Aqueous, 2-methyltetrahydrofuran, and ethanol solutions
containing Ag+ were irradiated at 4 or 77 K
with
γ-rays. The main absorption bands observed in the region of
350−450 nm for these solutions are ascribed
to Ag0. The absorption bands consist of several
components, which are ascribed to Ag0 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 Ag0 in solid rare gases, we
tentatively ascribe the bands near 300 nm to
Ag0
trapped in a large cavity in which shell structure consists of C−H
groups.
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.
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