Tungsten carbide has been shown to be an effective catalyst for a number of reactions that are readily catalyzed by platinum, but not at all by tungsten, and it was speculated that this behavior is due to changes in the electron distribution when carbon is added to tungsten. A test of this hypothesis, made by measuring the valence band x-ray photoelectron spectrum of tungsten carbide and comparing it with the spectra of tungsten and platinum, shows that, near the Fermi level, the electronic density of states of tungsten carbide more nearly resembles that of platinum than that of tungsten.

Soft-x-ray studies have been made on paramagnetic Ni and interpreted in terms of the single-particle density of states. In particular, the Af 2 ,3 emission spectrum has been investigated, using improved experimental techniques. Measurements were made at 960°C, at an average pressure of 5X10~8 Torr, using an oxide-free surface. Fine structure was observed in the spectrum. Although first-principles correction of self-absorption effects and satellite and subband overlap is not yet possible, careful consideration is given them, with the result that the Ms band can be resolved from the accompanying structure in a plausible way. Most of its features can be taken with reasonable confidence to be characteristic of the true M% emission band. Comparison is made with earlier soft-x-ray results, with band calculations for paramagnetic Ni, and with ion neutralization and photoemission measurements on ferromagnetic Ni. Systematic variations in transition matrix elements and lifetime broadening appear important when relating any experiment with theory, and an aspect of each of these problems has been considered quantitatively. The variation obtained is more severe for the photoemission than for the soft-x-ray analysis. The ion-neutralization and soft-x-ray results appear closer to the single-particle density of states.

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Measurements of the soft-x-ray M, , emission spectra of face-centered Fe and Co, and body-centered Fe, Cr, and V are reported and M3 single-hole excitation profiles are estimated. 3d bandwidths inferred from these results and earlier data on Cu and Ni are compared with band-theory predictions. As has been seen previously with x-ray and ultraviolet photoemission, the experimental Ni bandwidth is markedly narrower than theory predicts; there is a suggestion that the bandwidth of Cu is somewhat broader; theory and the present results are in fair agreement for the other metals. Fine structure is seen in the spectra; correlations are noted in the w+'a~structure of metals of common crystal structure; and structural correlations with x-ray and ultraviolet photoemission data are seen as well.

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