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Methods of Opacity Calculations

Description: "Methods for calculating the opacity of materials at high temperatures are discussed in this report. Minor improvements are outlined for the treatment of continuous absorption processes, and a small error usually made in treating the scattering process is corrected. In contrast to all previous calculations of opacity, the effect of line absorption is carefully examined, for it may well be the dominant process under certain conditions of temperature and density. Detailed methods for calculating the line absorption contribution are, therefore, developed. To illustrate the principles involved, the opacity of pure iron at a temperature of 1000 volts and normal density is worked out in detail" (p. ii).
Date: 1949
Creator: Mayer, Harris
Partner: UNT Libraries Government Documents Department

Activation Cross Sections by Boron Absorption

Description: The following report studies the neutron activation cross-sections with the insertion of boron absorbers in the energy region 10 to 20,000 ev and the elements within the range.
Date: 1948
Creator: Dancoff, Sidney M., 1913-1951; Kubitschek, H.; Lichtenberger, H. V.; Monk, G. D. & Nobles, R. G.
Partner: UNT Libraries Government Documents Department

A Variable Speed Fan Dynamometer

Description: Fan brakes used as absorption dynamometers in testing internal combustion engines have the disadvantage that a given fan will run only at one speed when the engine is delivering full power. In order to be able to vary the speed at which a given power will be absorbed, English manufacturers have for some time been using a cylindrical housing around the fan with one or two variable openings in the periphery. Here, results are given of tests conducted to determine how great a range of speed can be obtained from such a device.
Date: December 1920
Creator: Wood, Karl D.
Partner: UNT Libraries Government Documents Department

The Development and Application of Capillary Absorption Cells

Description: Abstract: "Various types of capillary absorption cells have been constructed from a variety of materials. These cells, having volumes as low as 160 microliters, have been used to increase the sensitivity of several colorimetrics methods as much as 1000 fold without appreciable loss of accuracy. Small volumes of solution must be used in order to concentrate the colored material present."
Date: 1951
Creator: Rosenfels, R. S.; Kirk, P. L.; Kitson, R. E.; Patton, R. L. & Curtis, R. E.
Partner: UNT Libraries Government Documents Department

Nonlinear Optical Absorption and Refraction Study of Metallophthalocyanine Dyes

Description: This dissertation deals with the characterization of the nonlinear absorption and refraction of two representative metallophthalocyanine dyes: chloro aluminum phthalocyanine dissolved in methanol, referred to as CAP, and a silicon naphthalocyanine derivative dissolved in toluene, referred to as SiNc. Using the Z-scan technique, the experiments are performed on both the picosecond and nanosecond timescales at a wavelength of 0.532 μm.
Date: December 1992
Creator: Wei, Tai-Huei
Partner: UNT Libraries


Description: Sensitive (0.15 ppm) and unambiguous detection of carbon monoxide is reported and a comparison of acoustically resonant and nonresonant detectors is given. The pressure dependence of the optoacoustic signal is discussed in the context of atmospheric absorption.
Date: October 1, 1977
Creator: Gerlach, R. & Amer, N.M.
Partner: UNT Libraries Government Documents Department

Symmetry, Optical Properties and Thermodynamics of Neptunium(V) Complexes

Description: Recent results on the optical absorption and symmetry of the Np(V) complexes with dicarboxylate and diamide ligands are reviewed. The importance of recognizing the 'silent' feature of centrosymmetric Np(V) species in analyzing the absorption spectra and calculating the thermodynamic constants of Np(V) complexes is emphasized.
Date: December 21, 2009
Creator: Rao, Linfeng & Tian, Guoxin
Partner: UNT Libraries Government Documents Department

Effects of backlight structure on absorption experiments

Description: The impact of spectral details in the backlight of absorption spectroscopy experiments is considered. It is shown that experimentally unresolved structure in the backlight spectrum can introduce significant errors in the inferred transmission. Furthermore, it is shown that a valuable experimental procedure previously used to test the accuracy of the data fails to reveal these errors.
Date: November 8, 2004
Creator: Iglesias, C A
Partner: UNT Libraries Government Documents Department

Revisiting the total ion yield x-ray absorption spectra of liquid water microjets

Description: Measurements of the total ion yield (TIY) x-ray absorption spectrum (XAS) of liquid water by Wilson et al. (2002 J. Phys.: Condens. Matter 14 L221 and 2001 J. Phys. Chem. B 105 3346) have been revisited in light of new experimental and theoretical efforts by our group. Previously, the TIY spectrum was interpreted as a distinct measure of the electronic structure of the liquid water surface. However, our new results indicate that the previously obtained spectrum may have suffered from as yet unidentified experimental artifacts. Although computational results indicate that the liquid water surface should exhibit a TIY-XAS that is fundamentally distinguishable from the bulk liquid XAS, the new experimental results suggest that the observable TIY-XAS is actually nearly identical in appearance to the total electron yield (TEY-)XAS, which is a bulk probe. This surprising similarity between the observed TIY-XAS and TEY-XAS likely results from large contributions from x-ray induced electron stimulated desorption of ions, and does not necessarily indicate that the electronic structure of the bulk liquid and liquid surface are identical.
Date: February 16, 2008
Creator: Saykally, Richard J; Cappa, Chris D.; Smith, Jared D.; Wilson, Kevin R. & Saykally, Richard J.
Partner: UNT Libraries Government Documents Department

PG 0946+301: the Rosetta Stone of BALQSOs?

