Rare Earths. Iv. Dissociation Energies of the Gaseous Monoxides of the Rare Earths

摘要

The dissociation energy of the gaseous rare earch monoxides together with the closely related compounds ScO and YO were determined from Knudsen effusion and mass spectrometric isomolecular oxygen-exchange reaction studies. It is shown that there is a double periodicity in the variations of the dissociation energies with atomic number and that these variations closely match those of the heats of sublimation of the rare earth metals. Assuming a common bound state for the monoxides, M++O--, it is shown that the variations in the dissociation energies in the lanthanide series correspond to the magnitude of the 4f(n) to 4f(n-1)5d transitions of the divalent ions. (Author)9