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EVIDENCE FOR THE ITINERANT ELECTRON MODEL OF FERROMAGNETISM AND FOR SURFACE PHOTOEMISSION FROM ANGLE-RESOLVED PHOTOEMISSION STUDIES OF IRON

Description: Angle-resolved HeI photoemission spectra of Fe(001) are reported and interpreted within the framework of a direct transition model using Callaway's ferromagnetic band structure. The generally good agreement between predicted and experimental peak positions is taken to be strong support for the itinerant electron theory of ferromagnetism. Spectra taken with nearly grazing incidence p-polarized light emphasize the one-dimensional density of states peaks, supporting Kliewer's theoretical predictions of surface photoemission. The importance of electron refraction is noted, as is the value of interpolation calculations for interpreting ARP spectra.
Date: October 1, 1977
Creator: Kevan, S.D.; Wehner, P.S. & Shirley, D.A.
Partner: UNT Libraries Government Documents Department

TEMPERATURE INDEPENDENCE OF THE ANGLE-RESOLVED X-RAY PHOTOEMISSION SPECTRA OF GOLD AND PLATINUM VALENCE BANDS

Description: Angle-resolved valence-band x-ray photoemission spectra were taken along the [111] and [100] directions of gold single crystals and along the [100] direction of a platinum single crystal at room temperature (293K) and on a probe cooled nearly to liquid nitrogen temperature (77K). No change was detected on cooling the samples, in contrast to expectations based on a simple direct-transition model. A simple 'matrix-element' model appears to predict spectra well even at low temperatures, perhaps because the complexity of the high-energy final-state bands permits sampling effectively throughout the zone.
Date: September 1, 1977
Creator: Dabbousi, O. B.; Wehner, P.S. & Shirley, D.A.
Partner: UNT Libraries Government Documents Department

D-ORBITAL DIRECTED PHOTOEMISSION FROM MANGANESE FLUORIDE SINGLE CRYSTALS USING A1Kalpha RADIATION

Description: Angle-resolved photoemission energy distributions (PED's) were obtained from valence bands of MnF{sub 2} single crystals using AlK{alpha} radiation. A pronounced variation in the PED's was observed as the electron take-off angle was varied relative to the crystalline axes, for the (111) crystal face. The observed variation is attributed to the t{sub 2g} and e{sub g} symmetry properties of the manganese 3d initial state wave functions and is well described by an angle-dependent transition-matrix model. The results are in good agreement with the multi-configurational Hartree-Fock calculations of Viinikka and Bagus.
Date: September 1, 1977
Creator: Sherwood, P.M.A.; McFeely, F.R.; Kowalczyk, S.P. & Shirley, D.A.
Partner: UNT Libraries Government Documents Department

Photoemission studies of clean and adsorbate covered metal surfaces using synchrotron and uv radiation sources

Description: Photoemission energy distribution experiments on clean metal and adsorbate-covered surfaces were performed under ultrahigh vacuum conditions by using x-ray and ultraviolet photon sources in the laboratory as well as continuously-tunable, highly polarized synchrotron radiation obtainable at the Stanford Synchrotron Radiation Laboratory (SSRL). Studies focused on two general areas: cross-section modulation in the photoemission process was studied as a function of photon energy and orbital composition. Sharp decreases in intensity of the valence bands of several transition metals (i.e., Ag, Au, and Pt) are attributed to the radial nodes in the respective wave functions. Adsorbate photoemission studies of CO adsorbed on platinum single crystals have demonstrated a very high spectral sensitivity to the 4sigma and (1..pi.. + 5sigma) peaks of CO at photon energies of 150 eV. Angle-resolved photoemission allowed determination of the orientation of CO chemisorbed on a Pt (111) or Ni(111) surface. Prelinimary results at high photon energies (approximately 150 eV) indicated scattering from the substrate which could yield chemisorption site geometries.
Date: September 1, 1977
Creator: Apai, G.R. II
Partner: UNT Libraries Government Documents Department