ELECTRON-IMPACT IONIZATION OF AR9+

We have calculated total and single differential cross sections for el ectron-impact ionization of Ar9+ in its ground (1s(2)2s(2)2p(5)) P-2(0 ) State by using a method that combines the distorted-wave Born approx imation and the R-matrix theory. The incident and the scattered electr ons are described by distorted waves, while the wavefunctions of the i nitial ground state of the Ar9+ ion and its final continuum state (Ar1 0+ + e(-)) are calculated by using the R-matrix approach. This allows us to take into account the excitation-autoionization process. Five st ates of the final Ar10+ ion, namely 1s(2)2s(2)2p(4) P-3, D-1, S-1 and 1s(2)2s(2)p(5) P-3(0), P-1(0) have been included in our calculation. U p to the 2(4)-pole components of the interaction with the ionizing ele ctron were included, exciting ten distinct Ar9+ continuum symmetries. The single differential cross sections exhibit considerable structure due to autoionizing resonances. Total cross sections for production of Ar10+ in each of the five states are presented for impact energies fr om the threshold energy at 17.6 to 100 au. Our theoretical values for the total cross section are in fair agreement with the experimental re sults.