Simultaneous Determination of Fe 3p Spin-Orbit and Exchange Splittings in Photoemission

Spin-resolved core-level photoemission data from the 3p level of ultrathin Fe films [1.4–5.1 monolayers (ML)] epitaxially grown on W(110) have been obtained. A nonlinear least-squares analysis, based on a one-particle Hamiltonian that simultaneously includes core-valence exchange and core-hole spin-orbit interactions, is developed. It is first tested on Fe 2p magnetic circular dichroism (MCD) photoemission spectra and shown to successfully describe the MCD asymmetry data. The model is then used to analyze our thin-film 3p data. With increasing film thickness the spin-orbit splitting (0.67±0.02 eV) remains constant (as expected), the exchange splitting increases from 0±0.12 eV to 0.41±0.05 eV, the average Fe film magnetization (=1.2±0.3μB at 1.4 ML) increases, and the singularity index decreases. The analysis highlights the importance of simultaneously considering all relevant photoemission parameters in extracting meaningful values of the spin-orbit and exchange interactions

Externally Dispersed Interferometry for Precision Radial Velocimetry

Externally Dispersed Interferometry (EDI) is the series combination of a fixed-delay field-widened Michelson interferometer with a dispersive spectrograph. This combination boosts the spectrograph performance for both Doppler velocimetry and high resolution spectroscopy. The interferometer creates a periodic spectral comb that multiplies against the input spectrum to create moire fringes, which are recorded in combination with the regular spectrum. The moire pattern shifts in phase in response to a Doppler shift. Moire patterns are broader than the underlying spectral features and more easily survive spectrograph blurring and common distortions. Thus, the EDI technique allows lower resolution spectrographs having relaxed optical tolerances (and therefore higher throughput) to return high precision velocity measurements, which otherwise would be imprecise for the spectrograph alone.Comment: 7 Pages, White paper submitted to the AAAC Exoplanet Task Forc

Surface Core-Level Shifts and Atomic Coordination at a Stepped W(110) Surface

Core-level 4f7/2 photoemission spectra have been measured from a single, bifacial W crystal, which has both a flat W(110) and a vicinal, stepped W(110) [W(320)] surface. This procedure reduces uncertainties in the quantitative description of peaks in the spectra from W(320). Various analyses, including nonlinear least-squares curve fitting, show that the average surface core-level shift (SCS) for W(320) is only ∼-140 meV, compared to -310 meV for W(110) and that, at a maximum, only two of five terrace rows are isoelectronic to W(110) surface atoms. The absence of a large SCS for the step-edge atoms contradicts earlier interpretations of W(320) core-level spectra and departs significantly from expectations based on atomic-coordination models or tight-binding calculations of a bulk truncated surface. We suggest that systematic errors are responsible for the differences in reported core-level shifts for W(320). Implications of possible step-edge-driven atomic rearrangements are discussed

Conduction-Electron Screening in the Bulk and at Low-Index Surfaces of Ta Metal

High-resolution core-level photoemission spectra from Ta(100) have been measured. The well-resolved peak from the first atomic layer allows a separate assessment of bulk and surface-layer screening responses: singularity indices αB=0.10±0.01 and α100=0.205±0.025, respectively, are obtained. The measured surface-atom lifetime broadening of 70±20 meV (compared to 37±5 meV in the bulk) is consistent with published Auger–photoemission coincidence measurements. The result for the bulk singularity index has been applied in the analysis of previous data in order to extract the screening response in the first atomic layer of Ta(111) (α111=0.16±0.01) and Ta(110) (α110=0.150±0.015). The trend in surface α’s implies an increasingly atomic character for the surface-layer atoms as one proceeds from Ta(110) to Ta(111) to Ta(100)

Thermally Induced Core-Electron Binding-Energy Shifts in Transition Metals: An ExperimentalInvestigation of Ta(100)

High-resolution photoemission spectra from the 4f7/2 levels of Ta(100) have been obtained between 77 K and room temperature. The data show an increase in both the surface and bulk core-level binding energies (BE’s) as the temperature is raised: between 77 and 293 K the bulk and surface BE’s increase by 31±3 and 13±2 meV, respectively. A model calculation of the bulk binding-energy increase, which is based upon the lattice expansion of the solid, is in good agreement with the experimental results and indicates that the shifts arise from both initial- and final-state effects that are of comparable magnitude. The model is further used to estimate thermally induced shifts for the whole 5d transition-metal series. © 1996 The American Physical Society

Low-cost point-focus solar concentrator, phase 1

The results of the preliminary design study for the low cost point focus solar concentrator (LCPFSC) development program are presented. A summary description of the preliminary design is given. The design philosophy used to achieve a cost effective design for mass production is described. The concentrator meets all design requirements specified and is based on practical design solutions in every possible way

Imaging White Light VISAR

An imaging white light velocimeter consisting of two imagine superimposing Michelson interferometers in series with the target interposed is demonstrated. Interferometrically measured 2-D velocity maps can be made of moving surfaces using unlimited bandwidth incoherent and extended area sources. Short pulse and broadband chirped pulse lasers can be used to provide temporal resolution not possible with monochromatic illumination. A 20 m/s per fringe imaging velociemter is demonstrated using an ordinary camera flash for illumination

An Imaging White Light Velocimeter

An imaging white light velocimeter consisting of 2 image superimposing Michelson interferometers in series with the target interposed is demonstrated. Interferometrically measured 2-D velocity maps can be made of moving surfaces using unlimited bandwith incoherent and extended source-area lamps. Short pulse and broadband chirped pulse lasers can be used to provide temporal resolution not previouslypossible with monochromatic illumination. A 20 m/x per fringe imaging velocimeter is demonstrated using an ordinary camera flash for illumination

Associations between multimorbidity and neuropathology in dementia: Consideration of functional cognitive disorders, psychiatric illness and dementia mimics

\ua9 The Author(s), 2024. Published by Cambridge University Press on behalf of Royal College of Psychiatrists.Background Multimorbidity, the presence of two or more health conditions, has been identified as a possible risk factor for clinical dementia. It is unclear whether this is due to worsening brain health and underlying neuropathology, or other factors. In some cases, conditions may reflect the same disease process as dementia (e.g. Parkinson\u27s disease, vascular disease), in others, conditions may reflect a prodromal stage of dementia (e.g. depression, anxiety and psychosis). Aims To assess whether multimorbidity in later life was associated with more severe dementia-related neuropathology at autopsy. Method We examined ante-mortem and autopsy data from 767 brain tissue donors from the UK, identifying physical multimorbidity in later life and specific brain-related conditions. We assessed associations between these purported risk factors and dementia-related neuropathological changes at autopsy (Alzheimer\u27s-disease related neuropathology, Lewy body pathology, cerebrovascular disease and limbic-predominant age-related TDP-43 encephalopathy) with logistic models. Results Physical multimorbidity was not associated with greater dementia-related neuropathological changes. In the presence of physical multimorbidity, clinical dementia was less likely to be associated with Alzheimer\u27s disease pathology. Conversely, conditions which may be clinical or prodromal manifestations of dementia-related neuropathology (Parkinson\u27s disease, cerebrovascular disease, depression and other psychiatric conditions) were associated with dementia and neuropathological changes. Conclusions Physical multimorbidity alone is not associated with greater dementia-related neuropathological change; inappropriate inclusion of brain-related conditions in multimorbidity measures and misdiagnosis of neurodegenerative dementia may better explain increased rates of clinical dementia in multimorbidit