Electron collisional excitation of semi-forbidden transitions from the n=1 and n=2 states to the n=3 states in Mg XI

The total collision strengths for the 26 semi-forbidden transitions from the n=1 and 2 states to the n=3 states in Mg XI have been calculated using the R-matrix method. Sophisticated configuration interaction wavefunctions are used to represent the eleven target states which are included in the calculation. Results are presented for the effective collision strengths for the temperature range 4*10 4 -4*10 7 K.