Nature of Optical Transitions in Copper and Cu:Ni Alloys

The direct L_2^'→L₁ transition is very apparent in photoemission data from pure Cu; however, as might be expected, there is no evidence for this transition in 87% Cu-13% Ni alloys. In contrast, structure in ε₂ for hν>~2.1 eV for the alloy and pure Cu is qualitatively similar. These observations support the assignment of major structure in ε₂ of pure Cu to nondirect transitions from the d states and argue against the 5.0 eV peak being due principally to the L_2^'→L₁ transition.