Reference : How ergodic is the fragmentation of the pyridine cation? A maximum entropy analysis
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
How ergodic is the fragmentation of the pyridine cation? A maximum entropy analysis
[fr] Dans quelle mesure la fragmentation de la pyridine ionisée est-elle ergodique ? Une analyse par la méthode du maximum d'entropie
Gridelet, E. [> > > >]
Locht, Robert mailto [Université de Liège - ULg > Département de Chimie > Laboratoire de Dynamique Moléculaire (Sciences) >]
Lorquet, Andrée mailto [Université de Liège - ULg > Département de chimie (sciences) > Laboratoire de dynamique moléculaire > >]
Lorquet, Jean-Claude mailto [Université de Liège - ULg > Département de Chimie (Faculté des sciences) > Laboratoire de Dynamique Moléculaire (Sciences) > >]
Leyh, Bernard mailto [Université de Liège - ULg > > Laboratoire de Dynamique Moléculaire >]
International Journal of Mass Spectrometry
Elsevier Science Bv
Special Issue in honour of Helmut Schwarz
Yes (verified by ORBi)
[en] kinetic energy release ; maximum entropy method ; phase space ; pyridine ion ; C4H4+ ion ; statistical theory
[en] The kinetic energy released to the C4H4+ and HCN fragments produced by the dissociation of the pyridine ion has been determined by a retarding field technique up to an internal energy of 4eV above the reaction threshold. This extends our previous study limited to the metastable domain [Int. J. Mass Spectrom. Ion Process. 185/186/187 (1999) 155]. Retarding potential curves resulting from dissociative photoionization using the He(I), Ne(I), and Ar(II) resonance lines have been analyzed by the maximum entropy method. The comparison between the experimentally measured curves and those calculated for the prior (i.e., most statistical) situation reveals the existence of dynamical constraints that prevent phase space from being fully explored. The "ergodicity index" F(E) that measures the efficiency of phase space sampling as a function of the internal energy E of the molecular ion is found to decrease steadily as a function of E and to level off at a value of about 50% when E greater than or equal to 2.5 eV At these high internal energies where phase space exploration no longer decreases, spontaneous intramolecular vibrational energy redistribution (i.e., resulting from the anharmonicity of the molecular vibrations) is thought to contribute to internal energy randomization to a limited extent only. When the lifetime is short, phase space exploration is believed to result instead from the relaxation of the electronic energy via a cascade of non-radiative transitions, which leads to a great diversity of initial conditions, and thus, contributes to statisticity. (C) 2003 Elsevier Science B.V. All rights reserved.
Laboratoire de Dynamique Moléculaire
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