Two electron paramagnetic resonance spectra were obtained from samples which had been doped with Ag in a water vapor atmosphere. These centers (Si-NL56, Si-NL57) exhibited orthorhombic and trigonal symmetries, respectively, and an effective electron spin of S = ½. On the basis of studies using enriched Ag isotopes, and the analysis of an observed 2-fold hyperfine splitting, the participation of one Ag atom was established for both centers. The Si-NL56 center was identified as being an isolated substitutional Ag atom. Due to the presence of an additional hyperfine interaction with a nuclear spin of I = 5/2, the Si-NL57 spectrum was attributed to a complex of Ag with another impurity that had been introduced during diffusion. Upon taking account of the sample preparation procedure, the Si-NL57 center was attributed to an Als-Agi pair in a negative charge state.

P.N.Hai, T.Gregorkiewicz, C.A.J.Ammerlaan, D.T.Don: Physical Review B, 1997, 56[8], 4614-9