Photoelectron spectroscopy of some metals and alloys in the liquid state
Ultraviolet photoelectron spectroscopy measurements are presented from a variety of metals and alloys in the liquid state. For the metals, the optical density of states function is extracted from the photoemission data, by using an extended version of the three step model of Berglund and Spicer and compared to theoretical liquid density of states calculations based on a weak scattering approach which show only small deviations from the free electron parabola. The experimentally derived results for liquid lead and liquid tin reveal deviations from the simple picture with some of the solid state density of states features persisting into the liquid phase. By contrast, liquid lithium is shown to adhere more closely to the free electron model, showing a weaker deviation from the parabolic form for its experimentally derived density of states, while the same function for liquid silver is shown to be a smeared version of the solid state curve which, as explained, is not unexpected because of structural considerations. Photoemission data from liquid germanium is presented and discussed in comparison with published data for crystalline and amorphous germanium in terms of local atomic ordering. Data is presented from the liquid semiconducting lithium-lead alloy system and the similar lithium-tin alloy system which is shown incompatible with a simple ionic bonding model, and a stoichiometric structure is proposed where the unlike atom bonding is taken to be more covalent in character. Photoemission spectra are also presented from the silver- germanium alloy system which has a deep eutectic composition indicating enhanced glass forming qualities. Some change with composition can be seen in the valence band region but this cannot account for the above behaviour.