Gold-metal dissociation energies measured by mass-spectroscopic methods in 1967 by Gingerich and co-workers showed unexpectedly high ${\mathit{D}}_{\mathit{e}}$ values compared with those of the corresponding copper and silver compounds. In the past, this has been explained in terms of the increased ionicity of the diatomic gold compounds on the basis of the Pauling model. In fact, the very high dissociation energies observed for AuLa and AuLu arise from relativistic effects, as shown by calculations of nonrelativistic and relativistic configuration interactions. The expected overall trend in the group-11 series is also explained (bond stabilities: AuM≫CuM>AgM, M any metal atom) in terms of relativistic effects and new spectroscopic data are given for AuLa and AuLu.

• Received 23 April 1990

DOI:https://doi.org/10.1103/PhysRevA.43.1644