Dirac B-spline R-Matrix Calculations for e--Xe$^+$ collisions.

Xenon is the most important ingredient for electric propulsion systems, including Hall and ion thrusters. The performance of these devices depends critically on the kinetic processes involving Xe$^+$ ions. However, in numerical simulations of such thrusters, excited states of Xe$^+$ cannot be studied due to the lack of fundamental cross-section data. Also, ionic emission lines are absent in the non-invasive diagnostic approach of optical emission spectroscopy, due to the lack of collisional-radiative models based on a reliable set of atomic data. We applied a relativistic Dirac B-spline R-matrix (DBSR) method to calculate oscillator strengths and electron-impact excitation cross sections for the $\rm 5s^25p^5,~5s5p^6,~5p^46s,~5p^45d,~5p^46p,~5p^47s$, and $\rm 5p^46d$ states of Xe$^+$, which exhibits a complex open-shell structure with strongly term-dependent orbitals. The excitation cross sections from the ground, metastable, and quasi-metastable states of Xe$^+$ are analyzed. We will use the present e--Xe$^+$ cross sections together with those obtained for e--Xe~[1] to build a complete CR model and to compare its predictions with experimental data from Hall and ion thrusters. [1] O.~Zatsarinny and K.~Bartschat, Phys. Scr. T{\bf 134} (2009) 014020.