Reference : Wave packets in a bifurcating region of an energy landscape: Diels-Alder dimerization of...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
Physical, chemical, mathematical & earth Sciences : Physics
Wave packets in a bifurcating region of an energy landscape: Diels-Alder dimerization of cyclopentadiene
Lasorne, Benjamin [> > > >]
Dive, Georges mailto [Université de Liège - ULg > > Centre d'ingénierie des protéines >]
Desouter, Michèle mailto [Université de Liège - ULg > Département de chimie (sciences) > Département de chimie (sciences) >]
Journal of Chemical Physics
Amer Inst Physics
184304 1-10
Yes (verified by ORBi)
[en] Quantum dynamics in a valley ridge inflection (VRI) point region is analyzed in the case of the Diels-Alder endo-dimerization of cyclopentadiene pointed out recently by [Caramella , J. Am. Chem. Soc. 124, 1130 (2002)]. The VRI point is located along the reaction path connecting the bispericyclic symmetrical transition structure put in evidence by Caramella and the transition state of the Cope rearrangement. Dynamics is carried out by using constrained Hamiltonian methodology. The active coordinates are the first formed C-C bond length and the difference between the two other C-C bond lengths which achieve the dimerization as 4+2 or 2+4 adducts. A two-dimensional (2D) minimum-energy surface have been computed at the Becke 3 Lee-Yong-Parr/6-31G(*) level. The energy landscape can be classified as an uphill ridge-pitchfork VRI bifurcation according to a recent classification of bifurcation events [W. Quapp, J. Mol. Struct. 695-696, 95 (2004)]. Dynamics does not describe the thermal reaction but concerns wave packets which could be prepared by pulse reagents, i.e., by coherent control. We analyze how the shape and initial location on the ground potential-energy surface are linked to the synchronous or asynchronous mechanism of the final step after the first transition state. We use a one-dimensional model of optimum control theory to check the feasibility of such a coherent preparation. The wave-packet evolution in the VRI domain is well explained by semiclassical predictions even with the negative curvature of the unstable ridge. Finally, a crude model of dissipation has been introduced to test the stability of the 2D predictions. (c) 2005 American Institute of Physics.
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