ATOMIC DATA FROM THE IRON PROJECT .11. THE P-2(1 2)DEGREES-P-2(3/2)DEGREES FINE-STRUCTURE LINES OF AR-VI, K-VII AND CA-VIII/

We give collision strengths and collision rates for electron excitatio n of the P-2 degrees(1/2) - P-2 degrees(3/2) fine-structure transition s in the aluminium-like ions Ar VI, K VII and Ca VIII, a; 4.53, 3.19 a nd 2.32 mu respectively. The ground configuration of ions in the alumi nium sequence has three electrons in the M-shell. Electron correlation effects are very strong in these ions because the subshells are energ etically very close. They manifest themselves in large resonance struc tures that dominate the collision strengths. The accuracy of calculate d collision rates depends critically on the accuracy with which the po sitions and shapes of these resonances are determined. This paper is a first attempt to provide collision rates for aluminium sequence ions that have been calculated taking full account of these electron correl ation effects.