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8th international conference on electronic spectroscopy and structure

Description: Gathering from 33 countries around the world, 408 registrants and a number of local drop-in participants descended on the Clark Kerr Campus of the University of California, Berkeley, from Monday, August 7 through Saturday, August 12, 2000 for the Eighth International Conference on Electronic Structure and Spectroscopy (ICESS8). At the conference, participants benefited from an extensive scientific program comprising more than 100 oral presentations (plenary lectures and invited and contributed talks) and 330 poster presentations, as well as ample time for socializing and a tour of the Advanced Light Source (ALS) at the nearby Lawrence Berkeley National Laboratory.
Date: October 16, 2000
Creator: Robinson, Art
Partner: UNT Libraries Government Documents Department

Electron spectroscopy studies of argon K-shell excitation and vacancy cascades

Description: Electron spectroscopy combined with tunable synchrotron radiation has been used for studies of Ar K-shell excitation and vacancy decay processes. In addition, electrons and fluorescent X-rays have been recorded in coincidence to select subsets of the ejected electron spectra. Examples are presented for Ar 1s photoelectrons and KLL and LMM Auger spectra.
Date: February 1, 1995
Creator: Southworth, S. H.; MacDonald, M. A.; LeBrun, T.; Azuma, Y. & Cooper, J. W.
Partner: UNT Libraries Government Documents Department

Manifestations of sequential electron transfer

Description: An essential feature of efficient photo-initiated charge separation is sequential electron transfer. Charge separation is initiated by photoexcitation of an electron donor followed by rapid electron transfer steps from the excited donor through a series of electron acceptors, so that, after one or two successive steps, charge separation is stabilized by the physical separation between the oxidized donor and reduced acceptor. The prime example of this process is the sequential electron transfer that takes place in the purple photosynthetic bacterial reaction center, resulting in the charge separation between P{sup +} and Q{sub A}{sup -} across a biological membrane. We have developed magnetic resonance tools to monitor sequential electron transfer. We are applying these techniques to study charge separation in natural photo-synthetic systems in order to gain insights into the features of the reaction center proteins that promote efficient charge separation. As we establish what some of these factors are, we are beginning to design artificial photosynthetic systems that undergo photoinduced sequential electron transfer steps.
Date: May 1, 1996
Creator: Thurnauer, M.C. & Tang, J.
Partner: UNT Libraries Government Documents Department

EPR dosimetry teeth in past and future accidents: A prospective look at a retrospective method

Description: Accurate assessments of doses received by individuals exposed to radiation from nuclear accidents and incidents such as those at Hiroshima and Nagasaki, the Nevada test site, Cheliabinsk and Mayak are required for epidemiological studies seeking to establish relationships between radiation dose and health effects. One method of retrospective dosimetry which allows for measurement of cumulative gamma ray doses received by exposed individuals is electron paramagnetic resonance spectroscopy (EPR) of tooth enamel. Tooth enamel stores and retains, indefinitely, information on absorbed radiation dose. And teeth are available in every population as a result of dental extraction for medical reasons including periodontal disease and impacted wisdom teeth. In the case of children, deciduous teeth, which are shed between the ages of 7 and 13, can be a very important dosimetric source if documented collection is implemented shortly following an accident.
Date: March 1, 1997
Creator: Haskell, E.; Kenner, G.; Hayes, R.; Chumak, V. & Shalom, S.
Partner: UNT Libraries Government Documents Department

Resonant Auger studies of metallic systems

Description: Results of resonant Auger spectroscopy experiments are presented for Cu, Co, and oxidized Al. Sub-lifetime narrowing of Auger spectra and generation of sub-lifetime narrowed absorption spectra constructed from Auger yield measurements, were observed. Resonant Auger yields are used to identify three valence states of oxidized Al. Partial absorption yield spectra were derived giving detailed electronic information and thickness information for the various chemical states of the bulk metal, the passivating aluminum oxide layer, and the metal-oxide interface region. In addition, the total absorption yield spectrum for the oxidized Al sample was constructed from the partial yield data, supporting the consistency of the authors method.
Date: October 21, 1999
Creator: Coulthard, I.; Antel, W. J., Jr.; Frigo, S. P.; Freeland, J. W.; Moore, J.; Calaway, W. S. et al.
Partner: UNT Libraries Government Documents Department

