where Z A is the atomic number and R A are the spatial coordinates of nucleus A, r and r ′ are the electronic spatial coordinates, and Vext is an external, time-dependent potential applied to the system that couples with the electronic motion. The exact solution of TDSE is often impractical except for systems with a small number of electrons and one can proceed towards an approximate solution by assuming that Ψ e can be described by a single Slater determinant built from a set of N one-electron orbitals in an N -electron system (this is the case in the Kohn-Sham and the Hartree-Fock formalisms). This approximation may be inadequate to describe effects of strong electron correlation and can be rectified by incorporating multiple determinants into the wave function (as in the configuration interaction formalism). The methods used in the present study, TDCIS and real-time TDHF (RT-TDHF), share the restricted Hartree-Fock (RHF) wave function as their ground state. The two methods have been shown to exhibit similar time-dependent behavior in some cases. However, there are some key differences between the two methods in terms of how they incorporate the time-dependence of electronic motion, outlined in the following sections.