Spectroscopic Properties and Spin-Orbit Coupling of Electronic Excited States of GeCl.

The electronic structure and spectroscopic properties of GeCl are studied by high-level calculations by considering spin-orbit coupling (SOC). The potential energy curves (PECs) and spectroscopic constants of 12 Λ-S states and 23 Ω states are calculated using the multi-reference configuration interaction plus Davidson correction method (MRCI + ), which are in good agreement with the experiment. Based on the calculated SO matrix and the PECs of the Ω states, the interaction between the dΠ state and other states caused by the SOC and the double-potential well structure caused by the avoided crossing rule and the properties of transitions dΠ-XΣ, dΠ-XΣ, and aΣ-XΣ are studied. Our results indicate that the previously observed spectra of GeCl in the 290-325 nm range should be assigned as the aΣ-XΣ transition. Moreover, the predissociation behavior of the dΠ state between the vibrational levels ' = 1 and ' = 10 is discussed, and the radiative lifetimes of transitions dΠ-XΣ and dΠ-XΣ are evaluated on the order of microseconds, while aΣ-XΣ is on the order of milliseconds. We estimate that the strongest bands of aΣ-XΣ are the 0-16, 0-17, and 0-18 bands. This study will promote our understanding of the detailed electronic structure and spectra of the GeCl radical cation.