Experimental radiative lifetimes for highly excited states and calculated oscillator strengths for lines of astrophysical interest in singly ionized cobalt (Co ii)

This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions of astrophysical interest in singly ionized cobalt. More precisely, 19 radiative lifetimes in Co⁺ have been measured with the time-resolved laser-induced fluorescence technique using one- and two-step excitations. Out of these, seven belonging to the high lying 3d⁷(⁴F)4d configuration in the energy range 90 697-93 738 cm^-1 are new, and the other 12 from the 3d⁷(⁴F)4p configuration with energies between 45 972 and 49 328 cm^-1 are compared with previous measurements. In addition, a relativistic Hartree-Fock model including core-polarization effects has been employed to compute transition rates. Supported by the good agreement between theory and experiment for the lifetimes, new reliable transition probabilities and oscillator strengths have been deduced for 5080 Co ii transitions in the spectral range 114-8744 nm.