Oxidation of carbon monoxide over Ag (111) by preadsorbed active oxygen studied by XPS and UPS

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Comparative experimental study of x-ray absorption spectroscopy and electron energy loss spectroscopy on passivated U surfaces

X-ray absorption spectroscopy and electron energy loss spectroscopy are complementary analytical techniques on energy and spatial resolution. These techniques are based on the same fundamental physical process of core excitation with either an incident photon or incident electron. In the proper experimental configuration the electron and photon inelastic scattering amplitudes are comparable and thus the x-ray and electron absorption edges look identical. We have applied these two complementary analytical techniques to investigate the electronic structure of C ion implanted U. Implantation of C{sup +} ions into U{sup 238} has been shown to produce a physically and chemically modified surface layer that passivates the surface preventing further air oxidation and corrosion. Comparison of the resultant spectra reveal that transitions between the initial state and a series of final states yield numerous strong features at the absorption edge that can provide structural information and information on the local chemical environment, including the character of the U 5f state

Hydrogen adsorption on Pd(133) surface

In this study used is an approach based on measurements of the total energy distribution (TED) of field emitted electrons in order to examine the properties of Pd (133) from the aspect of both hydrogen adsorption and surface hydrides formation. The most favourable sites offered to a hydrogen atom to be adsorbed have been indicated and an attempt to describe the peaks of the enhancement factor R spectrum to the specific adsorption sites has also been made.Comment: to be submitted to the Centr. Eur. J. Phy

The lowa farmer and world war II

World War II is the biggest fact in the Iowa farm situation. Though Iowa is far removed from air bombing and submarine torpedoing, it is on the battle front so far as economic and social effects of the war are concerned. Iowa’s commercial agriculture underwent terrific strain during and following World War I, and the pressures arising out of World War II promise to be similar, although less severe. It is the purpose of this report to estimate what some of these pressures will be. An understanding of the social and economic forces at work is necessary before plans can be made and action taken to ease the shock of war. The experience of the earlier war helps us to understand these forces, but that experience must be interpreted in light of the changed situation today

Summary Abstract: Adsorption of cyclohexane on Ru(001): A high resolution electron energy loss and UV-photoemission study

In the present work, we have investigated the adsorption of cyclohexane on Ru(001), using EELS (both in the specular and off-specular directions), angle-resolved photoelectron spectroscopy, and TDMS (combined in one UHV system) to investigate the orientation and symmetry of the adsorbed molecule and compare the results with the above-mentioned structural model [3]

Vibrational States of the Hydrogen Isotopes on Pd(111)

The ground and excited vibrational states for the three hydrogen isotopes on the Pd(111) surface have been calculated. Notable features of these states are the high degree of anharmonicity, which is most prominently seen in the weak isotopic dependence of the parallel vibrational transition, and the narrow bandwidths of these states, which imply that atomic hydrogen is localized on a particular surface site on time scales of 100 picoseconds or more. Experiments to resolve ambiguities concerning the present system are suggested.Comment: Surface Science Letters, 302, L305 (1994

Uranium passivation by C+ implantation: a photoemission and secondary ion mass spectrometry study

Implantation of 33 keV C{sup +} ions into polycrystalline U{sup 238} with a dose of 4.3 x 10{sup 17} cm{sup -2} produces a physically and chemically modified surface layer that prevents further air oxidation and corrosion. X-ray photoelectron spectroscopy and secondary ion mass spectrometry were used to investigate the surface chemistry and electronic structure of this C{sup +} ion implanted polycrystalline uranium and a non-implanted region of the sample, both regions exposed to air for more than a year. In addition, scanning electron microscopy was used to examine and compare the surface morphology of the two regions. The U 4f, O 1s and C 1s core-level and valence band spectra clearly indicate carbide formation in the modified surface layer. The time-of-flight secondary ion mass spectrometry depth profiling results reveal an oxy-carbide surface layer over an approximately 200 nm thick UC layer with little or no residual oxidation at the carbide layer/U metal transitional interface

Oxidation of uranium nanoparticles produced via pulsed laser ablation

An experimental apparatus designed for the synthesis, via pulsed laser deposition, and analysis of metallic nanoparticles and thin films of plutonium and other actinides was tested on depleted uranium samples. Five nanosecond pulses from a Nd:YAG laser produced films of {approx}1600 {angstrom} thickness that were deposited showing an angular distribution typical thermal ablation. The films remained contiguous for many months in vacuum but blistered due to induced tensile stresses several days after exposure to air. The films were allowed to oxidize from the residual water vapor within the chamber (2 x 10{sup -10} Torr base pressure). The oxidation was monitored by in-situ analysis techniques including x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) and followed Langmuir kinetics