Electron collisional excitation cross sectiosn for Ca XIII

Ab initio calculations are carried out for electron-impact excitation of Ca XIII ion in the R-matrix formalism using extensive configuration-interaction wavefunctions for the target. Collision cross sections are being calculated for all the transitions among n=2 and n=3 levels in LS as well as intermediate coupling scheme. Relativistic effects are included through the use of the Breit-Pauli Hamiltonian. A sufficient number of continuum orbitals are introduced to get converged results in the energy range of interest. All partial waves of even and odd parity which contribute significantly to the total collision strength are included in the calculation. Our results will be compared with those obtained in the distorted wave approximation