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Transition probabilities have been measured between the low-lying yrast states in 175Au by employing the recoil distance Doppler-shift method combined with the selective recoil-decay tagging technique. Reduced transition probabilities and magnitudes of transition quadrupole moments have been extracted from measured lifetimes allowing dramatic changes in nuclear structure within a low excitation-energy range to probed. The transition quadrupole moment data are discussed in terms of available systematics as a function of atomic number and aligned angular momentum.

The SAGE spectrometer combines a high-efficiency γ-ray detection system with an electron spectrometer. Some of the design features have been known to be problematic and surprises have come up during the early implementation of the spectrometer. Tests related to bismuth germanate Compton-suppression shields, electron detection efficiency and an improved cooling system are discussed in the paper.

The influence of non-radiative recombination on the photoluminescence decay time (τPL) has been studied for GaInNAs/GaAs quantum wells with Ga- and In-rich environments of N atoms. At low temperatures, this influence is suppressed, due to the carrier localization phenomenon, which leads to a spectral dispersion of τPL. For investigated samples, this dispersion has been found to be in the range of ~0.2–2.0 ns. With the temperature increase, the free exciton emission starts to dominate instead of the localized exciton emission and the dispersion of τPL disappears. The dynamic of free exciton recombination is strongly influenced by the non-radiative recombination, which varies between samples, due to different concentration of non-radiative centers. The study of influence of non-radiative recombination on τPL has been performed at 180 K, since this temperature is high enough to eliminate the localized emission and activate non-radiative recombination and low enough to observe excitonic emission without stron...

The chain of Barium isotopes enables us to study experimentally the evolution of nuclear quadrupole collectivity from the shell closure at N = 82 towards neutron-deficient or neutron-rich deformed nuclei. The TU Darmstadt group has investigated several nuclei from stable 130;132 Ba up to radioactive 140;142 Ba with the projectile-Coulomb excitation technique including the use of the Doppler-shift attenuation method (DSAM). Lifetimes of quadrupole-collective states of 132 Ba and 140 Ba were obtained for the first time as well as the static electric quadrupole moments Q(2 + ) for 130;132 Ba and 140;142 Ba. The results are compared to Monte Carlo shell model and Beyond-Mean-Field calculations. The phenomenon of shell stabilization in the N = 80 isotones is further investigated by measurements of the B(E2;2 + ! 0 + ) values of 140 Nd and 142 Sm and comparison to the quasi-particle phonon model and shell-model calculations.

Lifetimes of the low-lying excited states in the very neutron-deficient nucleus ${}^{175}$Au have been measured by the recoil-distance Doppler-shift method using $\ensuremath{\gamma}$-ray spectra obtained with the recoil-decay tagging technique. Transition quadrupole moments and reduced transition probabilities extracted for this odd-$Z$ nucleus indicate the existence of three different shapes and the competition between collective and noncollective structures.

The energy fine structure, corresponding to different nitrogen nearest-neighbor environments, was observed in contactless electroreflectance (CER) spectra of as-grown GaInNAs quantum wells (QWs) obtained at various As/III pressure ratios. In the spectral range of the fundamental transition, two CER resonances were detected for samples grown at low As pressures whereas only one CER resonance was observed for samples obtained at higher As pressures. This resonance corresponds to the most favorable nitrogen nearest-neighbor environment in terms of the total crystal energy. It means that the nitrogen nearest-neighbor environment in GaInNAs QWs can be controlled in molecular beam epitaxy process by As/III pressure ratio.

We present a simplified method to employ laser interference lithography for the fabrication of ordered nanostructures. Neither resist, nor an elaborate fabrication process was needed. Four-beam interference patterns generated in this work included periodic arrays of holes in GaAs, covered with SiO(2) bubbles, and they were directly written into the sample. The diameters of the smallest holes were less than 30 nm. We propose a model to interpret the results.

The authors report on an interesting observation regarding thermal annealing of a beryllium-doped Ga0.65In0.35As0.99N0.01/GaAs quantum well (QW) grown by molecular beam epitaxy. A QW doped at 6×1019 cm−3 exhibited superior thermal properties and about six times larger photoluminescence than an undoped QW of the same structure. X-ray diffraction and secondary ion mass spectrometry provided evidence that beryllium suppressed indium diffusion and stabilized (metastable) dilute nitride heterostructure upon annealing.

The effects of thermal annealing on GaInAs∕GaAs and GaInAsN∕GaAs quantum wells, grown by molecular beam epitaxy, were investigated. Optical and structural properties were examined upon annealing when the samples had a 200nm thick SiO2 cap layer, or were placed in a so-called GaAs box or were left uncapped. The GaAs box gave rise to the strongest photoluminescence without significant blueshift or structural changes at moderate annealing temperature. Capping with SiO2 impaired the samples and caused a more pronounced blueshift for the GaInAs quantum wells than for the GaInAsN ones. These results consolidate our understanding of the blueshift mechanisms.

