New insights into the electronic structure ofα-U andδ-Pu.

This work presents the results of a theoretical study of the electronic structure of two actinide metals,α-U andδ-Pu. We compare ourab-initioresults obtained with the recently developed self-consistent Vertex corrected GW approach with previously published experimental measurements such as photo-electron spectroscopy, for the occupied density of states, and bremsstralung isochromat spectroscopy (BIS) and inverse photo-electron spectroscopy (IPES), for the unoccupied density of states. Ourab-initioapproach includes all important relativistic effects (it is based on Dirac's equation) and it represents the first application of the Vertex corrected GW approach in the physics of actinides. Overall, our theoretical results are in good agreement with the experimental data, which supports the level of approximations which our theoretical method is based upon. By comparing our vertex corrected GW results with our results obtained with less sophisticated approaches (local density approximation and self-consistent GW) we differentiate the strength of correlation effects in Uranium and Plutonium. Also, our theoretical results allow us to elucidate the subtle differences between the previously published experimental BIS and IPES data on the unoccupied density of states inα-U.

Pu 5f Occupation in Plutonium Dioxide.

An actinide N4,5 branching ratio analysis of PuO2 and UO2 has been performed, including measurements with a scanning transmission electron microscope at the Advanced Light Source. It is shown that the 5f occupation of the Pu in plutonium dioxide is n = 5. This is contrary to recent results from another technique.

5f covalency from x-ray resonant Raman spectroscopy.

X-ray resonant Raman spectroscopy (XRRS), a variant of resonant inelastic x-ray scattering, has been used to investigate the two prototype systems, UF4and UO2. Both are U5f2and each is an example of 5f localized, ionic behavior and 5f localized, covalent behavior, respectively. From the M5XRRS measurements, the 5f band gap in each can be directly determined and, moreover, a clear and powerful sensitivity to 5f covalency emerges.

Orbital specificity in the unoccupied states of UO2 from resonant inverse photoelectron spectroscopy.

One of the crucial questions of all actinide electronic structure determinations is the issue of 5f versus 6d character and the distribution of these components across the density of states. Here, a breakthough experiment is discussed, which has allowed the direct determination of the U5f and U6d contributions to the unoccupied density of states in uranium dioxide. A novel resonant inverse photoelectron and x-ray emission spectroscopy investigation of UO(2) is presented. It is shown that the U5f and U6d components are isolated and identified unambiguously.

An instrument for the investigation of actinides with spin resolved photoelectron spectroscopy and bremsstrahlung isochromat spectroscopy.

A new system for spin resolved photoelectron spectroscopy and bremsstrahlung isochromat spectroscopy has been built and commissioned at Lawrence Livermore National Laboratory for the investigation of the electronic structure of the actinides. Actinide materials are very toxic and radioactive and therefore cannot be brought to most general user facilities for spectroscopic studies. The technical details of the new system and preliminary data obtained therein will be presented and discussed.

Spin resolved photoelectron spectroscopy of Fe(3)O(4): the case against half-metallicity.

Many materials have been theoretically predicted to be half-metallic, and hence suitable for use as pure spin sources in spintronic devices. Yet to date, remarkably few of these predictions have been experimentally verified. We have used spin polarized photoelectron spectroscopy to study one candidate half-metallic system, Fe(3)O(4). Such experiments are normally hampered by difficulties in producing clean stoichiometric surfaces with a polarization that is truly representative of that of the bulk. However, by utilizing higher photon energies than have traditionally been used for such experiments, we can study polarization in 'as received' samples, essentially 'looking through' the disrupted surface. High quality, strain relieved, ex situ prepared Fe(3)O(4) films have been thoroughly characterized by diffraction, transport and magnetometry studies of their crystallographic, electronic and magnetic properties. The spectroscopic results are found to agree fairly closely with previously published experimental data on in situ grown thin films and cleaved single crystals. However, despite the higher photoelectron kinetic energies of the experiment, it has not been possible to observe 100% polarization at the Fermi level. Hence, our data do not support the claim of true half-metallicity for Fe(3)O(4).

Probing the population of the spin-orbit split levels in the actinide 5f states.

