Nuclear Electric Field Gradient and Mean Square Displacement of the Iron Sites in Sodium Nitroprusside

Both the electric-field-gradient (EFG) and mean square displacement (MSD) tensor parameters at the Fe sites in sodium nitroprusside at 23°C have been determined with a high precision by the Mössbauer technique. The EFG asymmetry parameter is $\eta =0.01\mathrm{}\pm 0.01$. The principal axes of the two tensors do not coincide. Taking proper account of saturation effects was essential, even though the absorbers were only ∼0.2 mm thick. For the MSD, proper consideration of polarization effects was also important. A total of 34 runs on an absolutely calibrated mechanical drive gave for the quadrupole splitting $\Delta E_Q=1.7048\mathrm{}\pm 0.0025$ mm/sec.