Electron distribution and intracluster reaction in [Na_n(CS ₂)₂]^- negative ion clusters

We have studied excess electron distributions of binary cluster negative ions consisting of sodium atoms and carbon disulfied molecules, Na _n(CS₂)₂ ^- (n= 1 and 2) by using photoelectron spectroscopy and quantum chemical calculations based on the density functional theory (DFT). The photoelectron spectra indicate the existence of at least two isomers for both n=1 and 2 anions. From the DFT calculations, mainly two types of isomers are found to coexist in the Na(CS ₂)₂ ^-; one has a van der Waals (vdW) type CS₂ dimer core and another has a covalently bonded C ₂S₄ core, both of which were known for CS₂ molecular cluster anions. In the latter isomers, the C₂S₄ portion possesses almost two electrons, which is caused by the valence electron transfer from the Na atom. Also for n=2, we found the isomers of vdW and covalently bonded types. In the isomers with covalently bonded core, the C ₂S₄ portion has more than two electrons, an excess electron and double valence-electron transfer from both of the sodium atoms.