4s4dD1−4p2D1interaction in the Zn I isoelectronic sequence

The importance of the interaction between $4s4d{}_{}{}^1{}_{}{}^{}D$ and $4p^2{}_{}{}^1{}_{}{}^{}D$ is studied in the Zn I isoelectronic sequence from Zn I to W XLV. Multiconfiguration Hartree-Fock calculations have been carried out for the two lowest ${}_{}{}^1{}_{}{}^{}D$ terms in this sequence and used to calculate $\mathrm{gf}$ values for the ${}_{}{}^1{}_{}{}^{}P-{}_{}{}^1{}_{}{}^{}D$ transitions. For the heavier elements relativistic effects are important and intermediate-coupling calculations of the $\mathrm{gf}$ values using multiconfiguration Dirac-Hartree-Fock transition energies have been carried out. Final $\mathrm{gf}$ values take into account relativistic effects in an approximate way, as well as core-polarization effects. The latter are found to be as important for the ${}_{}{}^1{}_{}{}^{}P-{}_{}{}^1{}_{}{}^{}D$ transitions as for the ${}_{}{}^1{}_{}{}^{}S-{}_{}{}^1{}_{}{}^{}P$ resonance transition even for high-ionization stages. The $\mathrm{gf}$ values for transitions from the lowest ${}_{}{}^1{}_{}{}^{}D$ terms were found to be small due to destructive interference. Little experimental data exist with which the present results can be compared. Furthermore, it is shown that much of the earlier experimental material concerning the ${}_{}{}^1{}_{}{}^{}D$ terms are in error. Comparison with a few very recent experimental investigations shows good agreement, however, and the present results point to the need for further experimental studies of this sequence, even towards the neutral end.