Knowledge Bank

Ab initio pseudopotential calculations have been carried out for the series of holmiumcontaining species in order to provide an assignment of the bands observed in UV-visible spectra of matrix isolation experiments. The formation of the pure holmium as well as the mixed holmium-silver clusters is expected under the experimental conditions, and the following species have been considered theoretically: $Ho2,Ho3,Ag2,Ag3,AgHo,Ag2Ho,AgHo2$. The configuration interaction calculations with single and double excitations have been applied to estimate the transition energies and transition moments. The Stevens-Basch-Krauss pseudopotential and the corresponding basis set have been used for silver. Two sets for the holmium pseudopotential and basis function parameters borrowed from the Stuttgart group tables have been employed. Namely, the search of the equilibrium geometry configurations of the holmium-containing clusters has been performed at the Hartree-Fock level with the $Q=11$ pseudopotential, describing the holmium atom in the $4f106s25d1$ electronic state, and the calculations of the energy levels for the established geometries have been carried out with the $Q=10$ pseudopotential corresponding to the true $4f116s2$ atomic configuration. A single empirical correction parameter has been introduced for the predicted band positions in the electronic spectra when taking into account the firmly established results for the matrix-isolated species $Ag,Ho,Ag2,Ag3$. With such a correction, the computed wavelengths for the strong bands in the spectra of $Ho2$ (500 nm) and AgHo (432 nm) are in excellent agreement with the tentative experimental assignments 498/504 nm for $Ho2$ and 430 nm for AgHo. No theoretical support has been provided for the formation of metal trimers in the experiments.