Calculating molecular Rydberg states using the one-particle Green's function:Application to HCO and C(NH_2)_3

摘要

A simple but accurate and computationally efficient method for routine ab initio calculations of molecular Rydberg states is described.The method,which can be applied to Rydberg states associated with a nondegenerate iori core,consists in the self-consistent solution of an effective one-electron problem.First,the restricted Hartree-Fock problem of the ion core is solved.The orbital energies and certain two-electron Coulomb matrix elements with respect to the molecular orbital basis are then used to construct an energy-dependent many-body correction to the Hartree-Fock mean field.This correction is derived from the Dyson equation satisfied by the one-particle Green's function.The method is applied to calculate Rydberg potential-energy curves of HCO.The presented data confirm and extend recent large-scale multireference configuration-interaction calculations and help develop a detailed theoretical description of the astrophysically important dissociative recombination of a low-energy electron with HCO~+.As further illustration of the utility of the method,the first ab initio calculations of the excited states of an electron bound to the guanidinium cation [C(NH_2)_3]~+ are reported.