Description: We describe the motivation and features of a multiwavelength spectroscopic campaign on broad absorption line (BAL) QSO PG 0946+301. The main goal of this project is to determine the ionization equilibrium and abundances (IEA) in BAL outflows. Previous studies of IEA in BALQSOs were based on the assumption that the BALs are not saturated so that the column densities inferred from the apparent optical depths are realistic. This critical assumption is at odds with several recent observations and with analysis of existing data which indicate that the absorption troughs are heavily saturated even when they are not black. In addition, X-ray observations, which are important for constraining the ionizing continuum, were not available for those objects that had UV spectral data. Quantifying the level of saturation in the BALs necessitates UV spectroscopy with much higher S/N and broader-spectral coverage than currently exist. After taking into account the capabilities of available observatories, our best hope for a substantial improvement in understanding the IEA in BALQSOs is to concentrate considerable observational resources on the most promising object. Our studies of available HST and ground-based spectra show that PG 0946+301 is by far the best candidate for such a program. This BALQSO is at least five times brighter, shortward of 1000 {Angstrom}, rest frame, than any other object, and due to its low redshift it has an especially sparse Ly{alpha} forest. At the same time PG 0946+301 is a typical BALQSO and therefore its IEA should be representative. To this effect we are developing a multiwavelength spectroscopic campaign (UV, FUV, X-ray and optical) on BALQSO PG 0946+301. We discuss the goals and feasibility of each observational component: HST, FUSE, ASCA and ground-based.
Date: June 1, 1998
Creator: Arav, N., LLNL
Partner: UNT Libraries Government Documents Department

IR Properties of Ge-Doped CH - A Continuation

Description: We have reexamined Ge-doped CH and have found that the material is more reactive to air than previously understood. The Ge-doped material as formed shows by IR the presence of a Ge-H linkage that oxidizes rapidly, giving rise to a significant OH absorption. This broad peak impacts IR layering wavelengths of interest.
Date: April 4, 2003
Creator: Cook, B; Nikroo, A & Czechowicz, D
Partner: UNT Libraries Government Documents Department

Solid Sorbents for CO2 Capture from Post-Combustion and Pre-Combustion Gas Streams

Description: A novel liquid impregnated solid sorbent was developed for CO2 removal in the temperature range of ambient to 60 °C for both fixed bed and fluidized bed reactor applications. The sorbent is regenerable at 60-80 °C. Multi-cycle tests conducted in an atmospheric bench scale reactor with simulated flue gas demonstrated that the sorbent retains its CO2 sorption capacity with CO2 removal efficiency of about 99%. A second, novel solid sorbent containing mixture of alkali earth and alkali compounds was developed for CO2 removal at 200-315 °C from high pressure gas streams (i.e., suitable for IGCC systems). The sorbent showed very high capacity for CO2 removal from gas streams containing 28% CO2 at 200 °C and 11.2 atm during lab-scale flow reactor tests as well as regenerability at 375 °C.
Date: August 1, 2007
Creator: Siriwardane, R.V.; Robinson, C. & Stevens, R.W.
Partner: UNT Libraries Government Documents Department

Interfacial electronic charge transfer and density of states in short period Cu/Cr multilayers

Description: Nanometer period metallic multilayers are ideal structures to investigate electronic phenomena at interfaces between metal films since interfacial atoms comprise a large atomic fraction of the samples. The Cu/Cr binary pair is especially suited to study the interfaces in metals since these elements are mutually insoluble, thus eliminating mixing effects and compound formation and the lattice mismatch is very small. This allows the fabrication of high structural quality Cu/Cr multilayers that have a structure which can be approximated in calculations based on idealized atomic arrangements. The electronic structure of the Cu and the Cr layers in several samples of thin Cu/Cr multilayers were studied using x-ray absorption spectroscopy (XAS). Total electron yield was measured and used to study the white lines at the Cu L{sub 2} and L{sub 3} absorption edges. The white lines at the Cu absorption edges are strongly related to the unoccupied d-orbitals and are used to calculate the amount of charge transfer between the Cr and Cu atoms in interfaces. Analysis of the Cu white lines show a charge transfer of 0.026 electrons/interfacial Cu atom to the interfacial Cr atoms. In the Cu XAS spectra we also observe a van Hove singularity between the L{sub 2} and L{sub 3} absorption edges as expected from the structural analysis. The absorption spectra are compared to partial density of states obtained from a full-potential linear muffin-tin orbital calculation. The calculations support the presence of charge transfer and indicate that it is localized to the first two interfacial layers in both Cu and Cr.
Date: July 1999
Creator: Barbee, T. W.; Bello, A. F.; Klepeis, J. E. & Van Buuren, T.
Partner: UNT Libraries Government Documents Department

X-ray absorption study of the electronic structure of Mn-doped amorphous Si

Description: The electronic structure of Mn in amorphous Si (a-Mn{sub x}Si{sub 1?x}) is studied by X-ray absorption spectroscopy at the Mn L{sub 3,2} edges for x = 0.005-0.18. Except the x = 0.005 sample, which shows a slight signature of Mn{sup 2+} atomic multiplets associated with a local Mn moment, all samples have broad and featureless L{sub 3,2} absorption peaks, corresponding to an itinerant state for all 3d electrons. The broad X-ray absorption spectra exclude the possibility of a localized 3d moment and explain the unexpectedly quenched Mn moment in this magnetically-doped amorphous semiconductor. Such a fully delocalized d state of Mn dopant in Si has not been previously suggested.
Date: March 8, 2008
Creator: Arenholz, Elke; Zeng, Li; Huegel, A.; Helgren, E.; Hellman, F.; Piamonteze, C. et al.
Partner: UNT Libraries Government Documents Department