Modified operator perturbation theory computational approach to atomic systems in a DC electric field: Stark resonances

New computational realization of the modified operator perturbation theory method to computing the Stark resonances energies and widths for the non-hydrogenic (non-H) atomic systems in a DC electric field is presented. The method is based on the operator form of the perturbation theory of the Schrödinger equation for the non-H atomic systems and includes the physically reasonable distorted-waves approximation in the frame of the formally exact quantum-mechanical procedure. The Stark resonances energies and widths in the lithium atom are calculated and compared with results of calculations on the basis of the method of complex eigenvalue Schrödinger equation by Themelis-Nicolaides, the complex absorbing potential method by Sahoo-Ho and the B-spline-based coordinate rotation method approach by Hui-Yan Meng et al.