Dissociative electron attachment to acetaldehyde, CH₃CHO. A laboratory study using the velocity map imaging technique

A detailed experimental investigation of the dissociative electron attachment (DEA) process to acetaldehyde, CH3CHO is presented. To investigate this process we use a time of flight spectrometer coupled with the velocity slice imaging technique. DEA in CH3CHO is found to lead to the formation of CH3−, O−, OH−, C2H−, C2HO− and CH3CO− anionic products produced through scattering resonances in the electron energy range of 6 to 13 eV. Of these product ions only O− is formed with any measurable kinetic energy distribution indicating a two-body dissociation process. CH3CO−, although formed with very low kinetic energy, shows anisotropy in the velocity slice image, indicating ejection of the H atom in the 180° direction with respect to the electron beam. The low kinetic energy distributions and absence of any anisotropy in the angular distributions of the other product ions indicate that they are formed through multiple fragmentation of the transient molecular negative ion. The angular distribution of O− is analysed in terms of the various partial waves