Lawrence Berkeley National Laboratory

Dissociative electron attachment to N-ethylacetamide is investigated using velocity map imaging with a tunable electron beam. Previously reported ion-yield spectra reveal two prominent resonant features near 5.5 and 8.8 eV across all observed anion channels. Surprisingly, no distinct structure is observed in the intermediate 6–7-eV energy region, where smaller amides typically exhibit an additional resonance associated with amide-bond cleavage. For N-ethylacetamide, the absence of a clear feature in this energy region indicates that any corresponding transient negative-ion state does not contribute significantly to dissociation. The momentum distributions obtained in the present work reveal distinct dissociation dynamics for different channels. The CH3− fragment at 5.5 eV exhibits an anisotropic distribution, indicating a direct dissociation process with finite kinetic-energy release. In contrast, the NH− fragment at 8.8 eV shows an isotropic distribution with near-zero kinetic energy, which suggests a three-body dissociation process. These results demonstrate that the observed resonances correspond to qualitatively different dissociation mechanisms and suggest that the intermediate resonance, if present, does not drive efficient or direct fragmentation in N-ethylacetamide.