Electron-impact excitation of Ne⁴⁺

We present the results of extensive close-coupling calculations of electron-impact excitation of the C-like ion, Ne 4+ . We first compare effective collision strengths determined from a 20-level Breit-Pauli R -matrix calculation with those obtained from a 20-level intermediate-coupling frame transformation (ICFT) R -matrix calculation. The ICFT method was also employed to perform two much larger calculations; we compare the effective collision strengths determined from these calculations with each other and with those obtained from the 20-level calculations in order to assess the effects of increasing both the size of the configuration-interaction expansion of the target and the size of the close-coupling expansion. Our final calculation, with 130 terms and 261 levels in the configuration-interaction expansion of the target and 66 terms and 138 levels in the close-coupling expansion, provides improved data for excitation between the levels of the 2s 2 2p 2 , 2s2p 3 and 2p 4 configurations and the first close-coupling results for excitation to the levels of the 2s 2 2p3ℓ configurations in Ne 4+ .