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The specular reflectivity of x-rays at sufficiently small grazing angles is absorption-coefficient-dependent so that the EXAFS technique can be used to probe the surface. This method allows in situ measurements. Applications to the study of passive films on nickel and nickel-molybdenum alloy electrodes are presented. In both cases, the passive films is found to be composed of NiO entities probably ordered perpendicularly to the electrode. Molybdenum enrichment in the surface layer is confirmed by an increase of the Mo k edge signal.

The crystal structure of the metastable β-phase of toluene is determined from single crystal X-ray diffraction data using a Monte-Carlo method coupled to a constrained leastsquares refinement. At 105 K β-toluene is orthorhombic (space group Pbcn ; a = 13.85 A, b = 11.42 A, c = 7.39 A ; Z = 8). Relations between the packing of the molecules in this modification and in the normal crystalline α-phase are discussed.

The crystal and molecular structures of syndiotactic 2,4,6,8-tetraphenylnonane have been determined by direct methods and refinement from X-ray diffraction data. The unit cell is quadratic (space group I 4 1 /g) with, at room temperature, g  13.740, c  27.20 A, V = 5135.7 A, Z = 8 and contains one molecule in the asymmetric unit; the final weighted residual factor is r = 0.065 for 1541 observed reflexions. It is found that the aliphatic chain exhibits a gauche-gauche conformation in the middle of the chain.