Energy levels, transition probabilities, and lifetimes have been determined for all levels of the Ca I spectrum up to $3d4p{}^1{F}_3^o$ using the multiconfiguration Hartree-Fock method with lowest-order relativistic effects included through the Breit-Pauli Hamiltonian. The mixing of singlet and triplet configuration states was found to be considerably stronger in $4s5p{}^{1,3}{P}_1^o$ levels than in $4s4p{}^{1,3}{P}_1^o$ levels. The near degeneracy of the nonrelativistic $3d4p{}^3{F}^o$ and ${}^1{D}^o$ term energies, differing by only $39.59{\mathrm{cm}}^{-1}$ resulted in highly mixed Breit-Pauli levels for $3d4p{}^3{F}_2^o$ and ${}^1{D}_2^o.$ Some intercombination transitions from these levels have transition probabilities of magnitude similar to weaker spin-allowed transitions. The “fine-tuned” transition probability for the $4s4p{}^3{P}_1^o-4s4d{}^1{D}_2$ transition was found to be $1.53\times {10}^3{\mathrm{s}}^{-1},$ in agreement with a quenching rate observed in a doppler cooling experiment [Binnewies et al., Phys. Rev. Lett. 87, 123002 (2001)].

• Received 19 March 2003

DOI:https://doi.org/10.1103/PhysRevA.68.012507