The impact of a highly charged ion onto a solid gives rise to charge exchange between the ion and target atoms, so that a slow ion gets neutralized in the vicinity of the surface. Using highly charged Ar and Xe ions and the surface-only material graphene as a target, we show that the neutralization and deexcitation of the ions proceeds on a sub-10 fs time scale. We further demonstrate that a multiple Interatomic Coulombic Decay (ICD) model can describe the observed ultrafast deexcitation. Other deexcitation mechanisms involving nonradiative decay and quasimolecular orbital formation during the impact are not important, as follows from the comparison of our experimental data with the results of first-principles calculations. Our method also enables the estimation of ICD rates directly.

Titanium dioxide (TiO₂) in the form of thin films has attracted enormous attention for photocatalysis. It combines the fundamental properties of TiO₂ as a large bandgap semiconductor with the advantage of thin films, making it competitive with TiO₂ powders for recycling and maintenance in photocatalytic applications. There are many aspects affecting the photocatalytic performance of thin film structures, such as the nanocrystalline size, surface morphology, and phase composition. However, the quantification of each influencing aspect needs to be better studied and correlated. Here, we prepared a series of TiO₂ thin films using a sol-gel process and spin-coated on p-type, (100)-oriented silicon substrates with a native oxide layer. The as-deposited TiO₂ thin films were then annealed at different temperatures from 400 °C to 800 °C for 3 h in an ambient atmosphere. This sample synthesis provided systemic parameter variation regarding the aspects mentioned above. To characterize thin films, several techniques were used. Spectroscopic ellipsometry (SE) was employed for the investigation of the film thickness and the optical properties. The results revealed that an increasing annealing temperature reduced the film thickness with an increase in the refractive index. Atomic force microscopy (AFM) was utilized to examine the surface morphology, revealing an increased surface roughness and grain sizes. X-ray diffractometry (XRD) and UV-Raman spectroscopy were used to study the phase composition and crystallite size. The annealing process initially led to the formation of pure anatase, followed by a transformation from anatase to rutile as the annealing temperature increased. An overall enhancement in crystallinity was also observed. The photocatalytic properties of the thin films were tested using the photocatalytic decomposition of acetone gas in a home-built solid (photocatalyst)–gas (reactant) reactor. The composition of the gas mixture in the reaction chamber was monitored using in situ Fourier transform infrared spectroscopy. Finally, all of the structural and spectroscopic characteristics of the TiO₂ thin films were quantified and correlated with their photocatalytic properties using a correlation matrix. This provided a good overview of which film properties affect the photocatalytic efficiency the most.

This paper presents an overview of experimental results and progress made in investigating density control using Li-coating, transport and L–H transitions in TJ-II. The Li-coating changes drastically the plasma–wall interaction, decreasing the recycling, and enlarges substantially the operational range of the device delaying the appearance of radiative collapse that happens for higher densities, which permits confinement properties of much denser plasmas to be studied. Moreover, L–H mode transition has only been achieved after Li-coating in TJ-II. The effect of rational surfaces on heat transport is studied showing a decrease in heat diffusivity close to their position, and it is also seen that rational surfaces located in the edge make L–H transition easier. TJ-II findings provide a new guideline for understanding the trigger mechanism of the L–H transition pointing out the importance of low frequency fluctuating sheared E × B flows. The properties of fast-ion confinement are described as well as the effects of impurities on radiation profiles, showing two types of profiles the bell and the dome shape, the latter being more prone to radiative collapse.

Fluorescence yields (FYs) for the Ge $L$ shell were determined by a theoretical and two experimental groups within the framework of the International Initiative on X-Ray Fundamental Parameters Collaboration. Calculations were performed using the Dirac-Fock method, including relativistic and QED corrections. The experimental value of the $L_3\mathrm{FY}{\omega }_{L_3}$ was determined at the Physikalisch-Technische Bundesanstalt undulator beamline of the synchrotron radiation facility BESSY II in Berlin, Germany, and the $L{\alpha }_{1,2}$ and $L{\beta }_1$ line widths were measured at the Swiss Light Source, Paul Scherrer Institute, Switzerland, using monochromatized synchrotron radiation and a von Hamos x-ray crystal spectrometer. The measured fluorescence yields and line widths are compared to the corresponding calculated values.

Fluorescence yields are one of the fundamental parameters in atomic physics and related areas. Despite the increase of experimental work in the last decade, to obtain values of $K$-shell fluorescence yields available data are scarce or outdated for many elements. The available theoretical results cannot fill the gap since quite often they are derived from semi-empirical calculations based on old models. This is the case of Ge that has many applications in science. In this work, we present the results of a collaboration between an experimental and a theoretical group to obtain the decay rates and fluorescence yields for Ge. The calculations were performed within the Dirac-Fock method, including relativistic and QED corrections, using a state-of-the-art approach. The experimental work was carried out at the SOLEIL synchrotron and the fluorescence yields were measured by two distinct methods: the reflection geometry method and the escape peak method. The results show a very good agreement between the experiment and theory (1.1%), well within the experimental uncertainty (2.4%).

Plasmonics using metal nanoparticles (MNPs) has emerged as an important research subject in the field of photonics, electronics, and nanotechnology. Despite spectacular progress in recent years, accurate tuning and modeling of plasmon resonances over a wide spectral range using state-of-the-art fabrication methods are still challenging tasks. Here, we report on the fine-tuning of the localized surface plasmon resonance (LSPR) of metal nanoparticles over a wide spectral range from near-infrared to blue using nanosphere lithography (NSL). In this systematic study, we use NSL to fabricate triangular shaped metal nanostructures using gold, silver, copper, and aluminum. All structures were annealed up to 500 °C under a nitrogen atmosphere in order to study the effect of annealing on the LSPR. Structural changes were investigated using scanning electron microscopy and atomic force microscopy. UV-VIS spectroscopy was used to determine the LSPR spectral position for these structures. The LSPR peak position is ordered as copper, gold, silver, and aluminum (from low to high photon energy—ranging from near-infrared to blue). The rate at which the LSPR changes with respect to the increasing annealing temperature is determined to be (2.3 ± 0.3) nm/°C and (1.3 ± 0.1) nm/°C for Ag and Au, respectively, while Cu MNPs show a two-step relation with a steeper slope of (1.4 ± 0.3) nm/°C initially up to 275 °C followed by a shallower slope of (0.5 ± 0.1) nm/°C. The full width at half maximum of the LSPR increases from gold over silver and copper to aluminum. We also performed finite element method simulations to validate the experimental findings. Our results can have a significant impact in plasmonic applications where fine-tuning and accurate designing of the LSPR are important.