Emission Characteristics of Silver Atoms in γ−Irradiated Organic Solid Solutions at 77 K

Abstract

Ag0 atoms were produced via the electron capture of Ag+ ions in γ-irradiated solid solutions of ethanol and MTHF at 77 K. The 2-dimensional time-resolved fluorescence spectra together with the steady-state fluorescence spectra and excitation spectra were measured by photoexcitation of Ag0 produced in the γ-irradiated solid solutions. The steady-state measurements have revealed the existence of two main emission bands at nearly 500 and 580 nm. The intensity of the 500 nm band increased and that of the 580 nm band concomitantly decreased with increasing concentration of Ag+ in both solutions. The time-resolved observation has shown that the 500 nm band consists of three components of different lifetimes (τ). The main component with τ ∼ 1 μs is attributed to the exciplex (Ag0·Ag+)*, the one with τ ∼ 2 μs, to the similar exciplex which is weakly coupled to solvent molecules, and the third one with τ ∼ 3 ns, to Ag0* trapped in a large cavity where Ag0 scarcely interacts with solvent molecules. The 580 nm band grows at about 0.5−1 μs and decays with a long lifetime, i.e., about 50 μs in ethanol or 40 μs in MTHF. The band is attributed to the exciplex (Ag0·L n )*, where L n denotes n solvent molecules.

ESR and Optical Properties of Copper Atoms in γ-Irradiated Organic Solutions at 77 K

“…In the case of Ag 0 in EtOH, the band at 400 nm (3.48 eV) was identified as the photoionization spectrum. The value of the ionization potential of Ag 0 in EtOH is reduced by the solvation energy in comparison with the value in gas phase, being calculated to be 3.2 eV with the estimated value of the solvation energy of − 4.6 eV . The value is close to the energy of the band at 400 nm.…”

“…The value of the ionization potential of Ag 0 in EtOH is reduced by the solvation energy in comparison with the value in gas phase, being calculated to be 3.2 eV with the estimated value of the solvation energy of -4.6 eV. 22 The value is close to the energy of the band at 400 nm. Since the solvation energy of Cu 0 in EtOH is estimated to be -2.4 eV, the ionization potential of Cu 0 in EtOH would be 5.6 eV.…”

“…Consequently, the absorption spectrum of Cu 0 may consist of several bands, being broadened and shifted depending on solvents in comparison with those in the gas phase and rare gas matrixes. In the same way as the case of Ag 0 in these solvents, we ascribe the bands from C 1 to C 5 to exciplexes formed between excited Cu 0 and ligands. It follows from Figures and that the ratio of the optical densities of the C 2 and C 3 bands to those of the C 4 and C 5 bands for the concentrated Cu + solutions is greater than that for the dilute solutions.…”

“…14 The dimer cation, Ag 2 + was found to form by the tunneling reaction between Ag 0 and Ag + ion at 77 K. [16][17][18][19] The optical properties of Ag 0 were previously studied in 2-methyltetrahydrofuran (MTHF), ethanol (EtOH), and aqueous solutions. [20][21][22] The absorption spectra of Ag 0 in EtOH and MTHF solutions consisted of the UV and NUV bands, each of which was composed of at least two bands. These bands were ascribed to Ag 0 originating from Ag + ions trapped in the cavities of different degrees of solvation.…”

Effects of UV Irradiation on ESR and Optical Properties of Cu(II) Ions in Organic Solid Solutions Containing CuCl at 77 K

“…As a fundamental research to elucidate the function and effects of metal ions and/or atoms in biological systems, we have been investigating the ESR and optical properties of 1B metal atoms produced radiation-chemically by reducing their mono cations in solid solutions [4][5][6][7][8][9][10][11][12]. In the series of our previous studies, formation of metal atoms, Cu 0 , Ag 0 and Au 0 in irradiated solid solutions containing their mono cations were evidenced by ESR spectra that exhibited duplicate quartets [10], duplicate doublets [8] and quartet [12], respectively.…”