The value of using Z r L a x-rays as a source tor the XPS study of AI-Si compounds is proved by their ability to generate strong Al and Si 1s and KLL Auger peaks and with sufficient resolution for peak energies to be determined accurately. A study of the resultant A1 and Si Auger parameters has been made for some 30 silicates and comparison with refractive index data allows the Auger parameters to be scaled directly with the polarization energy of the surrounding 0 ions. The 0 polarizability dominates the bulk polarizability in silicates and its magnitude is controlled by its site co-ordination number and the electronegativity of charge-balancing cations in the structure. Oxygen ions surrounding Si and tetrahedral Al sites have highly variable, but strongly interdependent, polarizabilities; however, the 0 polarizability is almost invariant around octahedral A1 sites. The correlation of relaxation energy in a silicate lattice with polarizability is finally compared with the London force interaction between molecules.

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Stainless steel and ceramic surfaces were subjected to repeated soiling and cleaning procedures, using a milk powder soil inoculated with Pseudomonas aeruginosa and Staphylococcus aureus, followed by spraying with water with or without 0.1% (vol/vol) nonionic detergent. Test surfaces were removed after 1, 5, 10, and 20 soiling-cleaning cycles and were analyzed for attached microorganisms (total viable count of bacteria removed by swabbing and percentage of coverage of cells plus soil stained with acridine orange). Surfaces were additionally examined using a range of analytical techniques: X-ray photoelectron spectroscopy (XPS), dynamic and imaging secondary ion mass spectroscopy (SIMS), and time-of-flight SIMS. Both microbiological and chemical analyses revealed an accumulation of material over the cycles to a maximum level. Surfaces were conditioned rapidly to saturation with organic material within one cycle (XPS), whereas fouling by microorganisms was less rapid (five cycles). Cleaning with detergent tended to retard the cumulative fouling process when compared with spray cleaning using water alone. The methods described provide a more realistic scenario for testing the cleanability of surfaces routinely found in food processing locations and for screening novel cleaning regimens and/or surface materials. The analytical techniques provide additional information on the kinetics of soiling, which complement the more familiar microbiological methods.

Monochromatization of AgLa X-rays is achieved by fitting an Ag anode to a conventional A l K a monochromator. Many new XPS lines are generated by this high energy source including the 1s and KLL Auger series from AI to CI. Chemical state determination by means of the Auger parameter for these elements is greatly assisted by the reduced X-ray linewidth after monochromatization. Three glass fibre samples with different surface pre-treatments were studied to show that chemical state information could be extracted from even these complex, rough and insulating surfaces by using this novel X-ray source.