  We present an accurate ab initio method of calculating transition energies
and isotope shifts in the 3d-transition metals. It extends previous work that
combines the configuration-interaction calculation with many-body perturbation
theory by including the effective three-body interaction and modification of
the energy denominator. We show that these effects are of importance in Ti II.
The need to develop methods that can accurately calculate isotope shifts in
3d-transition metals comes from studies of quasar absorption spectra that seek
to measure possible variation of the fine-structure constant alpha over the
lifetime of the Universe. Isotope shift can also be used to measure isotope
abundances in gas clouds in the early Universe, which are needed in order to
test models of chemical evolution.
