[en] Single crystals of CH₃COOLi . 2H₂O irradiated at 77 degreeK gave ESR signals arising from triplet radical pairs in addition to CH₃ radicals. Spectral analyses lead to the conclusion that a pair of CO₂^- ions are formed with the average separation of 5.95 A. The unpaired electrons extend over the four neighboring Li cations giving 13-line superhyperfine structures. Strong nuclear spin forbidden transitions arising from the anisotropic coupling with ⁷Li nuclei were observed in one of the fine structure components. From this behavior the sign of the isotropic coupling of ⁷Li was determined to be positive. The structure and the trapping site of the paired CO₂^- ions interacting with Li were elucidated from the g and D tensors as well as the ⁷Li and ¹³C hyperfine coupling tensors. The isolated CO₂^- ions in the crystals annealed at room temperature have been found to undergo hindered oscillation around the Ocenter-dotcenter-dotcenter-dotO axis at 77 degreeK. As a very minute component the radical pairs of CH₂CO₂^- were also found in the crystal stored at 77 degreeK after irradiation