Calculated energy levels, oscillator strengths and lifetimes in Al-like argon

Excitation energies. oscillator strengths and transition probabilities for electric-dipole-allowed and inter-combination transitions among the 25 LS levels belonging to the (1s(2)2s(2)2p(6))3s(2)3p. 3s3p(2), 3s(2)3d, 3p(3), 3s3p3d, 3s(2)4s, 3s(2)4p, 3s(2)4d, 3s(2)4f and 3s3p4s configurat ions of Ar VI are calculated using extensive configuration-interaction (CI) wave functions. From our transition probabilities we have also calculated the radiative lifetimes of doublet and quartet states of Ar VI. Our results are compared with other available theoretical calculations and the experimental data. To assess the importance of relativistic effects on our calculated values, we have also carried out calculations in the intermediate-coupling scheme. These effects are incorporated through the Breit-Pauli approximation via spin-orbit. spin-other-orbit, spin-spin, Darwin and mass correction terms. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the experimental values. The energy splitting of 54 fine-structure levels, the oscillator strengths and transition probabilities for some strong dipole-allowed and intercombination transitions and the lifetimes of some fine-structure levels are presented and compared with available experimental and other theoretical values. Our lifetime for the 3s3p(P-1(0))3d(P-2(0)) level calculated in intermediate-coupling scheme, while differing significantly from our LS value, shows excellent agreement with the experimental result of Pinnington et al. In this calculation we also predict new data for several levels where no other theoretical and experimental results are available.