Induction of optical transitions through complexation within Hg-rare gas van der Waals systems

The high repulsive states of HgAr and HgNe van der Waals complexes, correlating with Hg 6s6d atomic states have been investigated by double resonance spectroscopy, through the first excited state A ³0 ⁺ and B ³1 of the complexes. The repulsive potentials have been fitted through numerical Franck-Condon simulations. They have been characterized by perturbative calculation as quasi-pure 6dΣ potentials in Hund's case a. The strong Hg-rare gas electrostatic interaction potential overruns the spin-orbit interaction at distances shorter than 7 Å. These observed repulsive states are mostly of Ω=1 character correlating with ³D₃ at infinite distances. The contribution from the potential of Ω=0^- symmetry correlating with ¹D ₂ is of minor importance. Therefore, the absorption in the repulsive states of the complex arises mostly from proximity induced absorption in an optically forbidden transition ³P₁→³D ₃. A perturbative model accounts well for the bound free absorption intensities experimentally observed.