Time-Dependent Multiconfiguration Theory and Its Application to Ultrafast Electronic Dynamics of Molecules in an Intense Laser Field

Abstract

(spin-orbitals) as Φ(t )= P I CI (t)ΦI (t). The equations of motion (EOMs) for spin-orbitals in coordinate representation are derived together with the EOMs for configuration interaction coefficients CI (t). As an example of application to molecules, we presented the results of investigation of the ionization dynamics of H2 interacting with a near-infrared intense laser filed. By extending the concept of Hartree-Fock orbital energy to multiconfiguration theory, we newly introduced the molecular orbital of natural spin-orbitals (NSOs) {j} of a many-electron system and defined the orbital potentialsj(t) and correlation energies V c j (t) of NSOs. The total energy E(t) is decomposed into individual components as E(t )= P j ωj(t)¯ � j(t )a s in thermodynamics, whereωj(t) are the occupation numbers of {j} .W e proved that this type of partition of the total energy is interpreted as the time-dependent chemical potential for the two-electron system. The newly defined correlation energy V c j (t) associated with the j th NSO, involved inj(t), reflects dynamical electron correlations on the attosecond timescale. We also compared the energy ζj(t) directly supplied by the applied field with the net energy gain Δ¯ j (t) for respective natural orbitals. The responses of natural orbitals can be classified into three: Δ¯ j (t )= ζj (t) (spectator orbital); Δ¯ j(t) ζ j(t) (energy acceptor orbital). We found that ionization of H2 most efficiently occurs from a time-developing energy acceptor NSO 2σg for the case of the present applied field. We concluded that energy acceptor natural orbitals play a key role in ionization processes.