Stark resonance parameters for the 3a₁ orbital of the water molecule

The Stark resonance parameters for the 3a ₁ molecular orbital of H₂O are computed by solving a system of partial differential equations in spherical polar coordinates. The starting point of the calculation is the non-spherical quantum potential derived for this orbital from a single-center expanded Hartree–Fock orbital. The resonance positions and widths are obtained after applying an exterior complex scaling technique to describe the ionization regime for external fields applied along the two distinct $\hat{z}$ directions associated with the symmetry axis. Comparison is made with previous results for the 1b ₁ and 1b ₂ orbitals obtained from a spherical potential approximation. (paper)