ELASTIC AND INELASTIC-SCATTERING OF HE+ BY HE IN THE ENERGETIC AND ANGULAR RANGES 5 TO 40 KEV AND 0.5 TO 3-DEGREES

The authors have measured the differential cross section for the elastic scattering, target and projectile excitation (corresponding to energy losses of about 21 eV and 40 eV) and for the double-excitation process (Q approximately=60 eV). Over the whole energy range, the elastic cross section shows oscillations of which extrema are located at particular values of tau ( tau =E0 theta ). These oscillations are due to the interference between the waves scattered through the Sigma u and Sigma g states and they have particularly studied the phaseshift between these waves, starting from Everhart's calculations. Moreover, the minima of the elastic process appear for some energies and do not exist for others as is expected from Everhart's results. For inelastic processes, the general behaviour is roughly the same.