The prominent 5d-orbital contribution to the conduction electrons in gold.

We have examined the valence-band electronic structures of gold and silver in the same column in the periodic table with nominally filled d orbitals by means of a recently developed polarization-dependent hard x-ray photoemission. Contrary to common expectation, it is found that the 5dorbital electrons contribute prominently to the conduction electrons in gold, while the conduction electrons in silver are to some extent free-electron-like with negligible 4d contribution, which could be related to the well-known fact that gold is more stable than silver in air. The 4d electron correlation effects are found to be essential for the conduction electron character in silver. [ABSTRACT FROM AUTHOR]