Electron impact excitation of AI XIII: Collision strengths and rate coefficients

Collision strengths for transitions among the n = 5 levels of Al XIII have been computed in the LS coupling scheme using the R-matrix code. All partia l waves with angular momentum L less than or equal to 45 have been included , and resonances have been resolved in a fine energy grid in the threshold region. Collision strengths have been computed at energies below 220.0 Ryd, and effective collision strengths, obtained after integrating the collisio n strengths over a Maxwellian distribution of electron velocities, are calc ulated over a wide temperature range of 4.40 less than or equal to log T-e less than or equal to 6.0 K.