Infrared spectra of the C_2O_4~+ cation and C_2O_4~- anion isolated in solid neon

摘要

Laser ablation of transition metal targets with concurrent 4 K codeposition of CO_2/Ne mixtures produces metal independent infrared absorptions at 1658.2 and 1421.6 cm~(-1) due to CO_2~- and CO_2~+. 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 CO_2 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 C_2O_4~+ cation with C_(2h) symmetry, and the 1852.4, 1189.2, and 679.2 cm~(-1) bands are assigned to the C_2O_4~- anion with D_(2d) symmetry. Evidence is also obtained for (CO_2~-)(CO_2)_x (x = 1,2) anion complexes.