Energies, electric dipole (E1), quadrupole (E2), octupole (E3) and magnetic dipole (M1), quadrupole (M2) transition rates for Ca XII, Ti XIV, Cr XVI, Fe XVIII and Ni XX

Energies, weighted oscillator strengths (gf), line strengths (S) and radiative rates (A) for allowed and forbidden transitions are presented for 2s2p62S1/2 ? 2s22p52P1/2, 2P3/2 and 2s22p52P1/2 ? 2s22p52P3/2 transitions in fluorine-like Ca XII (Z = 20), Ti XIV (Z = 22), Cr XVI (Z = 24), Fe XVIII (Z = 26) and Ni XX (Z = 28) ions. Moreover, the allowed electric dipole (E1) and the forbidden electric quadrupole (E2), octupole (E3), magnetic dipole (M1) and quadrupole (M2) transition rates for some transitions are obtained. The 2s22p5–2s 2p6-type transitions of F-like ions are prominent in high-temperature plasmas and are useful for diagnostics. The present results are obtained from configuration interaction atomic structure calculations using the code SUPERSTRUCTURE (SS) which includes relativistic effects in Breit–Pauli approximation. The comparison of the present energies with the available observed energies displayed very good agreement (< 1%). The presented excitation energy results have been compared with other detailed relativistic approaches such as Dirac–Fock, coupled cluster and configuration interaction for a few ionic states. © 2019, Indian Association for the Cultivation of Science.