Ab initio Calculations on the Structures of HC_nS⁺ and HSC_n⁺ （n=1～9）

Carbon cluster ions with a sulfur atom and a hydrogen atom have been generated in the experiments. The recorded mass spectra show that the cluster ions with odd number of clustering carbon atoms are more stable. To verify the experimental observations, ab initio calculations on HF/6-31G^* level were carried on the species. Two structural isomers, HC_nS⁺ and HSC_n⁺, have been considered in the calculation, and the former is found to be more stable. Based on the optimized geometry, the total system energy, the energy difference between the neighboring cluster ions, the average binding energy per clustering carbon atom and the fragmentation energies of six dissociation channels have been calculated. All calculated results exhibit the odd/even alternation and indicate that the cluster ions with odd n are more stable, which agrees very well with the experimental results.