A B S T R A C T: X-ray photoelectron diffraction data for three cleavage surfaces from a crystal of a Norwegian lepidolite containing 2.3% Rb and 3% Mn are reported and interpreted. Rubidium is shown to occupy anhydrous interlayer sites equivalent to those of potassium, and to be distributed uniformly throughout the crystals. Cleavage occurs in Mn rich regions in which the manganese(II) is located in octahedral sites essentially equivalent to those of lithium. The octahedral A1 sites can readily be distinguished from the Li,Mn sites and it is concluded that AI occupies predominantly M(2), cis sites while Li and Mn(lI) prefer M(1), trans sites. Photoelectron diffraction data also indicate that 40 + 5% of the AI is tetrahedrally coordinated, compared with a figure of ~34% deduced independently from a surface analysis.

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X-ray photoelectron diffraction data from single crystals of a biotite containing 1~o Ti show that although this element is located entirely in octahedral sites, the Ti sites are not precisely equivalent to those of Mg and Fe. Comparisons of Ti 2p X-ray photoelectron spectra from two biotites and from two titaniferous phlogopites ( ~0.3~0.5~ Ti) with those from Ti(II), Ti(IIl) and Ti(IV) oxides indicate that this element is present as Ti(llt) rather than Ti(IV) in all four micas.

The reaction of (100) surfaces of PbS crystals (natural galena) with reactive oxygen species generated by microwave discharge in NO has been compared with aerial oxidation in studies using angle-resolved X-ray and ultraviolet photoelectron spectroscopies. Reaction with the discharge products was much faster, facilitating the study of this process in a controlled environment. The final products of the two processes were similar.Initial attack by atomic oxygen at Pb sites led to the formation of oxide species with the liberation of free sulphur, most of which was lost from the surface. Some, however, remained trapped under an oxidized layer. Sulphate species were also formed, probably by direct attack on PbS. Surfaces of good crystallinity (assessed via their photoelectron diffraction patterns) and chemical purity could be regenerated from oxidized surfaces by 800 eV argon-ion bombardment followed by annealing at ca. 350 O C .Core-level binding energies (&) for bulk PbS, PbSO,, PbO, PbCO,, PbS,O, and 5Pb(OH), * Pb(NO,), were obtained via gold decoration and confirmed by reference to adventitious carbon. The Eb of the surface sulphate and oxide differed from those of the individual bulk lead salts, and they were inferred to coexist in an intimate mixture which probably also contained hydroxide. After the oxidized surfaces were heated to ca. 350 O C only the sulphate and some of the oxide remained.

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