  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.
