Calorimetric optical absorption measurements at 4.2°K have been made on a representative series of $\alpha$ brasses over the wavelength range 0.23 to 4.0 microns using electropolished bulk specimens. Changes in the absorption spectrum below 6000 A are interpreted in the light of current theories concerning the band structure of noble metal alloys. The variation of the infrared absorptivity with residual resistivity shows that the impurity relaxation time for copper is anisotropic. This anisotropy increases on alloying and suggests that the Fermi surface becomes more distorted with increasing solute concentration.

• Received 22 April 1959

DOI:https://doi.org/10.1103/PhysRev.115.1522