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 Au-Ga alloys have bee n 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 wi th values published for an Au-Al alloy. Backtransfer for s-electrons f rom Ga to Au is evident from X-ray photoelectron spectroscopy and conf irms an sd hybrid bond in this alloy system. On melting, this bond per sists in the molten state, but with diminished effect which is evident from the reduced coordination number obtained from EXAFS. A similar b ond is found in molten AuSn, but not in an Au-Ge alloy.