Electron scattering in ozone and chlorine dioxide

Total cross-sections are reported for the scattering of electrons from ozone (O-3) and chlorine dioxide (OClO) for energies in the range of 9 meV to 10 eV. The measurements were made in transmission experiments using synchrotron radiation photoionization apparatus with an energy resolution in the incident electron beam of similar to 3.5 meV (FWHM). The absolute accuracy of the cross-sections is limited both by experimental difficulties with respect to strong rotationally inelastic forward scattering, due to the dipolar nature of the target molecules, and by the composition of the target gases, which may depart significantly from pure O-3 or OClO. Very marked structure peaking at 50-60 meV in the spectrum of OClO, and a weak feature at a similar energy in O-3, may represent dissociative attachment. With respect to rotationally inelastic scattering, for O-3, we find that the first Born pure dipole approximation is adequate down to energies of 50-60 meV but fails at lower energies, very markedly overestimating scattering cross-sections between 10 and 50 meV. In OClO, the Born approximation fails seriously, even at energies as high as 1-1.5 eV.