Analysis of the matrix induced changes in the optical spectra of matrix isolated noble metal atoms

Abstract

The absorption spectra of the noble metal atoms Cu, Ag, and Au isolated in Ar, Kr, and Xe matrices have been measured as a function of matrix temperature in the range between 3 K and about 0.4 of the respective matrix triple point temperature. The spectra show a pronounced energy shift of the absorption peaks with temperature which is entirely reversible in well annealed matrices in the above-given temperature range. These spectra were evaluated by crystal field arguments to obtain more direct information on the matrix influence, which is discussed in terms of difference in level shifts, change in spin–orbit splitting, and crystal field splitting. The results are then explained by a model in which the matrix atoms are treated as clouds of negative charge which introduce a repulsive potential in the region of the metal electrons when the metal atom is squeezed into the matrix cage. The change with temperature in the interaction between metal atom and matrix is discussed in detail. In addition, an unambiguous assignment of the optical transitions under consideration has been made for the metal atoms in the crystal field of the matrix.