A generalized darc RMPS approach for the electron-impact ionization and excitation of C i from ground and excited states

The modeling and spectral interpretation of carbon impurities in laboratory fusion plasmas requires accurate electron-impact ionization and excitation data. The rate of ionization is often dominated by ionization from excited states, with low charge states of carbon also requiring non-perturbative quantum mechanical calculations. For such data to be useful, it needs to be coupled with accurate electron-impact excitation data. Thus, we have calculated new electron-impact ionization and excitation data for neutral carbon (C i). We generalize the approach taken for hydrogen by Badnell [N. R. Badnell 2008 J. Phys. B: At. Mol. Opt. Phys. 41 175202 (2008)], and expand upon the use of the Dirac Atomic R -matrix Codes (darc) in a similar way to the R -matrix with Pseudostates (RMPS) approach for the ionization of multi-electron systems. This allows both ionization and excitation rates to be calculated from the same initial target structure. Furthermore, the darc R -matrix with Pseudostates (DRMPS) method allows non-perturbative level-resolved excited state ionization cross sections to be calculated for the lowest lying 42 levels of C i. There is good agreement in both the ionization and excitation data with available measurements and other theoretical calculations. This provides confidence in a generalized DRMPS approach when considering non-hydrogenic systems. The availability of both electron-impact excitation and ionization rates allows for the determination of effective ionization rates through collisional radiative calculations. We show that for magnetically confined plasmas, the ionization contributions from excited levels have a non-trivial effect on the effective ionization rate coefficients of C i.