SILVER CLUSTERS - OPTICAL-ABSORPTION AND ESR-SPECTRA - STRUCTURE AND CALCULATION OF ELECTRON TRANSITIONS

The formation of Ag-3(2+) and Ag-4(+) clusters upon freezing out of aq ueous-alcohol glassy solutions of AgClO4 by gamma-irradiation at 77 K was established by ESR and optical spectroscopies. The Ag-3(2+) cluste r is formed by subsequent addition of Ag+ ions to a silver atom, and t he Ag-4(+) cluster is most probably formed by the reduction of the Ag- 4(2+) cluster by alcohol radicals. The energies of optical transitions and energy gaps for the Ag-4(m+) cluster (m = 0 to 3) were calculated . The absorption bands of the clusters shift to the UV region as the c harge increases, which agrees with the experimental results.