Occupied Band Structure of Cu: Soft-X-Ray Spectrum and Comparison with Other Deep-Band-Probe Studies

We report a new measurement of the soft-x-ray $M_{2,3}$ emission spectrum of Cu, using improved experimental techniques. Previously unreported fine structure was observed in the spectrum. Although exact correction for satellite and subband overlap and self-absorption effects is not yet possible, careful consideration has been given to them, with the result that the $M_3$ band profile can be resolved from the accompanying structure in a plausible way. Its features can be taken with reasonable confidence to be characteristic of the true $M_3$ profile. Comparison is made with the complementary $L_3$ soft-x-ray profile, with band-theoretical estimates of both experimental x-ray profiles, and with the results of ultraviolet-photoemission, x-ray-photoemission, and ion-neutralization measurements. These comparisons favor a single-particle description of the occupied bands of Cu.