Virtual-Bound-State—Induced Optical Absorptivity in CuNi Alloys

The optical absorptivity of dilute CuNi alloys at 4^∘{}K has been measured for photon energies between 0.1 and 3 eV and Ni concentrations between 0.5 and 4 at.%. The data are interpreted in terms of the Anderson model of magnetic impurities. A virtual bound state is found 0.75±{}0.02 eV below the Fermi energy with a half-width of 0.27±{}0.02 eV. The extra absorptivity of the alloy is found to arise predominantly from the scattering of the host conduction electrons in the presence of the virtual bound state.