Sodium Depletion on Glass Surfaces During Auger Analysis

Description: The kinetics of the depletion of sodium on glass surfaces during Auger Electron Spectroscopic analysis is investigated. The decay process is mathematically represented as a sum of two single decaying exponential functions. This behavior may be described by a mechanism that accounts for the neutralization of sodium ions by the electron beam. Sodium ions and neutral sodium atoms are depleted by several known processes.
Date: April 22, 1981
Creator: Whitkop, P.G.
Partner: UNT Libraries Government Documents Department

[Studies of autoionizing states relevant to dielectronic recombination. Final report]

Description: Laser spectroscopy experiments on autoionizing states of alkaline earth atoms allow the inverse process, dielectronic recombination, to be studied in great detail under controlled and variable conditions. The research is also relevant to problems in physical chemistry involving excited molecules, and it has helped to clarify the physical processes of zero kinetic energy electron spectroscopy and coherent control.
Date: October 15, 1999
Creator: Gallagher, Thomas P.
Partner: UNT Libraries Government Documents Department

Irradiation-assisted stress corrosion cracking behavior of austenitic stainless steels applicable to LWR core internals.

Description: This report summarizes work performed at Argonne National Laboratory on irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels that were irradiated in the Halden reactor in simulation of irradiation-induced degradation of boiling water reactor (BWR) core internal components. Slow-strain-rate tensile tests in BWR-like oxidizing water were conducted on 27 austenitic stainless steel alloys that were irradiated at 288 C in helium to 0.4, 1.3, and 3.0 dpa. Fractographic analysis was conducted to determine the fracture surface morphology. Microchemical analysis by Auger electron spectroscopy was performed on BWR neutron absorber tubes to characterize grain-boundary segregation of important elements under BWR conditions. At 0.4 and 1.4 dpa, transgranular fracture was mixed with intergranular fracture. At 3 dpa, transgranular cracking was negligible, and fracture surface was either dominantly intergranular, as in field-cracked core internals, or dominantly ductile or mixed. This behavior indicates that percent intergranular stress corrosion cracking determined at {approx}3 dpa is a good measure of IASCC susceptibility. At {approx}1.4 dpa, a beneficial effect of a high concentration of Si (0.8-1.5 wt.%) was observed. At {approx}3 dpa, however, such effect was obscured by a deleterious effect of S. Excellent resistance to IASCC was observed up to {approx}3 dpa for eight heats of Types 304, 316, and 348 steel that contain very low concentrations of S. Susceptibility of Types 304 and 316 steels that contain >0.003 wt.% S increased drastically. This indicates that a sulfur related critical phenomenon plays an important role in IASCC. A sulfur content of <0.002 wt.% is the primary material factor necessary to ensure good resistance to IASCC. However, for Types 304L and 316L steel and their high-purity counterparts, a sulfur content of <0.002 wt.% alone is not a sufficient condition to ensure good resistance to IASCC. This is in distinct contrast to the behavior of their high-C ...
Date: January 31, 2006
Creator: Chung, H. M.; Shack, W. J. & Technology, Energy
Partner: UNT Libraries Government Documents Department

In situ photoelectron spectroscopy study of water adsorption on model biomaterial surfaces

Description: Using in situ photoelectron spectroscopy at near ambient conditions, we compare the interaction of water with four different model biomaterial surfaces: self-assembled thiol monolayers on Au(111) that are functionalized with methyl, hydroxyl, and carboxyl groups, and phosphatidylcholine (POPC) lipid films on Silicon. We show that the interaction of water with biomaterial surfaces is mediated by polar functional groups that interact strongly with water molecules through hydrogen bonding, resulting in adsorption of 0.2-0.3 ML water on the polar thiol films in 700 mTorr water pressure and resulting in characteristic N1s and P2p shifts for the POPC films. Provided that beam damage is carefully controlled, in situ electron spectroscopy can give valuable information about water adsorption which is not accessible under ultra-high vacuum conditions.
Date: July 10, 2007
Creator: Salmeron, Miquel; Ketteler, Guido; Ashby, Paul; Mun, B.S.; Ratera, I.; Bluhm, Hendrik et al.
Partner: UNT Libraries Government Documents Department

