Ion and Electron Momentum Distributions from Single and Double Ionization of Helium Induced by Compton Scattering

We present the momentum distributions of the nucleus and of the electrons from double ionization of the helium atom by Compton scattering of photons with hν=40  keV. We find that the doubly charged ion momentum distribution is very close to the Compton profile of the nucleus in the ground state of the helium atom, and the momentum distribution of the singly charged ion to give a precise image of the electron Compton profile. To reproduce these results, nonrelativistic calculations require the use of highly correlated initial- and final-state wave functions

Lower CSF oxytocin concentrations in women with a history of childhood abuse

Early-life disruption of the parent-child relationship, for example, in the form of abuse, neglect or loss, dramatically increases risk for psychiatric, as well as certain medical, disorders in adulthood. The neuropeptide oxytocin (OT) plays a seminal role in mediating social affiliation, attachment, social support, maternal behavior and trust, as well as protection against stress and anxiety. We therefore examined central nervous system OT activity after early-life adversity in adult women. We measured OT concentrations in cerebrospinal fluid (CSF) collected from 22 medically healthy women, aged 18-45 years, categorized into those with none-mild versus those with moderate-severe exposure to various forms of childhood abuse or neglect. Exposure to maltreatment was associated with decreased CSF OT concentrations. A particularly strong effect was identified for emotional abuse. There were inverse associations between CSF OT concentrations and the number of exposure categories, the severity and duration of the abuse and current anxiety ratings. If replicated, the association of lower adult CSF OT levels with childhood trauma might indicate that alterations in central OT function may be involved in the adverse outcomes of childhood adversity

Nachweis und Charakterisierung von rissartigen Fehlern im Plattierungsbereich

The possibility of characterising defects in the surface of plated components was investigated in a BAM project. Measurements were to show whether defects were at the surface only, in the base material or plating only, or going through the protective coating into the base material. Defect detectability was investigated closer whenever a signal-noise difference of > 6 db was encountered. The findings will be taken into account in the new KTA rule 3201.4.Die im Rahmen dieses Vorhabens durchgefuehrten Arbeiten sollten Aufschluss darueber geben, ob und wie eine Charakterisierung von Fehlern im oberflaechennahen Bereich von plattierten Bauteilen moeglich ist. Anhand der aufgenommenen und verarbeiteten Messdaten soll eine Entscheidung ueber die Fehlerart zu treffen sein, d.h. darueber, ob Fehler 1. zur Oberflaeche geoeffnet sind, 2. nur in der Plattierung oder im Grundwerkstoff liegen, oder 3. durch die Plattierung in das Grundmaterial reichen. Bei den BAM - Untersuchungen wurde die Fehlernachweisbarkeit immer dann naeher betrachtet, wenn der Signal-Rausch-Abstand ca. >6 dB war. Die Ergebnisse dieses Untersuchungsvorhabens sollen bei der Ueberarbeitung der KTA-Regel 3201.4 mit einfliessen. (orig.)Available from TIB Hannover: RO 3190(2003-617) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Recoil-Induced Asymmetry of Nondipole Molecular Frame Photoelectron Angular Distributions in the Hard X-ray Regime

We investigate angular emission distributions of the 1s photoelectrons of N2 ionized by linearly polarized synchrotron radiation at hν=40  keV. As expected, nondipole contributions cause a very strong forward-backward asymmetry in the measured emission distributions. In addition, we observe an unexpected asymmetry with respect to the polarization direction, which depends on the direction of the molecular fragmentation. In particular, photoelectrons are predominantly emitted in the direction of the forward nitrogen atom. This observation cannot be explained via asymmetries introduced by the initial bound and final continuum electronic states of the oriented molecule. The present simulations assign this asymmetry to a novel nontrivial effect of the recoil imposed to the nuclei by the fast photoelectrons and high-energy photons, which results in a propensity for the ions to break up along the axis of the recoil momentum. The results are of particular importance for the interpretation of future experiments at x-ray free electron lasers operating in the few tens of keV regime, where such nondipole and recoil effects will be essential

Photon-Momentum-Induced Molecular Dynamics in Photoionization of N₂ at hν = 40 keV

We investigate K-shell ionization of N2 at 40 keV photon energy. Using a cold target recoil ion momentum spectroscopy reaction microscope, we determine the vector momenta of the photoelectron, the Auger electron, and both N+ fragments. These fully differential data show that the dissociation process of the N2+2 ion is significantly modified not only by the recoil momentum of the photoelectron but also by the photon momentum and the momentum of the emitted Auger electron. We find that the recoil energy introduced by the photon and the photoelectron momentum is partitioned with a ratio of approximately 30∶70 between the Auger electron and fragment ion kinetic energies, respectively. We also observe that the photon momentum induces an additional rotation of the molecular ion