Generalizations of the multiconfigurational time-dependent Hartree–Fock approach

Abstract

We extend and generalize the time-dependent Hartree–Fock (TDHF) and multiconfigurational time-dependent Hartree–Fock (MCTDHF) approaches so that electronic transition energies from non-singlet reference states to states of pure spin symmetry other than the reference state can be described. Initial calculations are presented for the Be atom using the (2s3s)³S state and the (2s²)¹S state as reference states. The accuracy of the calculated excitation energies is examined as a function of extending the active space of the MCSCF reference state. Close agreement between the excitation spectra as obtained from either of the reference states is obtained when inner–outer correlation effects are considered in the MCSCF reference state.