LOW-ENERGY ELECTRON-SCATTERING BY SF6

In a crossed-beam experiment we have studied elastic and vibrationally inelastic scattering of electrons by SF6 over the energy range 50 meV to 1 eV at a fixed angle of 90-degrees. A synchrotron photoionization source was used to form a primary beam of electrons of energy resolution FWHM of about 5 meV. Scattered electrons were analysed with an energy resolution of 11.5 meV allowing us to study the excitation of close lying vibrational modes independently. We present excitation functions for nu-1, nu-3, 2-nu-1 and nu-1 + nu-3. Excitation of nu-3 takes place through a direct dipole mechanism whereas we suggest that nu-1 involves a long-lived negative ion resonance.