Electron impact collision strengths in Si IX, Si X and Si XI
  Electron impact collision strengths among 560 levels of Si IX, 320 levels of Si X and 350 levels of Si XI have been calculated using the Flexible Atomic Code (FAC) of Gu (2003). Collision strengths $\Omega$ at ten scattered electron energies covering an entire energy range, namely 10, 50, 100, 200, 400, 600, 800, 1000, 1500 and 2000 eV, are reported. Assuming a Maxwellian energy distribution, effective collision strengths $\Upsilon$ are obtained at a finer electron temperature grids of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 MK, which covers the typical temperature range of astrophysical hot plasma. Additionally, radiative rates $A$ and weighted oscillator strengths $gf$ are given for more possible transitions among these levels. Comparisons of our results with available predictions reported in earlier literatures are made, and the accuracy of the data is assessed. Most transitions exhibit a better agreement, whereas large differences in $gf$ appear for a few cases, which are due to the different inclusion of configuration interaction in different theoretical calculations. In excitations among levels of ground and lower excited configurations, large discrepancies of $\Upsilon$ maybe resulted from the consideration of resonance effects in earlier works. 
Guiyun Liang, Gang Zhao, and Jiaolong Zeng