Reference : NONADIABATIC UNIMOLECULAR REACTIONS .2. ISOTOPE EFFECTS ON THE KINETIC-ENERGY RELEASE
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
http://hdl.handle.net/2268/3997
NONADIABATIC UNIMOLECULAR REACTIONS .2. ISOTOPE EFFECTS ON THE KINETIC-ENERGY RELEASE
English
Remacle, Françoise mailto [Université de Liège - ULg > Département de chimie (sciences) > Laboratoire de chimie physique théorique >]
Dehareng, Dominique mailto [Université de Liège - ULg > > Centre d'ingénierie des protéines >]
Lorquet, Jean-Claude mailto [Université de Liège - ULg > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences) >]
1988
Journal of Physical Chemistry
American Chemical Society
92
16
4784-4787
Yes (verified by ORBi)
International
0022-3654
Washington
DC
[en] nonadiabatic coupling ; isotope effects ; HOCO and DOCO cations
[fr] statistical rate constant ; ab initio calculations
[en] This paper investigates the isotope effect that occurs when XOCO+ ions dissociate into XOC+ + 0 on a microsecond time scale (X = H or D). The reaction mechanism involves an electronic spin-forbidden predissociation between a stable singlet state and a repulsive triplet. Application of the statistical equations developed in the previous paper shows that, at a given energy, the predissociation rate constant is consistently smaller for DOCO’ than for HOCO+. Therefore, the internal energy necessary to bring about dissociation of the hydrogenated compound with a given rate constant is always lower than that of the deuteriated compound by a quantity AE* which is found to be equal to ca. 0.050 eV when k = lo6 s-l and to ca 0.020 eV for k = lo3 s-1. As a result, the excess energy which is released as kinetic energy carried by the fragments is substantially greater for the deuteriated than for the hydrogenated compound. This accounts for experiments which indicate that, in the microsecond time scale, DOCO’ gives rise to a dished metastable peak whereas the corresponding signal for HOCO’ is simply Gaussian.
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS ; Fonds de la Recherche Fondamentale Collective d’Initiative des Chercheurs - FRFC ; Politique Scientifique Fédérale (Belgique) = Belgian Federal Science Policy
Researchers ; Professionals ; Students
http://hdl.handle.net/2268/3997

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