Photodestruction spectra of carbon disulfide cluster anions, (CS2)n−, n=1–4, have been measured with a time-of-flight mass spectrometer coupled with an optical parametric oscillator. The spectra of all the cluster anions of n⩾2 were found to exhibit a similar absorption band peaking at 1.6–1.8 eV, suggesting that a C2S4− core is involved in the cluster anions. Photon energy dependence of competition between electron detachment and dissociation of the dimer anion was also observed. It was found that there is a reaction channel of the dimer anion producing C2S2− and S2, as well as the ordinary dissociation into CS2− and CS2. The most stable form of the dimer anion was investigated by ab initio calculations at the unrestricted Hartree–Fock/6-31+G* level, showing that the stable form involves covalent C–C and S–S bonds. Reaction mechanisms are discussed on the basis of electronic symmetries of the parent and the fragments.

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