INTEGRAL AND DIFFERENTIAL CROSS-SECTIONS FOR THE ELECTRON-IMPACT EXCITATION OF AR7+ IONS

Electron-impact excitation of Ar7+ is studied theoretically with the R -matrix method. Excitation cross sections are calculated for the trans itions from the ground state (3s) to the 3p, 3d, 4s, 4p and 4d excited states at the impact electron energies from threshold to 110 eV, allo wing for coupling between the lowest eleven states. All the cross sect ions show complicated resonance structure. Differential cross sections (DCSs) are also calculated for the 3s --> 3p, 3d, 4s transitions both at the resonance and at the off-resonance energies. The DCS at the of f-resonance position shows dominance of backward scattering. This is e xamined in more detail with the calculation of forward-backward asymme try parameter. At the resonance, DCS changes its shape. This is shown at several selected resonant peaks. The present theoretical cross sect ions well reproduce experimental data available for the 3s --> 3p tran sition.