The photoelectron spectra of some 40 transition metal compounds have been measured using AlKα(1487 eV) and MgKα(1254 eV) x-rays. The compounds included both simple salts (halides and chalcogenides) and hexacoordinated complexes (cyano- and fluoro-) of Cr(III), Mn(II, III), Fe(II, III), and Co(III). From these data we have determined the chemical shifts of the core electrons and related these results to a calculated charge based on Pauling's electronegativities. In addition, multiplet splitting has been obtained for photoionization in the 3s shell and is discussed in terms of the exchange interaction between the partially filled 3s and 3d orbitals. To help in this explanation, calculations were made using both (1) Hartree-Fock solutions of the wavefunctions for free ions and (2) a qualitative evaluation of the behavior of the exchange integral. The value of using x-ray photoelectron spectroscopy for studying chemical bonding for transition metal compounds is amply illustrated.

Publication costs assisted by the University of Georgia X-ray photoelectron spectroscopy (ESCA) has been used to study the surface reactions of a commercial cobalt-molybdenum-alumina catalyst. Reduction of the catalyst in hydrogen produced a mixture of molybdenum oxidation states: Mo(VI), Mo(V), and Mo(IV). The relative amount of molybdenum in each state was determined as a function of reduction time and temperature. Exposure of fired catalysts to thiophene in an inert atmosphere showed that only thiophene adsorption occurred. In contrast fired, prereduced catalysts showed both thiophene adsorption and desulfurization capability in an inert atmosphere. The molybdenum of the catalyst was effectively sulfided in either thiophene/H2 or H2S/H2. However, prereduced catalysts sulfided to a lesser extent than catalysts that had only been fired. In no case was complete sulfiding of the molybdenum observed. The cobalt of the catalyst showed little change on treatment with either hydrogen or thiophene/H2. This was in contrast to application of H2S/H2 which sulfided the cobalt of the catalyst more rapidly than the cobalt in cobalt aluminate.

Trade names and company names are included as a matter of convenience to the reader, and such inclusion does not constitute any preferential endorsement by the U. S. Department of Agriculture of products named over similar products available on the market. Contribution of the Agricultural Research Service, USDA, in cooperation with Colorado State University Experiment Station, Scientific Journal Series No. 1787. This research was supported in part by the Environmental Protection Agency.

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