Effective Gaunt Factors geff for Excitation of Positive Ions by Electron Collisions in a Simplified Coulomb-Born Approximation

Effective Gaunt factors g~ have been calculated for threshold excitation of positive ions by electrons for transitions in fifteen isoelectronic sequences. A simplified Coulomb-Born approximation is used, the validity of which is given by the inequality (8). Results are presented as a function of Z/k, where ~`k2 is the excitation energy in atomic units