Dissociation Dynamics of Anionic Carbon Dioxide in the Shape Resonant State ²Π_u

Dissociative electron attachments via the lowest shape resonant state ²Π_u of CO₂^-, e^- + CO₂ → O^- + CO, are investigated with our high-resolution anion velocity map imaging apparatus. The production efficiency curve of O^- obtained in this work is consistent with those reported previously. The forward-backward asymmetric distribution superimposed on the isotopic background is observed in the time-sliced velocity image of O^- yield, implying that the dissociation of CO₂^-(²Π_u) proceeds through a combinational motion of bond stretching and bending. Thereby, the coproduct CO is proposed to be in the rovibrational states. The long-standing arguments about the dissociation dynamics of CO₂^-(²Π_u) are settled.