Calculation of Stark resonance parameters for valence orbitals of the water molecule

An exterior complex scaling technique is applied to compute Stark resonance parameters for two molecular orbitals (1b(1) and 1b(2)) represented in the field-free limit in a single-center expansion. For electric dc field configurations that guarantee azimuthal symmetry of the solution the calculation is carried out by solving a two-dimensional partial differential equation in spherical polar coordinates using a finite-element method. The resonance positions and widths as a function of electric field strengths are shown for field strengths starting in the tunneling ionization regime and extending well into the over-barrier ionization region.