Rings and chains in sulfur cluster anions S− to S9−: Theory (simulated annealing) and experiment (photoelectron detachment)

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Abstract
Density functional calculations with simulated annealing have been performed for singly charged anions of sulfur clusters with up to nine atoms. The calculations predict the existence of two classes of structure: open (chain‐like) and closed (ring‐like), for which the vertical detachment energies (VDE) and the adiabatic electron affinities for transitions to states of the neutral clusters show pronounced differences. These calculations are complemented by photoelectron detachment measurements on sulfur cluster ions with up to 11 atoms using a pulsed arc cluster ion source (PACIS). The measurements provide unambiguous evidence for the existence of two types of isomers in both S6− and S7−. Although ring structures are generally energetically more stable than chain structures, the environment used to generate the larger clusters (n≳7) favors the formation of the latter. The measured VDE and vibration frequencies agree well with the calculated values.