A new theoretical approach is presented for the general treatment of nonadiabatic hybrid dynamics (mixing classical and quantum approach) and applied to the postionization of rare-gas trimers. There was an important disagreement between trajectory surface hopping (TSH) or mean field (MF) approaches and the experimental results; noteworthy, with the new method qualitative and almost quantitative agreement is found for the fragmentation ratios of ionic monomers and dimers. For the first time in the theory as in the experiment, the dimers prevail for argon while monomers strongly dominate for the heavier rare gases, krypton and xenon. A new compromise between MF and TSH approaches is proposed and the new method is found quite robust with results not too sensitive to various possible implementations.
The dynamics of ionic rare-gas trimers (Ar(3) (+), Kr(3) (+), and Xe(3) (+)) produced by a sudden ionization of neutral precursors is investigated theoretically with a hybrid classical-quantum method for solving the equations of motion governed by a Hamiltonian obtained from a previously tested diatomics-in-molecules model. Initial conditions are selected with Monte Carlo sampling. Two possibilities for generating the initial electronic state are considered: diabatic (local) and adiabatic (delocalized). The dynamics generally leads to fragmentation, producing either monomer ions or dimer ions in a relatively short time; however, a large number of long-lived metastable trimer ions are also seen in some cases. We have analyzed the dynamics with respect to the fraction of monomer ions produced, the distribution of the kinetic energy of the products, and the distribution of fragmentation times of the trimers. Initial diabatic ionization is associated with much faster fragmentation than adiabatic ionization. Spin-orbit coupling plays an important role in the fragmentation dynamics.
A dynamical model combining an extended diatomics-in-molecules approach with the inclusion of the spin-orbit coupling and the mean-field dynamics method has been developed for rare-gas cluster cations, Rg + n , and employed in simulations of the photodissociation dynamics of argon, krypton, and xenon singly charged trimers. As the first step, total kinetic energies deposited in the photofragments are calculated for all the three rare gases and for a wide range of photon energies, and compared with available experimental data. A very good agreement between experiment and theory is reached, including a plausible theoretical explanation for an abrupt change in the total kinetic energy of photofragments at about 2.5 eV of photon energy, which was recently observed experimentally for Xe + 3 (and also, but less clearly for Ar + 3 ).
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