Abstract
Absolute cross section measurements at energies from below threshold to 1500 eV are reported for electron impact ionisation of nickel ions with initial charges 5+, 6+, 7+, 8+, 12+ and 14+. The experimental data are compared with distorted-wave calculations for direct ionisation, which account for 40-80% of the measured peak total ionisation cross sections. The discrepancy is attributed to contributions to single ionisation due to excitation of inner-subshell electrons followed by autoionisation. Ionisation rate coefficients and fitting parameters based on the data are presented for charge states 5+ through 8+.
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