Caos em um sistema pósitron-molécula

Abstract

The classical trajectories for a positron interacting collinearly with a vibrating molecule, are calculated in a search for a chaotic scattering behavior. The positron-molecule interaction has been modelled via coupled Morse potentials, which reproduce ab initio energies computedwith the Finite Nuclear Mass Correction (FNMC) method. The classical trajectories were obtained from integration of the Hamilton equations using a 4th-order symplectic algorithm. A first interesting result refers to the emergence of a chaotic behavior of the scattering function which relates the initial phase of the molecule with its final positronenergy. As is commonly observed in chaotic scattering, this function contains both smooth regions and discontinuities, which are characteristics of a fractal set. Interestingly, the transient chaotic region includes a set of trajectories which corresponds to a temporary trapping of the projectile by the target. These resonances accompanied by trappings were observed experimentally and described using quantum scattering calculations.