K-shell energy levels and radiative rates for transitions in Si ix

Abstract

Context. Accurate atomic data are needed to analyze the Si ix K-shell features in astrophysical X-ray spectra. Relative large discrepancies in the existing atomic data have impeded this progress. Aims. We present the accurate Si ix K-shell transition data, including K-shell energy levels, wavelengths, radiative rates, and oscillator strengths. Methods. The flexible atomic code (FAC), which is a fully relativistic atomic code with configuration interaction (CI) included, was employed to calculate these data. To investigate the CI effects, calculations with different configurations included were carried out. Results. The K-shell atomic data of Si ix transitions between 1s 22s22p2, 1s22s2p3, 1s22p4, 1s2s22p3, 1s2s2p 4, and 1s2p5 are reported. The accuracy of our data is demonstrated by comparing them with the available experimental measurements and theoretical calculations. The energy levels are accurate to 3.5 eV, the wavelengths to within 15 mÅ. For most transitions, the radiative rates an accuracy of 20%. The effects of CI from high-energy configurations were investigated as well. © 2014 ESO.