Emission and excitation spectra of silver atoms in γ-irradiated aqueous, ethanol, and 2-methyltetrahydrofuran solutions at 77 K

Abstract

Silver atoms (Ag°) were produced by γ-irradiation of frozen aqueous, ethanol and 2-methyltetrahydrofuran (MTHF) solutions containing Ag + at 77 K. Emission and excitation spectra of Ag° were measured at this temperature for these solutions. Aqueous solutions did not emit appreciably. Ethanol and MTHF solutions showed two emission bands centered at nearly 500 and 600 nm, which had short and long lifetimes, respectively. The intensity ratios for the two bands, i.e. I 500/ I 600 were found to decrease with increasing excitation wavelength. The excitation spectra of Ag° in ethanol at 77 K showed that the threshold wavelengths for both emission bands are 360 nm. However, the threshold wavelengths for 500 and 600 nm bands are 360 and 400 nm, respectively, in MTHF. The ionization potentials of Ag° in these solutions were estimated from the Born equation. The observed results can be explained in terms of the photoionization of excited Ag°, and the formation of fluorescent complexes consisting of excited silver atoms and solvent molecules.