Electron-impact ionization and excitation of Si⁺ for applications in laboratory and astrophysical plasmas

Accurate electron-impact data for Si ions is essential for determining Si abundances in astrophysics and erosion characteristics for laboratory plasma facing components. A new calculation of electron-impact data for Si⁺ using the R-matrix with pseudo-states (RMPS) method has been carried out. Both ground state and excited state ionization cross sections have been calculated. The ground state ionization cross section shows excellent agreement with crossed beams experimental measurements; however, the authors are aware of no other data with which to compare the excited state ionization cross sections. Excited state ionization cross sections are significant because they have proven essential in existing plasma diagnostics for other species (e.g. Li, Be, B, W). Excitation calculations have also been performed, which are used to generate atomic coefficients representing “ionizations per photon” (S/XB) which are needed for erosion diagnostics of plasma facing components. Generalized atomic coefficients for Si⁺ have particular relevance for Si as a plasma facing component of fusion relevant experiments.