Double-electron excitation channels at the L edges of atomic Hg

X-ray-absorption measurements at the L3, L2, and L1 edges of Hg vapor have been performed using synchroton radiation. The onset of multielectron excitation channels involving 2p (or 2s) and 4f electrons has been revealed. The experimental onset energies are compared with self-consistent-field Dirac-Fock (SCF-DF) calculations and Z+1 estimates, which, in this specific case, were inaccuracte. The importance of these features in x-ray-absorption fine-structure structural data analysis for sixth-period elements is addressed, and the SCF-DF onset energies, covering the elements Hf-Rn, are presented.