Configuration interaction study on electronic structures and transitional properties of excited states of GeO molecule

Abstract

GeO molecule, which plays an important role in fabricating integrated optics and semiconductor components, has received much attention. However, the electronic state density of the molecule is very large, and the electric structures and transitional properties of the molecule have not been well investigated. In this work, the 18 Λ -S states correlated to the lowest dissociation limit (Ge(3Pg)+O(3Pg)) are calculated by a complete active space self-consistent field (CASSCF) method, through using the previous Hatree-Fock molecular orbitals as the starting orbitals. Furthermore, we take all configurations in the configuration interaction expansions of the CASSCF wave functions as a reference configuration, and calculate the energies of the 18Λ-S states by a high-level multireference configuration interaction method. The core-valence correlation effect of the 3d orbit of Ge atom, the scalar relativistic effect, and the Davidson correction are taken into consideration in the calculations. On the basis of the calculated potential energy curves of the bound and quasibound electronic states, the spectroscopic constants (Re, Te, ωe, ωeχe, and Be), vibrational energy levels, vibrational wave functions, and Franck-Condon factors (FCFs) are obtained by solving the radical Schrödinger equation. The computed spectroscopic constants of these electronic states are well consistent with previously available experimental results. We calculate the electric dipole moments of electronic states with different bound lengths, and analyze the influences of the variation of electron configuration on the electric dipole moment. The calculated potential energy curves indicate that the adiabatic transition energies of A1Π, 11Σ-, D1Δ, a3Π, a’3Σ+, d3Δ, and e3Σ- sates are located in a range of 26000-37000 cm-1, and the spin-orbit coupling of the states can obviously affect the corresponding vibrational wave functions. With the help of calculated spin-orbit coupling matrix elements, the perturbations of the nearby states to a3Π and A1Π are discussed in detail. Our calculation results indicate that the spin-orbit coupling between A1Π and e3Σ- states has an evident perturbation on the v’> 4 vibrational levels of A1Π, and the v’≥ 0 vibrational levels of a3Π state are perturbed by the crossing states a’3Σ+, d3Δ, e3Σ-, 11Σ-, and D1Δ. On the basis of computed transition dipole moments and FCFs of A1Π-X1Σ+ and A’1Σ+-X1Σ+ transitions, the radiative lifetimes of the six lowest vibrational levels of the two singlet excited states are computed.