Optical Transitions between Conduction Bands in Copper and Copper-Based Alloys

Abstract
An anomalous shift of the onset of interconduction-band optical absorption in copperaluminum alloys gives precise values for the direct and indirect energy band gaps, setting the upper-Q+ band profile in pure copper in the Fermi-surface-neck region of k space. In addition, it establishes the range of validity of a direct-transitions model. A consistent pattern of behavior is suggested among copper-based alloys with polyvalent solutes.