Laser ablation of transition metal targets with concurrent code position of CS2/Ne and CS2/Ar mixtures produces metal independent absorptions at 1206.8 and 1159.2 cm(-1) in neon and 1200.5 and 1160.4 cm(-1) in argon due to CS2+ and CS2-. Additional metal independent absorptions at 1385.2 cm(-1) in neon and 1379.7 cm(-1) in argon increase on annealing. Isotopic substitutions show that this vibration involves two equivalent CS2 subunits. Based on density functional theory calculations of structure and vibrational frequencies, the 1385.2 and 1379.7 cm(-1) bands are assigned to the C2S4+ cation in solid neon and argon. Identical experiments using matrix samples doped with the electron trapping molecule CCl4 enhance the 1385.2 and 1379.7 cm(-1) absorptions and further support the cation assignment. No evidence was found for the (CS2)(2)(-) anion in these experiments. (C) 2000 American Institute of Physics. [S0021-9606(00)00715-7].