Relativistic oscillator strengths forE1transitions in the argon isoelectronic sequence

The relativistic electric dipole oscillator strengths in length and velocity forms are calculated for a number of elements in the argon sequence. The transitions studied are $3p^6-3\mathrm{}{p}^5\mathrm{nd}$ $(n=3, 4)$ and $3p^6-3\mathrm{}{p}^{5}4s$. The ground state includes correlation due to the configuration $3p^{4}3d^2$ in computing $p-d$ transitions. Relativistic effects on line strengths are found to be important in the $\Delta n\ne 0$ transitions even at low $Z$. The origin of these large relativistic effects for low $Z$ in the $3p^6-3\mathrm{}{p}^{5}4l$ transitions are discussed.