Oscillator strengths of the resonance 4s-4p lines in ZnII

We have undertaken extensive configuration interaction calculations of the 4s S-2(1/2)-4p P-2(1/2,3/2)o lines of Zn II. Core polarization, which is confirmed as a significant effect in the determination of the oscillator strengths, is introduced through explicit configuration interaction rather than by means of model potentials. It is shown that the ab initio calculation of this effect gives results that are close to those obtained with model potentials which incorporate the polarizability of the Zn III core. The oscillator strengths are reduced to around 75 per cent of the single configuration value. We also find that the inclusion of electron correlation in the core causes the oscillator strength to rise again, although only marginally. Our final oscillator strengths, which incorporate all these effects, are 0.268 and 0.547 for the 4s S-2(1/2)-4p P-2(1/2)o and 4s S-2(1/2)-4p P-2(3/2)o lines, respectively. These values are in good agreement with recent many-body perturbation theory calculations of Johnson and with unpublished multiconfigurational Hartree-Fock or Multiconfigurational Dirac-Hartree-Fock (MCDHF) calculations of Froese Fischer, but lie about 5-10 per cent higher than the most recent experimental values obtained by Bergeson and Lawler.