Excitation of Ne VIII by electron impact

Collision strengths for electron impact excitation of Ne VIII are calculated at 14, 18, and 30 Ry in a 5-state close coupling expansion and the unitarized Coulomb–Born approximation. To assess the importance of exchange and coupling beyond the 5 states, additional calculations are made at 18 Ry in 5-state and 8-state close coupling expansions without exchange. For the 2s–2p excitation, calculations below the 3s threshold at 10.0 Ry are made in a 2-state close coupling expansion at 1.6, 3.2, and 8.0 Ry. In most instances the close coupling method gives results which differ by 15% or less from those of the unitarized Coulomb–Born approximation and by 20–70% from the CBI (Coulomb–Born) results of Bely. Rate coefficients which are calculated from the results obtained in the close coupling approximation agree within experimental error with the experimental results of Kunze and Johnston and Haddad and McWhirter with the exception of the rate coefficient for the 2p → 3d excitation.