ATOMIC DATA FROM THE IRON PROJECT .9. ELECTRON-EXCITATION OF THE P-2(3 2)O-P-2(1/2)O FINE-STRUCTURE TRANSITION IN CHLORINE-LIKE IONS, ARII TO NIXII/

Calculated effective collision strengths for the ground term fine-stru cture transitions of 11 chlorine-like ions (17 electrons) from Ar II t o Ni XII are presented. There is currently very little published data for this sequence and so there is a strong motivation to satisfy the n eed for this information and to improve upon the accuracy of previous work where it does exist. The data are calculated using R-matrix techn iques and are provided over a temperature range from 10(3) K up to 10( 7) K over which the target models should be valid. Accuracy for the ef fective collision strengths is in the region of 10%. An independent ca lculation on Fex recently published by Mohan et al. (ApJ 434, 389) is shown to be wrong for this transition because of their omission of imp ortant low-energy contributions.