Resonances in collisions of low-energy electrons with ozone: Experimental elastic and vibrationally inelastic differential cross sections and dissociative attachment spectra

Abstract

A comprehensive study of the elastic and vibrationally inelastic scattering of low-energy electrons on ozone, as well as of the dissociative electron attachment has been carried out. Absolute differential cross sections (DCSs) for the elastic and vibrationally inelastic scattering are presented as a function of electron energy and of scattering angle. The elastic data are compared to existing experimental and theoretical work. Two shape resonances are observed in the vibrational DCSs, peaking at 4.2 and 6.6 eV. We used the Koopmans theorem to assign them as and , with temporary capture of the incident electron into orbitals which are very strongly antibonding with respect to the O - O bond length. Both resonances excite not only the totally symmetric vibrations and , but also the antisymmetric stretch vibration , and we assign the excitation of the latter to vibronic coupling between the resonances. Dissociative electron attachment below 5 eV yields and with considerable intensity. formation through three-body attachment or ion - molecule reactions is also observed. Four resonant peaks are observed in the dissociative attachment spectra, at 0.4 eV, 1.3 eV, 3.2 eV, and 7.5 eV. The ions are formed with moderate kinetic energies for the first, nearly zero kinetic energy for the second, and large kinetic energies for the third resonance. The resonances in the dissociative attachment spectra are assigned as the `high energy tail' of the ground state of , a core excited resonance, the shape resonance, and a Feshbach resonance, respectively. The shape resonance appears at a lower energy in the dissociative attachment channel than in the vibrational excitation channel because of kinetic shift. Angular distribution and approximate absolute values are given for the formation at 3.2 eV.