Reinvestigation of the electronic spectroscopy of the Au–Ar complex

The Au–Ar complex is reinvestigated employing resonance-enhanced multiphoton ionization spectroscopy. Spectra are reported, corresponding to the atomic transition Au(6p←6s). This electronic excitation yields Π2 and Σ+2 states of Au–Ar, which interact under the influence of spin-orbit coupling. The spectra are consistent with strong σ-π mixing induced by the large spin-orbit coupling of Au, leading to strong interaction of the two Ω=1∕2 states, which arise from the Ar(S01)+Au(P1∕2,3∕22) asymptotes, and the consequent formation of a “shelf” on the outer wall of the lowest Ω=1∕2 state. In addition, high-level ab initio calculations are reported on the ground electronic state, XΣ+2, including extrapolation to the basis set limit.