Translational energies from triatomic negative ions fragmentation

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Abstract
The dissociation of triatomic negative ions is studied with a classical trajectory method. The initial conditions are represented by the Wigner probability density function; the Hamilton equations of the motion are solved using the Bulirsch–Stoer algorithm and the final averaged values are obtained through a Monte Carlo sampling method. The use of different molecular models allows an evaluation of the assumptions made in the former simpler model. An analytical semi‐empirical potential energy surface is built to represent an attractive negative ion state. The kinetic energy distributions calculated using such surfaces exhibit a maximum close to zero, opposite to what has been obtained with LEPS repulsive surfaces. The kinetic energy distributions appear to be relatively insensitive to the value of the autodetachment rate and to the shape of the surface. The main feature of the VFM surfaces is to introduce a strong translation to vibration coupling. Furthermore, the partitioning of the excess energy of the dissociation between translational and internal energies of the recoiling fragments, which favors the internal energy, is found to be independent of the amount of energy to be partitioned.