Modeling LiH potential-energy curves: An approach based on integration in finite space

Abstract

In this paper, we introduce a finite-space integration method to shed physical insight into the interactions of a Rydberg electron with a molecular ion core, as sampled by the potential-energy curves (PECs) of various electronic states of LiH. We postulate that these interactions are dominated by two independent electron-atom processes: (1) scattering of the Rydberg electron at negative energy solely off of the lithium atomic core and (2) a transition from the lithium scattering state to the lithium valence orbital necessarily accompanied by an excitation of the hydrogen atom. It is shown that the ratio of the amplitudes for the occurrences of these two processes can be obtained by means of bounded integrations inside a small region of space where the electron-electron repulsion term in the Hamiltonian is dominant. Our theory and approximations are verified by a comparison of derived potential-energy curves with those produced by ab initio calculations as well as another empirical model that uses the Fermi approximation. It is observed that the complicated features of the PECs, which reflect the nodal structure of the Rydberg orbitals, are reproduced well within our treatment.