Calibration of the isomer shift and measurement of ΔRR for the 13-keV Mössbauer transition of Ge73

The first isomer shifts of the 13-keV Ge73 Mössbauer transition are reported. Shifts are observed in Cu and in GaAs. The shift of Ge in GaAs versus Ge is interpreted in terms of a calculation by Pickett et al. of the bonding at a (110) Ge-GaAs interface. From this and a calculation by Nestor et al. of electron density at the Ge73 nucleus we measure ΔRR=+0.45(2)×10-3. Shell-model calculations of the nuclear size change by Uher predict ΔRR=+0.50×10-3. The Ge:Cu shift indicates s-electron transfer from Cu to substitutional Ge.