Time-dependent complete-active-space self-consistent field method for multielectron dynamics in intense laser fields

摘要

The time-dependent complete-active-space self-consistent-field (TD-CASSCF)method for the description of multielectron dynamics in intense laser fields ispresented, and a comprehensive description of the method is given. Itintroduces the concept of frozen-core (to model tightly bound electrons with noresponse to the field), dynamical-core (to model electrons tightly bound butresponding to the field), and active (fully correlated to describe ionizingelectrons) orbital subspaces, allowing compact yet accurate representation ofionization dynamics in many-electron systems. The classification into thesubspaces can be done flexibly, according to simulated physical situations anddesired accuracy, and the multiconfiguration time-dependent Hartree-Fock(MCTDHF) approach is included as a special case. To assess its performance, weapply the TD-CASSCF method to the ionization dynamics of one-dimensionallithium hydride (LiH) and LiH dimer models, and confirm that the present methodclosely reproduces rigorous MCTDHF results if active orbital space is chosenlarge enough to include appreciably ionizing electrons. The TD-CASSCF methodwill open a way to the first-principle theoretical study of intense-fieldinduced ultrafast phenomena in realistic atoms and molecules.