Reformulation of the quasiequilibrium theory of ionic fragmentation

Klots, Cornelius E.

doi:10.1021/j100680a025

Cited by 293 publications

(89 citation statements)

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“…A useful variant of phase space theory if complex lifetimes are needed is based on a unimolecular decay theory of Klots [42]. The reaction is then considered to proceed via a capture cross section to form the intermediate complex which can then dissociate into all available reactant and product states consistent with conservation of energy and angular momentum.…”

Section: -P10mentioning

confidence: 99%

Theoretical approaches for studying Astrochemistry

Talbi

2011

EPJ Web of Conferences

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Section: -P10mentioning

confidence: 99%

Theoretical approaches for studying Astrochemistry

Talbi

2011

EPJ Web of Conferences

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“…The first one is the Rice-Ramsperger-Kassel-Marcus (RRKM) theory [1][2][3], which is practically identical with QET [4]. The second one, first proposed by Klots [13,14] but mainly developed by Ches-navich and Bowers in an impressive series of papers [15][16][17][18][19], is a variant of phase space theory that studies reactions involving very loose orbiting transition states (OTS). It is hereafter denoted OTST [1,3,10,[15][16][17][18][19][20][21][22].…”

Section: Of the Importance Of Studying Kerdsmentioning

confidence: 99%

Analysis of kinetic energy release distributions by the maximum entropy method

Leyh¹,

Gridelet²,

Locht³

et al. 2006

International Journal of Mass Spectrometry

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Energy is not always fully randomized in an activated molecule because of the existence of dynamical constraints. An analysis of kinetic energy release distributions (KERDs) of dissociation fragments by the maximum entropy method (MEM) provides information on the efficiency of the energy flow between the reaction coordinate and the remaining degrees of freedom during the fragmentation. For example, for barrierless cleavages, large translational energy releases are disfavoured while energy channeling into the rotational and vibrational degrees of freedom of the pair of fragments is increased with respect to a purely statistical partitioning. Hydrogen atom loss reactions provide an exception to this propensity rule. An ergodicity index, F, can be derived. It represents an upper bound to the ratio between two volumes of phase space: that effectively explored during the reaction and that in principle available at the internal energy E. The function F(E) has been found to initially decrease and to level off at high internal energies.For an atom loss reaction, the orbiting transition state version of phase space theory (OTST) is especially valid for low internal energies, low total angular momentum, large reduced mass of the pair of fragments, large rotational constant of the fragment ion, and large polarizability of the released atom. For barrierless dissociations, the major constraint that results from conservation of angular momentum is a propensity to confine the translational motion to a two-dimensional space. For high rotational quantum numbers, the influence of conservation of angular momentum cannot be separated from effects resulting from the curvature of the reaction path.The nonlinear relationship between the average translational energy and the internal energy E is determined by the density of vibrational-rotational states of the pair of fragments and also by non-statistical effects related to the incompleteness of phase space exploration.The MEM analysis of experimental KERDs suggests that many simple reactions can be described by the reaction path Hamiltonian (RPH) model and provides a criterion for the validity of this method.Chemically oriented problems can also be solved by this approach. A few examples are discussed: determination of branching ratios between competitive channels, reactions involving a reverse activation barrier, nonadiabatic mechanisms, and isolated state decay. Statistical methods in mass spectrometryFor the last 50 years, mass spectrometrists have made great efforts to rationalize fragmentation patterns and breakdown graphs by various statistical models that are all based on a common assumption. The internal energy deposited in a molecular ion is expected to be completely randomized before dissociation [1][2][3][4]. When this is the case, the reaction is declared ergodic.Equivalently, the energetically available phase space is said to be uniformly sampled within the lifetime of the molecular ion. In still more esoteric terms, the molecular ion is said to have reached a stat...

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“…Esta hipótesis fundamental es la base de una seria de teorías estadísticas como son las teorías RRK [18][19][20] , RRKM 42,43 , SACM [44][45][46][47][48][49] , y PST [50][51][52][53] . En muchas ocasiones estas teorías se usan para calcular las constantes de velocidad microcanónicas k(E), que es la magnitud de relevancia para las reacciones unimoleculares.…”

Section: Métodos Estadísticosunclassified

“…Para una explicación detallada acerca de cómo calcular P dir y P d t i s r el lector puede consultar la Ref. 53. Las constantes corregidas aparecen también recogidas en la Tabla 1 para una energía total de 110 kcal/mol.…”

Section: Nitrito De Metilounclassified

Dinámica de reacciones unimoleculares en fase gas: Desviaciones del comportamiento estadístico

Martı́nez-Núñez¹,

Vázquez²

2002

Quím. Nova

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Recebido em 26/3/01; aceito em 19/9/01 DYNAMICS OF UNIMOLECULAR REACTIONS IN GAS PHASE. DEVIATIONS FROM STATISTICAL BEHAVIOR. The present review summarizes the most relevant results of our research group obtained recently in the field of unimolecular reaction dynamics. The following processes are specifically analyzed: the isomerization, dissociation and elimination in methyl nitrite, the fragmentation reactions of the mercaptomethyl cation, the C-CO dissociation in the acetyl and propionyl radicals, and the decomposition of vinyl fluoride. In all the cases, only state-or energy-selected systems are considered. Special emphasis is paid to the possibility of systems exhibiting non-statistical behavior.

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Reformulation of the quasiequilibrium theory of ionic fragmentation

Cited by 293 publications

References 6 publications

Theoretical approaches for studying Astrochemistry

Theoretical approaches for studying Astrochemistry

Analysis of kinetic energy release distributions by the maximum entropy method

Dinámica de reacciones unimoleculares en fase gas: Desviaciones del comportamiento estadístico

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