Measurements and characterization - Surface analysis

Description: This brochure presents the capabilities that the Measurements and Characterization Division has in Surface Analysis, in which a variety of spectrometry and spectroscopy techniques are used to determine the chemical, elemental, and molecular composition of material surfaces and interfaces.
Date: March 16, 2000
Creator: Cook, G.
Partner: UNT Libraries Government Documents Department

Initial stages of oxidation of metals and alloys. Progress report, May 1, 1980-April 30, 1981

Description: Studies of the oxidation kinetics of Ni-Fe alloys and of Be have been carried out over the past year. The majority of the alloy results are for the (100) surface of Fe/sub 40/Ni/sub 60/. Investigation of the clean surface over the temperature range up to approx. 900/sup 0/C indicated only a slight enrichment in Fe relative to Ni compared to the bulk average composition. Under oxidizing conditions the situation is quite different; marked segregation of Fe occurs with the formation of iron oxide overlayers. The kinetics of this process have been studied using Auger spectroscopy and structural features of the overlayer observed by LEED. The LEED observations indicate the initial formation of (lll) oriented FeO on Fe/sub 40/Ni/sub 60/ (100); at greater oxygen exposures a new oxide structure, probably Fe/sub 3/O/sub 4/, develops with its (lll) plane parallel to the (100) substrate. With Be the room temperature oxidation has been investigated over the pressure range 10/sup -7/ to 10/sup -9/ mm Hg. Auger lineshape studies indicate that most of the Be spectrum can be accounted for by contributions from clean Be and BeO. Data on the kinetics at 300 K have been obtained. A research ellipsometer with rotating analyzer has been installed and interfaced to a computer system.
Date: April 1, 1981
Creator: Blakely, J. M.
Partner: UNT Libraries Government Documents Department

Auger study of surface carbon and oxygen on thorium following ion bombardment

Description: The composition of a thorium metal surface has been monitored using Auger electron spectroscopy following Ar/sup +/ bombardment at different temperatures. After extended Ar/sup +/ bombardment, enough contaminated overlayers were removed to expose a surface region containing only thorium, bulk impurities, and imbedded argon. The main impurities, carbon and oxygen, differed in their behavior when the sample was annealed following bombardment. The amount of surface carbon either increased or remained constant during annealing depending upon the temperature of the sample during bombardment. The amount of surface oxygen decreased rapidly when the sample was heated above 500/sup 0/C regardless of the sample temperature during bombardment. These experiments indicate that preparation of clean, annealed thorium surfaces requires ion bombardment at temperatures > or = 400/sup 0/C.
Date: November 17, 1977
Creator: Bastasz, R. & Colmenares, C.
Partner: UNT Libraries Government Documents Department

Laboratory studies of spectroscopic markers for the characterization of surface erosion by plasmas

Description: The erosion rates in portions of fusion plasma devices like the ITER tokamak are sufficiently high that nearly real-time information on cumulative removal is needed for control and machine safety. We are developing a digitally--encoded scheme to indicate the depth of erosion at numerous poloidal and toroidal locations around ITER. The scheme uses materials embedded in the walls and divertors, which, when uncovered, present remotely detectable signals. This paper reports laboratory experiments on prototype markers consisting of combinations of up to 5 elements (Au,Pd,Ag,In,Ga) along with Au,Pt, and Ta pure metals. The markers were bonded to 4-D carbon-carbon composite of the type proposed for use in the ITER first wall, and placed in the lower-hybrid-driven plasma of the atomic beam facility at PPL. The paper describes this device Light emission was characterized using a 1 meter Czerny-Turner vacuum ultraviolet monochromator. The samples were characterized both before and after plasma exposure by Auger spectroscopy. We report the time-dependent behavior of the spectra of the visible and ultraviolet light emitted by the plasma when the markers are uncovered by the erosion showing emission lines of the marker elements which are easily distinguished from the background plasma lines. The dependence of the light intensity on bias voltage is compared to the known sputtering yields of the elements. The optical detection method allows exploration of the threshold dependence of these multi-element targets. An exponential dependence of yield above threshold was observed for all of the elements studied.
Date: January 1, 1992
Creator: Manos, D.M.; Bennett, T.; Herzer, M. & Schwarzmann, J.
Partner: UNT Libraries Government Documents Department

