Laser ablation of transition metal targets with concurrent 4 K codeposition of CO2/Ne mixtures produces metal independent infrared absorptions at 1658.2 and 1421.6 cm(-1) due to CO2-and CO2+. Additional metal independent absorptions at 2130.8 and 1274.4 cm(-1), and at 1852.4, 1189.2, and 679.2 cm(-1) increase on annealing to 8 K. Isotopic substitution shows that both band sets involve two equivalent CO2 subunits. Based on density functional theory calculations of structures and vibrational frequencies, the 2130.8 and 1274.4 cm(-1) bands are assigned to the C2O4+ cation with C-2h symmetry, and the 1852.4, 1189.2, and 679.2 cm(-1) bands are assigned to the C2O4+ anion with D-2d symmetry. Evidence is also obtained for (CO2-)(CO2)(x)(x = 1,2) anion complexes.