ESR and optical properties of copper atoms in gamma-irradiated organic solutions at 77 K

EtOH and MTHF solutions containing Cu+ ions are gamma -irradiated at 77 K. ESR spectra are attributed, for the first time, to Cu-0 that is produced ra diation-chemically by reducing Cut ions in the solutions at 77 K. A large d elocalization of the unpaired spin density of Cu-0 onto ligands is deduced. No evidence for formation of the dimer cation of Cu-0 has been obtained. T his is contrary to the case of Ag-0 produced in the solutions containing Ag + ions. The NUV absorption spectrum of Cu-0 is decomposed into five Gaussia n bands that are attributed to two types of exciplexes formed between excit ed Cu-0 and ligands: one associates with Cu+ ions as well as solvent molecu les, the other consists mainly of solvent molecules. The exciplexes are sup posed to be transferred to relaxed states followed by two emission bands, o ne of which is common to both solvents and the other is characteristic of t he solvents. The absorption band at 255 nm is ascribed to a photoionization spectrum of Cu-0.