Surface electronic structure of GaAs(110) studied by Auger photoelectron coincidence spectroscopy

Description: We have used Auger photoelectron coincidence spectroscopy to study the M{sub 4,5}VV Auger spectra of GaAs(110). Using this technique, the Ga and As spectra can be separated and studied independently. The lineshape of the As-M{sub 4,5}VV measured in coincidence with the As 3d photoemission line differs significantly from the conventional Auger spectrum. We attribute this to the surface electronic properties of the system. In addition, we have found that the ss-component of the As spectrum is more intense than expected based on calculations using atomic matrix elements. The Ga-M{sub 4,5}VV spectrum, of which only the pp-component is observed, agrees well with that expected from an independent electron model. A first principles electronic structure calculation of a 5-layer GaAs(110) slab has been performed to aid in the interpretation of the Auger spectra.
Date: January 1, 1990
Creator: Bartynski, R.A.; Garrison, K. (Rutgers--the State Univ., Piscataway, NJ (United States)); Jensen, E. (Brandeis Univ., Waltham, MA (United States). Dept. of Physics); Hulbert, S.L. & Weinert, M. (Brookhaven National Lab., Upton, NY (United States))
Partner: UNT Libraries Government Documents Department

Solution softening in molybdenum-rhenium alloys

Description: This study has clearly demonstrated the solution softening phenomenon in Mo-Re alloys that contain 5.8 to 8.2 at. % Re. The intrinsic nature of the phenomenon tends to be supported by this work; however, the addition of rhenium to molybdenum appears to cause a redistribution of interstitials that affects the fracture behavior in worked alloys. Much more fundamental research is needed to clearly establish the mechanisms that cause this phenomenon. The fabrication of these alloys seems to be no more difficult than any molybdenum alloys produced commercially today. Even the control of rhenium content in the maximum solution softening range does not appear to be difficult.
Date: January 1, 1984
Creator: Lundberg, L.B.; Ohriner, E.K.; Tuominen, S.M. & Whelan, E.P.
Partner: UNT Libraries Government Documents Department

Silicon-based coatings on niobium metal

Description: Silicon coatings on niobium substrates were subjected to thermal, ion beam and laser mixing, and the effectiveness of the different methods for the synthesis of graded interfaces was compared. The resulting metal/silicon interfaces were characterized by x-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES) and the Rutherford backscattering (RBS). 6 refs., 4 figs.
Date: January 1, 1989
Creator: Stupik, P.D.; Jervis, T.R.; Nastasi, M.; Donovan, M.M.; Barron, A.R. (Harvard Univ., Cambridge, MA (USA). Dept. of Chemistry; Los Alamos National Lab., NM (USA) et al.
Partner: UNT Libraries Government Documents Department

Temperature dependent effects during Ag deposition on Cu(110)

