THEORETICAL-STUDY OF THE VISIBLE PHOTODISSOCIATION SPECTRUM OF AR-3+

The photodissociation of Ar3+ is studied following a consistent theoretical approach from the Potential Energy Surfaces to the dynamics. Six P.E.S. are computed according to a D.I.M.-like model Hamiltonian. Transition dipole moments are determined using a similar method. The 4-D dynamics of this system is obtained with the H.W.D. method (Hemiquantal dynamic with the Whole DIM basis). All the 4 nuclear degrees of freedom and all the 6 electronic states are involved in the dynamical calculations, allowing for very general investigations. The main theoretical results are: - the spectrum essentially results from a SIGMA-u --> SIGMA-g transition to the second excited electronic state along with a symmetric stretching motion, - excited Ar3+ molecules almost all dissociate in Ar+ + 2 Ar, - dissociation in Ar2+ + Ar requires special conditions such as low laser excitation and is predicted to increase with a specific excitation of the bending mode, - the dominant symmetric stretching motion induces a bimodal kinetic energy distribution of the fragments. All these points are in close agreement with experimental results.