Spectroscopic properties and spin–orbit coupling of electronic excited states of the germanium dimer

Abstract

The electronic structure and spectroscopic properties of the germanium dimer have been investigated by high-level ab initio calculations with consideration of spin–orbit coupling (SOC). The potential energy curves (PECs) of 19 Λ–S states, as well as those of 52 Ω states generated from the Λ–S states, are calculated by the multireference configuration interaction plus Davidson correction (MRCI + Q) method. The properties of the F³Σ⁺_u1−X³Σ⁻_g1 and H³Σ⁻_u1−X³Σ⁻_g1 transitions as well as the interactions of the F³Σ⁺_u and H³Σ⁻_u states with other excited states induced by SOC are investigated based on the calculated SO matrix and the PECs of the Ω states. Our results indicate that the previously observed spectra of Ge₂ in the range 20 500–22 000 cm⁻¹ should be assigned as the transition between the Ω = 1_g component of the X³Σ⁻_g state and Ω = 1_u of the F³Σ⁺_u state. Moreover, owing to the strong SOC with the repulsive 2⁵Π_u state, the H³Σ⁻_u state is predissociative, leading to the Ge(³P₂) + Ge(³P₁) channel at vibrational levels higher than v′ = 6. Our theoretical study would provide comprehensive information and shed light on understanding the spectroscopy and dynamics of the electronic excited states of Ge₂.