Resonance structure in elastic electron scattering from helium, neon and argon

High energy-resolution spectra of electrons scattered elastically from helium, neon and argon atoms have been obtained as functions of scattering angle and of incident electron energy. In addition to the well known levels of the lowest configurations of the temporary negative ions (resonances), the authors observe structures at energies close to those of the (core)np 5 (n+1)s levels of neon and argon. These structures are attributed to resonances having configurations (core)np 5 ((n+1)s(n+1)p 3 P). By calibration against features occurring at known energies in the elastic scattering spectra and also metastable excitation spectra they determine accurately the energies of the observed resonances.