Surface composition and structure of palladium ultra-thin films deposited on Ni(1 1 1)

Ultra-thin palladium films deposited on the Ni(1 1 1) surface were characterized by X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and X-ray photoelectron diffraction (XPD). For low coverage, LEED shows a (1 × 1) pattern similar to that of the substrate. For intermediate coverage, the LEED pattern displays extra spots around the main (1 × 1) spots, resembling a Moiré coincidence pattern, probably associated with the formation of Pd bi-dimensional islands oriented in different directions on the Ni(1 1 1) surface. The results obtained by XPS and XPD corroborate this finding. The LEED pattern displays this structure up to 500 °C. Annealing at 650 °C brings back the (1 × 1) pattern, which is associated with a Pd island coalescence and alloy formation by Pd diffusion in the first atomic layers of the Ni(1 1 1). In this paper we present a detailed study of this surface structure via a comparison between XPD experiment and theory.     

A numerical approach to proving projectivity

Summary We present a nonconstructive method which uses intersection numbers and linear space theory for proving the existence of projective embeddings of suitable algebraic schemes, and we apply it to establish Chevalley's conjecture that a complete nonsingular variety such that any finite number of points is contained in an open affine subset is projective. In memory of Guido Castelnuovo in the recurrence of the first centenary of his birth.     

On directly measuring relative Fermi energies of noble metals and their alloys

We present the first evidence of direct measurement of relative Fermi energies in alloys and between pure metals. From applying the “atomic” concept of core hole final state screening, the Auger energy shift of noble metal A equals E_F^A?E_F(x). High resolution Auger shifts in P_1?x^tCu_x,Au_xCu_1?x and Au_xAg_1?x demonstrate experimental verification of this simple relation. We find E_F^CuE_F^Au ? ? 0.2 eV, and E_F^Pt ? E_F^Cu and E_F^Ag ? E_F^Au.     

Autoduality of the Compactified Jacobian

The following autoduality theorem is proved for an integralprojective curve C in any characteristic. Given an invertiblesheaf L of degree 1, form the corresponding Abel map A_L:C, which maps C into its compactifiedJacobian, and form its pullback map , which carries the connected component of 0 in the Picard schemeback to the Jacobian. If C has, at worst, points of multiplicity2, then is an isomorphism, and forming it commutes with specializing C. Much of the work in the paper is valid, more generally, fora family of curves with, at worst, points of embedding dimension2. In this case, the determinant of cohomology is used to constructa right inverse to . Then a scheme-theoretic version of the theorem of the cube is proved,generalizing Mumford's, and it is used to prove that is independent of the choice of L.Finally, the autoduality theorem is proved. The presentationscheme is used to achieve an induction on the difference betweenthe arithmetic and geometric genera; here, special propertiesof points of multiplicity 2 are used.     

Structure of Cu(100) from low energy electron diffraction: I. Specular beam

An extensive series of LEED measurements were made for clean Cu(100) for specular beams in a manner consistent with current data-averaging techniques. The results pertaining to surface geometrical structures were determined by analyzing the elastic intensity profiles with both current LEED data averaging techniques and calculations based upon the inelastic collision model. The resulting geometrical structures are compared with one another, yielding a systematic critique of the various LEED averaging techniques based upon a large amount of data. The surface layer spacing for clean Cu(100) was found to be $\text{1.8 ± 0.01}\text{A}\text{?}$.     

The canonical model of a singular curve

We give refined statements and modern proofs of Rosenlicht’s results about the canonical model C′ of an arbitrary complete integral curve C. Notably, we prove that C and C′ are birationally equivalent if and only if C is nonhyperelliptic, and that, if C is nonhyperelliptic, then C′ is equal to the blowup of C with respect to the canonical sheaf ω. We also prove some new results: we determine just when C′ is rational normal, arithmetically normal, projectively normal, and linearly normal.