Nobumitsu Honjou

Ab initio configuration interaction study on the electronic structure of the X2Σ+, B2Σ+ and 32Σ+ states of SiO+

The energy levels and electronic structure of the X2Σ+, B2Σ+ and 32Σ+ states of SiO+ are studied using ab initio configuration interaction (CI) calculations at and around their equilibrium internuclear distances R e. Spectroscopic constants and the vertical excitation energy from the SiO+ X2Σ+ state are predicted for the 32Σ+ state. Based on the calculated CI wavefunctions, avoided crossings of the potential energy curve for the 32Σ+ state and a near-degeneracy effect in the avoided crossing region are examined. The effects of the mixing of excited configuration state functions in the total electronic wavefunctions for the 1–3 2Σ+ states are investigated by analysing correlation energies in terms of the contributions from classes of excited configurations. The importance of both the near-degeneracy effect and the correlation energy effect in describing correctly the electronic structure of the 3 2Σ+ state in the neighbourhood of its R e is discussed.

Ab initio study on the electronic structure of the 4 2Σ+ and 5 2Σ+ excited states of CO+

Abstract The electronic structure of the 4 2 Σ + and 5 2 Σ + excited states of CO+ are studied by using state-averaged complete-active-space self-consistent-field/multireference and configuration interaction calculations at and around the equilibrium internuclear distance Re = 2.132 au of the CO 1 Σ + ground state. The results reveal that the 4 2 Σ + and the 5 2 Σ + state are located at 16.0 and 18.6 eV above the CO + 2 Σ + ground state at Re = 2.132 au, respectively. The 5 2 Σ + state in the internuclear distance region R = 1.930−2.132 au and the 4 2 Σ + state around R ≈ 1.850 au are identified as the lowest Rydberg-type 2 Σ + state. This state has a predominant Rydberg-type configuration 4σ26σ1π4 which is composed of a C2+O ion core (4σ21π4) plus one electron in an s-type Rydberg orbital (6σ).

Ab initio configuration interaction study on the electronic structure of the 1–42Π states of SiO+ and the avoided crossings of the 2–42Π potential energy curves

Ab initio configuration interaction (CI) calculations have been carried out to study the energetics and electronic structure of the 1–42Π states of SiO+ and the avoided crossings of the 2–42Π potential energy curves (PECs). Spectroscopic constant values are predicted for the experimentally unknown 2–42Π states. Two avoided crossings, one between the 2–32Π PECs and the other between the 3–42Π PECs, are found to have a marked characteristic of a small minimum energy difference between the relevant PECs; 0.12eV for the former and 0.04 eV for the latter. Each small minimum energy difference results principally from the lack of direct interaction between two main configuration state functions (CSFs) in the CI wavefunctions for the two 2Π states concerned, since the off-diagonal CI matrix element between the two main CSFs vanishes identically. The reasons for both the vanishing and the non-vanishing CI matrix elements in terms of the CSFs, which are important for the description of the two avoided crossings, are explained from the standpoints of the Slater-Condon rules and symmetry properties of the important CSFs. The main CSFs mix through the direct interactions with intermediary CSFs, representing the near-degeneracy effect resulting in the avoided crossing.