Description: The composition, structure, and morphology of ultrathin films grown by Ag deposition on Cu(110) were monitored as a function of temperature using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and medium energy ion scattering (MEIS). Aligned backscattering measurements with 150 keV He ions indicate that the Ag resides on top of the Cu and there is no significant surface compound formation. Measurements with LEED show that the Ag is initially confined to the substrate troughs. Further deposition forces the Ag out of the troughs and results in a split c(2 {times} 4) LEED pattern, which is characteristic of a distorted Ag(111) monolayer template. As verified by both AES and MEIS measurements, postmonolayer deposition of Ag on Cu(110) at 300K leads to a pronounced 3-dimensional clustering. Ion blocking analysis of the Ag clusters show that the crystallites have a (110)-like growth orientation, implying that the Ag monolayer template undergoes a rearrangement. These data are confirmed by low temperature LEED results in the absence of clusters, which indicate that Ag multilayers grow from a Ag--Cu interface where the Ag is captured in the troughs. Changes observed in the film structure and morphology are consistent with a film growth mechanism that is driven by overlayer strain response to the substrate corrugation. 16 refs., 4 figs.
Date: January 1, 1989
Creator: Taylor, T.N.; Muenchausen, R.E.; Hoffbauer, M.A.; Denier van der Gon, A.W.; van der Veen, J.F. (Los Alamos National Lab., NM (USA) & FOM-Instituut voor Atoom-en Molecuulfysica, Amsterdam (Netherlands))
Partner: UNT Libraries Government Documents Department

Quasi-static intergranular cracking in a Cu-Sn alloy: An analog of stress relief cracking of steels

Description: Intergranular cracking in a laboratory-made Cu-8wt%Sn alloy at 265 to 300{degree}C in vacuum was studied in order to explore the hypothesis that this could serve as an analog to the brittle mode of stress-relief cracking in steels and to test the mechanism proposed earlier to explain that phenomenon. This mechanism involves the stress-induced intergranular penetration along grain boundaries of a surface-adsorbed embrittling element. Sulfur is the active element in this regard in steels, and tin was envisioned as playing the same role in Cu-Sn alloys. Auger spectroscopy was used to confirm earlier reports of the surface activity of tin and to determine the segregation kinetics in the present polycrystals; no other elements were found to segregate to surfaces to any significant degree in the present alloy. Crack growth measurements showed that intergranular cracking occurs in an intermittent manner at an average rate on the order of 0.1 {mu}m/sec over a range of crack length. Crack initiation was found to be remarkably sensitive to the stress intensity, implying the existence of a threshold. The fracture appearance in the regions of slow crack growth was similar to that observed in steels undergoing stress-relief cracking at 500--600{degree}C. It was concluded that the quasi-static intergranular cracking in the steels and in the Cu-Sn alloy represent two aspects of the same generic phenomenon and that the proposed mechanism of stress-induced intergranular impurity penetration is valid. It is believed that liquid-and solid-metal embrittlement are closely related to the type of intergranular cracking described here.
Date: January 1, 1991
Creator: Barrera, E.V.; Menyhard, M.; Bika, D.; Rothman, B. & McMahon, C.J. Jr.
Partner: UNT Libraries Government Documents Department

Surface analysis of TFTR vacuum vessel samples subjected to the post-weld heat treatment

Description: To ensure the dimensional stability of the Tokamak Fusion Test Reactor (TFTR) vacuum vessel, it is necessary to perform a post-weld heat treatment (PWHT). This process consists of heating the vessel segments to approx. 450/sup 0/C for 1.5 h. The large size of the segments precludes a vacuum bake previous to installation. Effects of the PWHT on the vacuum vessel surface were studied using small samples of vessel material which were subjected to a variety of PWHT procedures, including inert gas purges and different oven designs. Changes in topography and near-surface chemistry were investigated with SEM and sputter-Auger electron spectroscopy. These samples were compared with the surface properties of non-baked UHV-quality stainless steel. The primary difference noted between the PWHT samples and the non-baked control was the thickness of the passivation oxide layer. The thickness of this mixed oxide (FeO/Cr/sub 2/O/sub 3//NiO) on the control sample was less than or equal to 100 A. The thickness of the oxide layer on the heat-treated samples ranged between 230 to 350 A, depending on the method of the PWHT. The effect of hydrogen glow discharge cleaning on these thicker oxide layers, and the consequences of such heat treatment procedure relative to oxygen impurity production in fusion devices are discussed.
Date: November 1, 1980
Creator: Moore, R. L.; Cohen, S. A.; Cecchi, J. L. & Dylla, H. F.
Partner: UNT Libraries Government Documents Department