Silver clusters: Optical absorption and ESR spectra; structure and calculation of electron transitions

The formation of Ag₃ ²⁺ and Ag₄ ⁺ clusters upon freezing out of aqueous-alcohol glassy solutions of AgClO₄ by γ-irradiation at 77 K was established by ESR and optical spectroscopies. The Ag₃ ²⁺ cluster is formed by subsequent addition of Ag⁺ ions to a silver atom, and the Ag₄ ⁺ cluster is most probably formed by the reduction of the Ag₄ ²⁺ cluster by alcohol radicals. The energies of optical transitions and energy gaps far the Ag₄ ^m+ cluster (m = 0 to 3) were calculated. The absorption bands of the clusters shift to the UV region as the charge increases, which agrees with the experimental results.