Laboratory von H\'amos X-ray Spectroscopy for Routine Sample Characterization

High energy resolution, hard X-ray spectroscopies are powerful element selective probes of the electronic and local structure of matter, with diverse applications in chemistry, physics, biology and materials science. The routine application of these techniques is hindered by the complicated and slow access to synchrotron radiation facilities. Here we propose a new, economic, easily operated laboratory high resolution von H\'amos type X-ray spectrometer, which offers rapid transmission experiments for X-ray absorption, and is also capable of recording X-ray emission spectra. The use of a cylindrical analyzer crystal and a position sensitive detector enabled us to build a maintenance free, flexible setup with low operational costs, while delivering synchrotron grade signal to noise measurements in reasonable acquisition times. We demonstrate the proof of principle and give examples for both measurement types. Finally, tracking of a several day long chemical transformation, a case better suited for laboratory than synchrotron investigation, is also presented

Body-related shame or guilt? Dominant factors in maladaptive eating behaviors among Hungarian and Norwegian university students

The main purpose of our study was to examine the psychometric properties of Conradts' Weight- and Body-Related Shame and Guilt Scale (WEB-SG) and associations of body shame and guilt with maladaptive eating behaviors and general chronic shame among Hungarian and Norwegian university students. Therefore, we collected data from 561 university students from both nations in a cross-sectional questionnaire study. Participants completed the following standardized self-report questionnaires in this online survey: WEB-SG, Eating Attitude Test-26 (EAT-26) and Experience of Shame Scale (ESS). We tested the measurement model of the WEB-SG with confirmatory factor analysis (CFA), and we performed CFA with covariates analysis to examine the association between WEB-guilt (WEB-G) and WEB-shame (WEB-S) and predictors. Our empirical model of WEB-SGhas adequate fit with Conradts' theoretical model among both samples. The body-related guilt positively associated with dieting and negatively related to oral control in both groups. We found a significant positive relationship between WEB-S and BMI in Hungarian sample. According to our results, WEB-SG is an adequate questionnaire for assessing weight and body-related shame and guilt in Hungarian and Norwegian non-clinical samples. Maladaptive weight and body-related guilt could be a relevant factor in proneness to anorexia. Our results highlight WEB-G and WEB-S as two critical factors in the assessment and treatment of eating difficulties

Angular dependence of core hole screening in LiCoO2: A DFT+U calculation of the oxygen and cobalt K-edge x-ray absorption spectra

Angular dependent core-hole screening effects have been found in the cobalt K-edge x-ray absorption spectrum of LiCoO2, using high-resolution data and parameter-free GGA+U calculations. The Co 1s core-hole on the absorber causes strong local attraction. The core-hole screening on the nearest neighbours cobalt induces a 2 eV shift in the density of states with respect to the on-site 1s-3d transitions, as detected in the Co K pre-edge spectrum. Our DFT+U calculations reveal that the off-site screening is different in the out-of-plane direction, where a 3 eV shift is visible in both calculations and experiment. The detailed analysis of the inclusion of the core-hole potential and the Hubbard parameter U shows that the core-hole is essential for the off-site screening, while U improves the description of the angular dependent screening effects. In the case of oxygen K-edge, both the core-hole potential and the Hubbard parameter improve the relative positions of the spectral features

Screening in YBCO at large wave vectors

We present experimental inelastic x-ray scattering (IXS) and ab initio time-dependent density-functional-theory (TDDFT) studies of YBa2Cu3O7-{\delta}. The response of the low-lying Ba 5p and Y 4p core electrons is shown to interact strongly with the Cu 3d and O 2p excitations, with important consequences on screening. The agreement between IXS and TDDFT results is excellent, apart from a new type of excitations, mainly related to loosely bound Ba electrons and significantly affected by correlations. This points to correlation mechanisms not fully described by TDDFT that might have a role in giving rise to antiscreening.Comment: 6 pages, 3 figure

On the microscopic origin of the magneto-electronic phase separation in Sr doped LaCoO3

The nanoscopic magneto-electronic phase separation in doped La1-xSrxCoO3 perovskites was studied with local probes. The phase separation is directly observed by M\"ossbauer spectroscopy in the studied doping range of 0.05 <= x <= 0.25 both at room-temperature as well as in the low temperature magnetic phase. Extended with current synchrotron based X-ray spectroscopies, these data help to characterize the volume as well as the local electric and magnetic properties of the distinct phases. A simple model based on a random distribution of the doping Sr ions describes well both the evolution of the separated phases as well as the variation of the Co spin state. The experiments suggest that Sr doping initiates small droplets and a high degree of doping driven cobalt spin-state transition, while the Sr-free second phase vanishes rapidly with increasing Sr content