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Studies on carbon/sulfur cluster anions produced by laser vaporization: Experiment (collision-induced dissociation) and theory (ab initio calculation). I.C 2 S m − (1m11)An ab initio Hartree-Fock molecular dynamics procedure is applied to study structural and dynamical properties of Li 9 ϩ , Li 10 , and Li 11 ϩ clusters with eight and ten valence electrons, corresponding to ''closed'' and ''open'' shell systems. Gradients of the ground state energy are used to compute the forces acting on atoms at each geometric configuration along trajectories generated by solving classical equations of motion. Dynamics of different isomers for each cluster size have been investigated as a function of excess energy. It is shown that different isomers, even those similar in energy, can exhibit different structural and dynamical behavior. The analysis of the simulations leads to the conclusion that structures with a central atom, in particular the centered antiprism of Li 9 ϩ , exhibit concerted mobility of the peripheral atoms at relatively low excess energy. In contrast, compact tetrahedral type structures show much more rigid behavior at low excess energy. However, the former ones need larger excess of internal energy to undergo isomerizations to geometrically different structures than the latter ones, at least in the case of Li 9 ϩ and Li 11 ϩ clusters. At the time scale of our simulations we found that for the intermediate excess energies it is ''easier'' to carry the cluster in the basin of the lowest energy isomer than in the reverse direction. Moreover, for different cluster sizes isomerization processes occur at different excess energies ͑temperatures͒, which is a consequence of the differences in the structural properties rather than in the number of the valence electrons. It has been found that the liquidlike behavior in small Li clusters becomes apparent at relatively high temperature in spite of large mobility of their atoms.

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We find that the ab initio direct configuration-interaction calculations on Na−2–5 and Na2–5 account for the observed patterns of photoelectron spectra, reproduce the observed excitation energies in a semiquantitative way and permit an assignment of cluster geometries.

Abstract. The ground state geometries of small neutral Agn(n = 2-9) and charged Ag~ (n = 2-9) clusters have been determined in the framework of the SCF procedure employing a relativistic pseudopotential accounting for core-vMence correlation effects (RECP-CVC). Similarities and differences between neutral and charged clusters have been found. Large scale CI for 5s electrons only has been carried out for determining stabilities, ionization potentials (IP) and vertical detachment energies (VDE) of anions. A comparison between predicted and measured observables allows for the tentative structural assignments. In addition, the low lying energies of excited states for the neutral species at the anionic geometries have been calculated to account fully for geometrical and spectroscopic assignment to the photodetachment measurements.