XANES and EXAFS investigation of sd hybrid bonds in alloys of gold with gallium, germanium and tin through the solid-liquid transition

The XANES for the Au L_III edge in solid Au and AuGa alloys have been measured using synchrotron radiation. The excess white line areas in the alloys have been compared with the same region of pure Au to give the d-state charge transfer from Au to Ga. It is in good agreement with values published for an AuAl alloy. Backtransfer for s-electrons from Ga to Au is evident from X-ray photoelectron spectroscopy and confirms an sd hybrid bond in this alloy system. On melting, this bond persists in the molten state, but with diminished effect which is evident from the reduced coordination number obtained from EXAFS. A similar bond is found in molten AuSn, but not in an AuGe alloy.