Configuration-interaction-based time-dependent orbital approach for ab initio treatment of electronic dynamics in a strong optical laser field

The time-dependent configuration interaction singles (TDCIS) method—an ab initio electronic-structure technique with predictive character—is reformulated in terms of an effective one-electron theory with coupled channels. In this form, the TDCIS equations of motion may be evaluated using standard wave-packet propagation techniques in real space. The time-dependent orbital formulation of TDCIS has computational and conceptual advantages for studying strong-field phenomena in many-electron systems. A simplified version of this theory, referred to as the determinantal single-active-electron (d-SAE) method, is derived. TDCIS and d-SAE are tested by their application to a one-dimensional two-electron model in a strong laser field. The numerically exact time-dependent dipole moment of the interacting system is found to be very well reproduced with TDCIS. The d-SAE method is less accurate, but still provides superior performance in comparison to the standard single-active-electron approach.

Figure 1

(Color online) Comparison of the dipole moment of the exact 1D helium model (solid line) and the dipole moment calculated using the d-SAE approximation [Eqs. (46, 47)]. The three different one-electron potentials $V_{\mathrm{mod}}$ (dashed line), $V_{\mathrm{HF}}$ (dashed-dotted line), and $V_{\mathrm{KS}}$ (dotted line) employed in the d-SAE calculation are explained in the text.

Figure 2

(Color online) Time evolution of the dipole moment of the 1D helium model. Comparison of s-SAE [Eqs. (1, 2)] and d-SAE [Eqs. (46, 47)]. The one-particle potential used is $V_{\mathrm{HF}}$ [Eq. (52)].

Figure 3

(Color online) Comparison of the dipole moment of the exact 1D helium model, TDCIS, d-SAE (with $V_{\mathrm{HF}}$), and TDHF. The TDCIS dipole moment is almost indistinguishable from the exact result.