Ion-momentum imaging of resonant dissociative-electron-attachment dynamics in methanol

A combined experimental and theoretical investigation of the dissociative-electron-attachment (DEA) dynamics in methanol are presented for the Feshbach resonance at 6.5-eV incident electron energy. Highly differential laboratory-frame momentum distributions have been measured for each fragmentation channel using a DEA reaction microscope. These measurements are combined with calculations of the molecular-frame electron attachment probability in order to investigate the dynamics of the dissociating methanol transient negative anion. In contrast to previous comparisons between water and methanol [Curtis and Walker, J. Chem. Soc., Faraday Trans. 88, 2805 (1992); Prabhudesai, Nandi, Kelkar, and Krishnakumar, J. Chem. Phys. 128, 154309 (2008)], we find subtle differences in the dissociation dynamics of the two fragment channels that are direct evidence of planar symmetry-breaking of warm methanol in its electronic ground state. We also find that the DEA fragmentation does not strictly follow the axial recoil approximation and we describe the dynamics that enable an accurate prediction of the fragment angular distributions.