Electron impact excitation of Fe XVIII from its ground state

The R-matrix method is used to calculate electron impact collision strengths for transitions in fluorine-like Fe XVIII from its ground 2 P O state. All states of the form 2p 5 , 2s2p 6 , 2p 4 3l are included as target states and are represented by configuration interaction wavefunctions constructed in LS coupling. Effective collision strengths are calculated for transitions between the fine-structure levels of the ground state and those of the excited states by employing a transformation of the LS-coupled reactance matrices using term coupling coefficients, and by assuming a Maxwellian velocity distribution for the incident electrons.