The orientation and the intramolecular relaxation due to adsorption of the chiral phenanthrene-derivative heptahelicene, C 30 H 18 , on Cu(lll) and Cu(332) smfaces have been investigated by means of angle-scanned full-hemispherical x-ray photoelectron diffraction. Although the C 1 s diffraction patterns of the adsorbed submonolayer coverage helicene films exhibit scattering anisotropies of less than two percent, a detailed analysis involving simple molecular mechanics calculations of the atomic coordinates, photoelectron diffraction single-scattering cluster calculations and an R-factor analysis permits the determination of the helicene molecular orientation. On Cu(lll), the molecules are found to bind to the substrate surface via their terminal phenanthrene group oriented parallel to the surface plane, while on Cu(332) the three terminal C-6 rings are oriented parallel to the (Ill) terrace plane. Six azimuthal molecular orientations are found to coexist on Cu(lll), on Cu(332), however, the step-molecule interaction leads to a unique azimuthal alignment of the heptahelicene molecules. The heptahelicene on Cu(332) system thus represents a chiral surface with single-phase orientational order.

Diethylaminosulfur trifluoride (DAST) is a very powerful reagent that allows the conversion of various alcohols to fluorine-containing products which can possess interesting biological activities. The fluorination process can occur in unison with a ring-expansion and/or ringcontraction.

Results from a spectromicroscopic study of the formation of TiSi2 in patterned structures are reported. An x-ray spectromicroscope was used to acquire spectra and images with photoabsorption signals using synchrotron radiation. A patterned TiSi2 sample with feature sizes ranging from 100 μm to 0.1 μm was studied. The silicidation reactions were carried out in ultrahigh vacuum using rapid thermal processing. Lateral variations in the local chemistry of the titanium silicide could be directly imaged and are attributed to the formation of the C54 phase in large areas and the C49 phase at feature edges and in narrow features.