Measurement of ionization rates of Ti ix, Ne vi, Ne vii, and O vi

The effective ionization rates of Ti ix, Ne vi, Ne vii, and O vi have been measured with the use of the plasma spectroscopy method in a θ pinch discharge at an electron temperature (50-60 eV) much below their ionization threshold and at an electron density of ({} 2-3)×{}10¹⁶ cm^-3. A theoretical analysis of the effective ionization rates showed that excitation ionization is a major contributing process. Theoretical values are in reasonable agreement with experiment.