Prediction of huge X-ray Faraday rotation at the Gd N_4,5 threshold

X-ray absorption spectra in a wide energy range around the 4d-4f excitation threshold of Gd were recorded by total electron yield from in-plane magnetized Gd metal films. Matching the experimental spectra to tabulated absorption data reveals unprecedented short light absorption lengths down to 3 nm. The associated real parts of the refractive index for circularly polarized light propagating parallel or antiparallel to the Gd magnetization, determined through the Kramers-Kronig transformation, correspond to a magneto-optical Faraday rotation of 0.7 degrees per atomic layer. This finding shall allow the study of magnetic structure and magnetization dynamics of lanthanide elements in nanosize systems and dilute alloys.Comment: 4 pages, 2 figures, final version resubmitted to Phys. Rev. B, Brief Reports. Minor change

Powder Bed Layer Characteristics: The Overseen First-Order Process Input

A discrete element powder model is used in conjunction with a finite volume melting model on the first layer of a powder bed selective laser melting process

Dynamic Acoustic Control of Individual Optically Active Quantum Dot-like Emission Centers in Heterostructure Nanowires

We probe and control the optical properties of emission centers forming in radial het- erostructure GaAs-Al0.3Ga0.7As nanowires and show that these emitters, located in Al0.3Ga0.7As layers, can exhibit quantum-dot like characteristics. We employ a radio frequency surface acoustic wave to dynamically control their emission energy and occupancy state on a nanosec- ond timescale. In the spectral oscillations we identify unambiguous signatures arising from both the mechanical and electrical component of the surface acoustic wave. In addition, differ- ent emission lines of a single quantum dot exhibit pronounced anti-correlated intensity oscilla- tions during the acoustic cycle. These arise from a dynamically triggered carrier extraction out of the quantum dot to a continuum in the radial heterostructure. Using finite element modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as the underlying mech- anism. These simulation results quantitatively reproduce the observed switching and show that in our systems these quantum dots are spatially separated from the continuum by > 10.5 nm.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright \c{copyright} American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/nl404043

Real-Time Monitoring of Powder Mixing Dynamics with Spectroscopic PAT-Tools

The aim of Process Analytical Technology (PAT) is to gain deeper insight in pharmaceutical manufacturing processes, [...

Evaluation of API-Distribution and Coating Thickness by NIR Spectroscopy and Raman Chemical Mapping

Spray coating is an important unit operation in the pharmaceutical industry. [...

Coupling ground penetrating radar and fluid flow modeling for oilfield monitoring applications

The recent introduction of smart well technology allows for new geophysical monitoring opportunities. Smart wells, which allow zonal production control, combined with monitoring techniques capable of capturing the arrival of undesired fluids, have the potential to significantly increase the oil recovery. We consider borehole radar as a valuable technology for monitoring of the near-well region. By coupling a drainage process of a bottom water-drive reservoir with electromagnetic simulations, we find that radar sensors located in the production well can successfully map the fluid saturation evolution. In low-conductivity reservoirs (<0.02 S/m), a system performance above 80 dB is necessary to record reflections in the range of 10 m. Higher conductivity values strongly reduce the radar investigation depth. Despite the technical challenges to implement a permanent down-hole radar system, the potential semi-continuous acquisition would make 4D ground-penetrating radar a promising technology in capturing the near-well fluid dynamics. Suitable environments are bottom water-drive reservoirs with thin oil layer and heavy oil reservoirs exploited by steam-assisted gravity drainage processes.Geoscience & EngineeringCivil Engineering and Geoscience