An ENDOR study was made of electrons which were shallowly trapped at [Fe(CN)6]4- complexes in doped AgCl emulsions. This revealed that the dopant replaced an [AgCl6]5- lattice unit without any additional lowering of the local symmetry and without associated charge-compensating cationic vacancies. This conclusion was supported by the experimentally deduced Bohr radius (1.85nm) for the shallow electron center, which was only slightly larger than that reported for the Pb2+-related shallow electron center in AgCl. A deviation from the usual cusp-less envelope function in the region near to the [Fe(CN)6]4- dopant was attributed to the covalent nature of the AgCl lattice. Effects which arose from the grain structure appeared to interfere with the interpretation of the results from 13C-enriched [Fe(CN)6]4--doped emulsions, in which an ensemble of slightly different electron centers was believed to exist. The possible interfering artefacts were suggested to include surface effects, weak associations with impurities and/or with distant Ag-ion vacancies, and structural inhomogeneities which were introduced into the microscopic grains during precipitation.

M.T.Bennebroek, J.Schmidt, R.S.Eachus, M.T.Olm: Journal of Physics - Condensed Matter, 1997, 9[15], 3227-40