Excitation energies and oscillator strengths of Ca I using multireference many-body perturbation theory

Excitation energies and oscillator strengths of neutral calcium (Ca I) are calculated through third order using a variant of the multireference many-body perturbation theory, known as the effective valence-shell Hamiltonian ${(H}^v)$ method. Transition energies, oscillator strengths, and binding energies of various states are computed and compared with experimental and other theoretical data. These quantities are in favorable agreement with the experiment and other correlated calculations. The basis and valence space dependence of the $H^v$ scheme are addressed with some illustrative examples.