Optical absorption properties of silver atoms in gamma-irradiated aqueous, 2-methyltetrahydrofuran, and ethanol solutions at low temperatures

Aqueous, 2-methyltetrahydrofuran, and ethanol solutions containing Ag+ were irradiated at 4 or 77 K with gamma-rays. The main absorption bands observed in the region of 350-450 nm for these solutions are ascribed to Ag-0. The absorption bands consist of several components, which are ascribed to Ag-0 trapped in cavities with different structures. As the annealing temperature was raised, the bands at the shorter wavelengths became predominant in the aqueous solution. In addition to the main absorption bands, two or three absorption bands were observed in the vicinity of 300 nm for the solutions other than the aqueous solution at 77 K. In comparison with the spectra of Ag-0 in solid rare gases, we tentatively ascribe the bands near 300 nm to Ag-0 trapped in a large cavity in which shell structure consists of C-H groups.