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Theoretical predictions of a new phenomenon arising in photoelectron emission from oriented molecules by circularly polarized light have been experimentally verified for CO. For a special geometry photoelectron-intensity differences occur upon reversal of photon helicity. The measured asymmetries (up to 80%) show good agreement with an ab initio calculation at photon energies between 20 and 40 eV. Theoretically, the new manifestation of circular dichroism is already obtained in the pure electric dipole approximation without inclusion of spin-orbit interaction.PACS numbers: 33.60. Cv, 33.55.Ad, 33.80.Eh In recent years several theoretical investigations have predicted circular dichroism (CD) in photoemission, a phenomenon leading to different photoelectron intensities when the ionizing light is either left-or rightcircularly polarized. Regarding its outward appearance, this effect shows complete analogy to the "classical" CD in photoabsorption, 6 well known for optically active molecules without a plane or center of symmetry. Classical CD is described by an interference of electric and magnetic dipole transitions. Consequently, the measured asymmetries are relatively weak. 7 For obvious reasons, CD with chiral molecules should be visible in photoemission as well. Ritchie x first pointed out that nonchiral molecules also might show a circular dichroism in the angular distribution (CDAD) of photoelectrons if they are fixed in space (we will call this spatially oriented). Cherepkov 2 found that for all fixed molecules CDAD occurs in the electric dipole approximation. Proceeding from this important result he predicted that CDAD asymmetries are of the same order of magnitude as the differential cross section itself and hence should be easily observable in a photoemission experiment.A numerical model calculation of CDAD in photoemission from the 4

Mass-filtered 3d transition metal nanoparticles have been produced by means of an ultrahigh vacuum compatible arc cluster ion source. High resolution transmission electron microscopy images of individual Fe, Co, and FeCo alloy particles with diameters of about 12 nm reveal the crystalline structure of the nanoparticles. X-ray absorption spectroscopy confirms the purity of the particles after in situ deposition. Analysis of the x-ray magnetic circular dichroism reveals bulklike total magnetic moments in all cases and strongly enhanced orbital moments for the iron nanoparticles. Furthermore, the data hint at a chemically ordered alloy in the case of FeCo particles.

The local density of states (LDOS) of the adsorbate induced two-dimensional electron system (2DES) on n-InAs(110) is studied by low-temperature scan-

We investigated the growth of Co submonolayers on bcc W͑110͒ by scanning tunneling microscopy. Due to the strong Co-W bonding, monolayers of Co grow in equilibrium pseudomorphically on W͑110͒ until the monolayer is almost completed. When excess atoms are deposited atop the pseudomorphic monolayer, it transforms to a close-packed ͑cp͒ monolayer with misfit dislocation lines parallel to ͓11 0͔ ͑Nishiyama-Wassermann orientation͒. The structure of the cp monolayer, as concluded from atomically resolved STM images, deviates from the rigid hard-sphere model of a cp ͑111͒ layer. Details of the structure are compared to a structure model previously proposed by van der Merwe et al. based on the embedded atom model ͑EAM͒.