Calculations of S--P transition energies and oscillator strengths in few-electron atoms and ions

First-principle calculations of transition energies in atoms with accuracy that matches high-resolution spectroscopic measurements is a challenging task. For few-electron atoms (n=2-6), however, this can be done within the framework of the variational method augmented with the use of all-particle explicitly correlated Gaussians (ECGs) and the perturbation theory for treatment of leading relativistic and quantum electrodynamics effects. In this talk I will consider several low-lying S and P states of lithium, beryllium, and carbon ion and demonstrate the current capabilities of the approach. I will also talk about the calculations of dipole moments and oscillator strengths corresponding to S--P transitions.