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We performed accurate calculation of $\alpha$-dependence ($\alpha=e^2/hc$) ofthe transition frequencies for ions, which are used in a search for thevariation of the fine structure constant $\alpha$ in space-time. We useDirac-Hartree-Fock method as a zero approximation and then the many-bodyperturbation theory and configuration interaction methods to improve theresults. An important problem of level pseudocrossing (as functions of$\alpha$) is considered. Near the crossing point the derivative of frequenciesover $\alpha$ varies strongly (including change of the sign). This makes itvery sensitive to the position of the crossing point. We proposed asemiempirical solution of the problem which allows to obtain accurate results.Comment: 8 pages, revtex4 class, 2 eps figure

physical review. a, atomic, molecular, and optical physics/physical review, a, atomic, molecular, and optical physics

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>dependence of transition frequencies for ions Si II, Cr II, Fe II, Ni II, and Zn II

αdependence of transition frequencies for ions Si II, Cr II, Fe II, Ni II, and Zn II