ELECTRON-IMPACT FINE-STRUCTURE TRANSITIONS IN CU-XX FROM ITS GROUND-STATE

The R-matrix method is used to calculate collision strengths for elect ron-impact excitation of Cu XX from its ground state. Configuration in teraction wavefunctions are used to represent the lowest 15 LS coupled states which are retained in the R-matrix expansion. Effective collis ion strengths are calculated for transitions from the ground state to fine-structure levels of the excited states by employing a transformat ion of the LS coupled reactance matrices, and by assuming a Maxwellian distribution for the incident electron. This is the first detailed ca lculation on this ion in which the effects of exchange, channel coupli ngs and short-range correlation effects are taken into account.