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Quantum stereodynamics of Li + HF reactive collisions: the role of reactants polarization on the differential cross section.
González-Sánchez, L; Vasyutinskii, O; Zanchet, A; Sanz-Sanz, C; Roncero, O.
Afiliación
  • González-Sánchez L; Departamento de Química Física, Facultad de Ciencias Químicas, Universidad de Salamanca, 37008 Salamanca, Spain.
Phys Chem Chem Phys ; 13(30): 13656-69, 2011 Aug 14.
Article en En | MEDLINE | ID: mdl-21725558
A complete quantum study for the state-to-state Li + HF(v,j,m) → LiF(v',j',Ω') + H reactive collisions has been performed using a wave packet method, for different initial rotational states and helicity states of the reactants. The state-to-state differential cross section has been simulated, and the polarization of products extracted. It is found that the reactivity is enhanced for nearly collinear collisions, which produces a vibrational excitation of HF, needed to overcome the late barrier. It is also found that LiF(v' = 0) products are preferentially forward scattered, while vibrationally excited LiF(v' = 1 and 2) are backward scattered. These results are interpreted with a simple reaction mechanism, based on the late character and bent geometry of the transition state, originating from a covalent/ionic crossing, which consists of two steps: the arrival at the transition state and the dissociation. In the first step, in order to get to the saddle point some HF vibrational excitation is required, which favors head-on collisions and therefore low values of m. In the second step a fast dissociation of H atom takes place, which is explained by the ionic Li(+)F(-)H character of the bent transition state: the FH(-) is repulsive making that H depart rapidly leaving a highly rotating LiF molecule. For the higher energy analyzed, where resonances slightly contribute, the orientation and alignment of product rotational states, referred to as reactants frame (with the z-axis parallel to k), are approximately constant with the scattering angle. The alignment is close to -1, showing that j' is perpendicular to k, while starting from initial states with well defined rotational orientation, as states with pure m values, the final rotational are also oriented. It is also found that when using products frame (with the z'-axis parallel to k') the rotational alignment and orientation of products varies a lot with the scattering angle just because the z' axis changes from being parallel to anti-parallel to k when varying from θ = 0 to π.

Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Phys Chem Chem Phys Asunto de la revista: BIOFISICA / QUIMICA Año: 2011 Tipo del documento: Article País de afiliación: España Pais de publicación: Reino Unido

Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Phys Chem Chem Phys Asunto de la revista: BIOFISICA / QUIMICA Año: 2011 Tipo del documento: Article País de afiliación: España Pais de publicación: Reino Unido