The room-temperature irradiation of Rh3+-doped emulsion powders led to the production of 3 paramagnetic Rh2+-related centers (R4, R5, R6). A combined X- and Q-band electron paramagnetic resonance and electron nuclear double resonance study permitted the derivation of an almost complete structural model for these centres. In the X-band electron nuclear double resonance spectra of R4 and R5, interactions of the unpaired electron with nearby protons were identified. This indicated that, for these centers, Cl− ligands were exchanged for H2O or OH−. The R6 centre, identified as being a (RhCl6)4− complex, was fundamentally different to the predominant centre in large Rh2+-doped melt-grown single crystals.

Magnetic Resonance Study of Rh Complexes in AgCl Microcrystals. H.Vrielinck, K.Sabbe, F.Callens, P.Matthys, D.Vandenbroucke: Spectrochimica Acta A, 2000, 56[2], 319-29