Bismuth (Bi) is a surfactant which controls the electronic and structural properties of epitaxially grown GaInAs and GaInP alloys. The authors have studied Bi-terminated surfaces of GaInAs(100) layers, deposited onto InP(100) substrates, by means of scanning tunneling microscopy and spectroscopy and x-ray photoelectron spectroscopy. It appears that Bi stabilizes an interesting (2×1) surface reconstruction on GaInAs(100). Under certain conditions, this reconstruction undergoes a phase transition to (2×4), which has about one-half of the Bi content of the (2×1) surface. Based on the experimental findings, they discuss mechanisms leading to this phase transition.

Valence band electronic structure of mixed uranium oxides (UO2, U4O9, U3O7, U3O8, UO3) has been studied by the resonant inelastic X-ray scattering (RIXS) technique at the U M5 edge and by computational methods. We show here that the RIXS technique and recorded U 5f-O 2p charge transfer excitations can be used to proof the validity of theoretical approximations, Chem Commun (2018)

A new plunger device has been designed and built to measure the lifetimes of unbound states in exotic nuclei beyond the proton drip-line. The device is designed to work in both vacuum and dilute-gas environments made possible through the introduction of a lowvoltage piezoelectric motors. The differential plunger for unbound nuclear states, DPUNS, will be used in conjunction with the gas-filled separator RITU and the vacuum separator MARA at the accelerator laboratory of the University of Jyvaskyla, Finland, to measure the lifetimes of excited states with low population cross-sections. This is achieved by eliminating the need for a carbon foil to isolate the helium gas of RITU from the beam line thus reducing the background from beam-foil reactions. The plunger will be used to address many key facets of nuclear structure physics with particular emphasis on the effect of deformation on proton emission rates.

Semantic segmentation is the task of assigning a class or label to every pixel of the image. In addition to detecting objects, the semantic segmentation models also predict the shape, size, and location of each object in images. Deep learning-based segmentation has been used in challenging object detection tasks in several domains, such as autonomous vehicles, satellite images, and medical image diagnostics.Within materials science, timely and reliable detection of creep voids in solid materials operating under high temperatures is vital for better life cycle management of valuable components. In this study, we present the application of a semantic image segmentation model for detecting creep voids in SEM images.The semantic segmentation models generally consist of an encoder network followed by a decoder network. The encoder is usually a pre-trained classification network, such as VGG or ResNet. The decoder network projects the discriminative features learned by the encoder onto the pixel space, performing the classification task. To distinguish the creep voids from the normal surface of copper samples, we applied the DeepLab-v3+ model with encoders pre-trained on large datasets. Training the model with only 250 images for 200 epochs, we obtained a mean IoU score of 0.994 and a dice loss of 0.003. The generated segmentation maps provide information about the area fraction and number of creep voids.

Metallic high-temperature structures are subject to creep. Creep means significant viscous time-dependent and liquid-like material flow in the direction of the principal stress leading eventually to component failure. One important manifestation of creep is the voids at the grain boundaries of the material. The reliable and accurate detection of creep void density and the size of voids is an important step to improve the high-temperature component lifecycle management.Usually creep void analysis in service conditions is performed by replica inspection. The interpretation of the results can often be difficult and time-consuming. Large number of voids makes density and size analysis challenging and increases possibility of human misinterpretation. We show that AI-based creep void detection removes these obstacles by quickly processing large number of sample images with high detection accuracy.Computer vision (CV), a field of artificial intelligence (AI), has been utilized in industries ranging from energy to manufacturing to, e.g., detect issues in products and processes based on image and video data. Object detection aspect of CV focuses on detection and identification of objects in an image or video, such as face detection and damage identification in machines.We applied the YOLOv5s model with its default configuration and pretrained weights on scanning electron microscope (SEM) images of oxygen-free phosphorus-doped copper sample surfaces containing creep voids. Each of the 40 high-resolution SEM images was split into four smaller images and annotated with online tool CVAT. The model was trained using 160 images, and satisfactory mean average precision of 0.82 was achieved. By adjusting the confidence threshold, the model predicts all the creep voids in test images correctly. The trained model outputs coordinates of the voids in the images and cropped images that contain only the voids, which can be used to calculate the void density and sizes.

The spectroscopy and structure of excited states of N similar to Z nuclei in the mass 70-100 region has been investigated using two techniques. In the A similar to 70-80 region fusion evaporation reactions coupled with the recoil-beta-tagging method have been employed at Jyvaskyla to study low-lying states in odd-odd N = Z nuclei. Results from these and other data for known odd-odd nuclei above mass 60 will be discussed. In the heavier mass 90 region a fragmentation experiment has been performed using the RIS-ING/FRS setup at GSI. This experiment was primarily aimed at searching for spin gap isomers in nuclei around A similar to 96. The objectives of the latter experiment will be discussed.

A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain E2 and M1 transition matrix elements of Nd-140 using the multistep Coulomb-excitation code GOSIA. The absolute M1 strengths, B(M1; 2(2)(-) -> 2(1)(+)) = 0.033(8)mu(2)(N), B(M1 ; 2(3)(+) -> 2(1)(+)) = 0.26(-0.10)(+0.11)mu(2)(N), and B(M1; 2(4)+ -> 2(1)(+))