Electron Collisions with Formic Acid

Low-energy electrons ($<$2 eV) can vibrationally excite as well as fragment gas phase formic acid (HCOOH) molecules through resonant collision processes. Recent experiments have shown that the principal reaction products of dissociative electron attachment are formate ions (HCOO$^-$) and hydrogen atoms. Using first-principles electron scattering calculations, we have identified the responsible negative ion state as a transient $\pi^*$ anion. Symmetry considerations dictate that the associated dissociation dynamics are intrinsically polyatomic: the anion must first deform to non-planer geometries before dissociating on a second anion surface that can be reached through a conical intersection. The calculations we have performed that support these conclusions will be described. We will also present differential and integrated elastic scattering cross sections and compare our results with recent experiment.