ELECTRON-ATTACHMENT TO OXYGEN AND OXYGEN OZONE CLUSTERS STUDIED IN A HIGH-RESOLUTION CROSSED BEAMS EXPERIMENT/

Highly monochromatized electrons (with 30 meV FWHM) are used in a cros sed beams experiment to investigate electron attachment to oxygen clus ters (O-2)(n) at electron energies from approximately zero eV up to 2 eV. At energies close to zero the attachment cross section for the rea ction (O-2)(n) + e --> O-2(-) varies inversely with the electron energ y, indicative of s-wave electron capture to (O-2)(n). Peaks in the att achment cross section present at higher energies can be ascribed to vi brational levels of the oxygen anion. The vibrational spacings observe d can be quantitatively accounted for. In addition electron attachment to mixed oxygen/ozone clusters has been studied in the energy range u p to 4 eV. Despite the initially large excess of oxygen molecules in t he neutral clusters the dominant attachment products are undissociated cluster ions (O-3)(m)(-) including the O-3(-) monomer while oxygen cl uster ions (O-2)(n)(-) appear with comparatively low intensity.