Carbon Dioxide as an Electron Trap in 3-Methylpentane at 77°K

The narrow paramagnetic resonance in a photolyzed 3-methylpentane system at 77°K, previously assigned tentatively to the ``solvated'' electron, is characterized and assigned to the carbon dioxide radical anion. The ionization potential of CO2− is bracketed between 2.3 and 2.9 eV. A hyperfine splitting of 122 G is obtained for the species 13CO2−, and a value of −0.32 is calculated for the coefficient of the 2s atomic orbital in the 4a1 (C2v) molecular orbital of CO2−.