NATURE OF OPTICAL TRANSITIONS IN COPPER AND CU - NI ALLOYS

The direct L2′→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 L2′→L1 transition. © 1969 The American Physical Society.