Spin-orbit interaction in the 5f states is believed to strongly influence exotic behaviors observed in actinide metals and compounds. Understanding these interactions and how they relate to the actinide series is of considerable importance. To address this issue, the branching ratio of the white-line peaks of the N4,5 edge for the light actinide metals, alpha-Th, alpha-U, and alpha-Pu were recorded using electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM) and synchrotron-radiation-based X-ray absorption spectroscopy (XAS). Using the spin-orbit sum rule and the branching ratios from both experimental spectra and many-electron atomic spectral calculations, accurate values of the spin-orbit interaction, and thus the relative occupation of the j = 5/2 and 7/2 levels, are determined for the actinide 5f states. Results show that the spin-orbit sum rule works very well with both EELS and XAS spectra, needing little or no correction. This is important, since the high spatial resolution of a TEM can be used to overcome the problems of single-crystal growth often encountered with actinide metals, allowing acquisition of EELS spectra, and subsequent spin-orbit analysis, from nm-sized regions. The relative occupation numbers obtained by our method have been compared with recent theoretical results and they show a good agreement in their trend.

Applicability of the spin-orbit sum rule for the actinide 5f states.

The branching ratio of core-valence transitions in electron energy-loss spectroscopy and x-ray absorption spectroscopy is linearly related to the expectation value of the spin-orbit operator of the valence states. Here, we analyze the branching ratio of the N(4,5) edges in the actinides and find that the spin-orbit sum rule gives an accurate result without the need to include the core-valence interactions. The branching ratio is not only useful to study the variations in the 5f spin-orbit interaction, it also allows us to constrain the 5f count for given angular-momentum coupling conditions.

Failure of Russell-Saunders coupling in the 5f states of plutonium.

Using high energy-electron energy loss spectroscopy, transmission electron microscopy, and synchrotron-radiation-based x-ray absorption spectroscopy, we provide the first experimental evidence that Russell-Saunders (LS) coupling fails for the 5f states of Pu. These results support the assumption that only the use of jj or intermediate coupling is appropriate for the 5f states of Pu. High energy-electron energy loss spectroscopy experiments were performed by use of a transmission electron microscope and are coupled with image and diffraction data; therefore, the measurements are completely phase specific.

Spin-resolved photoemission of surface states of W(110)-(1 x 1)H.

The surface electronic states of W(110)-(1 x 1)H have been measured using spin- and angle-resolved photoemission. We directly demonstrate that the surface bands are both split and spin-polarized by the spin-orbit interaction in association with the loss of inversion symmetry near a surface. We observe 100% spin polarization of the surface states, with the spins aligned in the plane of the surface and oriented in a circular fashion relative to the Smacr; symmetry point. In contrast, no measurable polarization of nearby bulk states is observed.

Three unusual cases of multiple suicidal gunshot wounds to the head.

We describe three unusual cases of suicide involving multiple gunshot wounds, in which all of the victims suffered gunshot wounds to the head, yet none was rendered immediately incapacitated. Injuries were confined to the same area in two of the cases and were located in different areas in the other case. Two of the cases initially appeared to be homicides rather than suicides.

Traumatic seromuscular rupture of intestine: the acute and chronic forms.

BACKGROUND: Traumatic seromuscular rupture of intestine in the acute form is recognized by surgeons and pathologists and has received mention in the medical literature. The authors encountered two cases of this lesion presenting in the chronic form, in one case initially going unrecognized, both in battered children. To our knowledge, the chronic form of the injury has not been previously described in the literature. Three lesions in the acute stage were used to analyze the evolutionary stages of the chronic presentation. METHODS: The two chronic cases are described, together with gross and microscopic photographs. Three acute lesions are also described, with illustrations, two in battered children and one in a pedestrian/vehicle fatality. RESULTS: The three acute cases illustrate the pathogenesis and gradation of the injury that, in the absence of surgical therapy, will develop into the chronic lesion. The two chronic case descriptions illustrate the gross and microscopic pathology and the pathognomonic features. CONCLUSION: Seromuscular rupture of the intestine, when left untreated, develops in time into a lesion that may appear cryptogenic to the surgeon or the pathologist. This paper defines that lesion and its pathogenesis.