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 ab initio calculations by considering spin-orbit coupling (SOC). The potential energy curves (PECs) and spectroscopic constants of 12 Lambda-S states and 23 Omega states are calculated using the multi-reference configuration interaction plus Davidson correction method (MRCI + Q), which are in good agreement with the experiment. Based on the calculated SO matrix and the PECs of the Omega states, the interaction between the d(3)pi 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 d(3)pi(0+)-X-1 Sigma(+)(+0), d(3)pi(1)-X-1 Sigma(+)(0+), and a(3)Sigma(+)(1)-X-1 Sigma(+)(0+) are studied. Our results indicate that the previously observed spectra of GeCl+ in the 290-325 nm range should be assigned as the a(3)Sigma(+)(1)-X-1 Sigma(+)(0+) transition. Moreover, the predissociation behavior of the d3 pi state between the vibrational levels v ' = 1 and v ' = 10 is discussed, and the radiative lifetimes of transitions d(3)pi(0+)-X-1 Sigma(+)(0+) and d(3)pi(1)-X-1 Sigma(+)(0+) are evaluated on the order of microseconds, while a(3)Sigma(+)(1)-X-1 Sigma(+)(0+) is on the order of milliseconds. We estimate that the strongest bands of a(3)Sigma(+)(1)-X-1 Sigma(+)(0+) 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.