L-shell soft-x-ray appearance-potential spectra of the 3d transition metals

We have obtained L-Shell appearance-potential spectra for clean surfaces of the $3d$ transition metals: Sc, Ti, V, Cr, Mn, Fe, Co, and Ni. Spin-orbit splittings determined from these spectra are in excellent agreement with tabulated x-ray values. In all cases, however, the absolute binding energies are lower than the tabulated values, presumably as a result of the reduced coordination for surface atoms. The $\frac{L_3}{L_2}$ intensity ratios show a systematic variation with Z, approaching the expected statistical weighting of 2 only for a nearly empty (Sc) or nearly filled (Co and Ni) $3d$ band. It is less than 2 for all intermediate Z's with a minimum value of approximately 1 at Cr. The L₃, L₂ peak widths decrease with Z corresponding to the filling of the $3d$ band. The L₁ width, which is determined primarily by Auger lifetime broadening rather than the density of conduction-band states, exhibits a systematic decrease for Z>24 in contrast to theoretical predictions.