0038-1098/84 $3.00 +.OO UNOCCUPIED BAND CRITICAL POINT ENERGIES OF NOBLE METALS DETERMINED WITH BREMSSTRAHLUNG ISOCHROMAT SPECTROSCOPY

We show that Bremsstrahlung Isochromat Spectroscopy (BIS) is a powerful and simple tool to determine unoccupied band critical point energies of solids. We determine some critical point energies of the noble metals and compare these to band structure calculations. We also determine the energy dependent lifetime broadening providing information about the imaginary part of the self energy corrections. ONE PARTICLE ENERGY band dispersion relations equipped with a large solid angle monochromator for and the influence of many body effects are of funda- AlKa! radiation (hw = 1486.7 eV) [ 11. The BIS electron mental importance for the understanding of physical gun is a cylindrical Pierce gun [2], producing a wedge properties of solids. Modern computational methods shaped beam with a rectangular cross section of 5 x have facilitated complete band structure calculations, 1.3 mm2 at the sample [3]. The polycrystalline Ag, Au the accuracy of which, as well as the validity of the one and Cu samples were cleaned in ultra high vacuum by electron approximations made, have been a subject of either scraping or argon ion etching. XPS was used to intense investigation. check for surface contamination. Experimental tools for studying band structres ar