Evaluation of the resonance oscillator strength of calcium

Configuration interaction wavefunctions are used to calculate the wavelength and oscillator strength (length and velocity forms) for the 4s 2 1 S to 4s4p 1 P o resonance transition in calcium. Good agreement between the velocity form and experiment is obtained. However, the length form overestimates the oscillator strength by approximately 10%. The dominant interactions which influence the transition under study are s 2 to d 2 and s 2 to ss' in the initial state and sp to dp and sp to s'p in the final state. The importance of including the non-fine-structure relativistic terms as well as the usual non-relativistic terms in the Hamiltonian in order to determine the configuration mixing is investigated. The importance of including core-valence correlation effects in the initial- and final-state wavefunctions is also investigated.