merits of certain theoretical methods of analysis forcoping with the representation of thermal data, whose argument is thetemperature which is of semiinfinite range.

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Documento generato il 29/09/20 alle ore 13:13:56