Measurement of electron impact excitation cross sections for heliumlike titanium

We have obtained the first measurement of electron impact excitation cross sections as a function of energy for a highly charged ion. Collisional excitation cross sections to four n=2 levels of He-like titanium were measured from threshold to 1.7 times threshold. The data conform well to established theory, especially for direct excitation; however, significant differences are found with predicted contributions from resonance excitation and in the treatment of radiative cascades. The latter changes plasma temperatures inferred from titanium K{α} line intensities by as much as a factor of 2.