Electron collisions with formic acid monomer and dimer.

Processes induced by the attachment of slow electrons to formic acid and its hydrogen-bonded dimer were studied. The elastic cross section and the cross section for the excitation of low quanta of discrete vibrations were found to be of a similar magnitude for both targets. A dramatic difference was found in the excitation of a vibrational quasicontinuum in the 1-2 eV range with the ejection of very slow electrons (E<0.1 eV), which was about 20x more intense in the dimer. The association of two formic acid molecules to form a dimer thus dramatically increases the power to quasithermalize electrons arriving with energies in the 1-2 eV energy range. Rapid electron-driven intracluster proton transfer is invoked to explain the observation.