Ab initio potential energy curves, transition dipole moments and spin-orbit coupling matrix elements for the first twenty states of the calcium dimer

State-of-the-art ab initio techniques have been applied to compute the potential energy curves of the calcium diatom in the Born-Oppenheimer approximation for the first twenty singlet and triplet states dissociating into 3P+ S-1, D-3+ S-1, D-1 + S-1 and P-1 + S-1 atomic states. All the excited state potential curves were computed using a combination of the linear response theory within the coupled-cluster singles and doubles framework for the core-core and core-valence electronic correlation with the full configuration interaction for the valence-valence correlation. The electric and magnetic transition dipole moments governing the X-1 Sigma(+)(g) -> 1 Sigma(+)(u), (1)Pi(u) and X-1 Sigma(+)(g)-> (1)Pi(g), respectively, have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Spin-orbit coupling matrix elements have been evaluated within the complete active space self-consistent field framework using an effective core potential from the Cowan-Griffin relativistic ab initio model potential method. With these couplings, the spin-orbit coupled potential energy curves for the 0(u)(+) and 1(u) states of the calcium diatom have been obtained. Our results are compared with other ab initio calculations and with the experimental data available for the calcium diatom.