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It is known that rare-earth-based pyrochlore oxide may accommodate the well-defined two-in-two-out spin ice state with its tetrahedral unit. Low-energy excitation is argued to favor the highly concerned monopole state which attracts essential attention. However, such an excitation cannot be directly tracked and imaged using advanced characterizations, raising challenges to our understanding of the physics of monopoles. In this work, we propose an improved two-dimensional artificial spin ice structure on the Shastry–Sutherland lattice to restore the degeneracy of realistic pyrochlore systems. Such a structure avoids the deficiency of inequivalent nearest and next-nearest exchanges in the planar quadrate unit, which, however, is equivalent to the tetrahedral unit of realistic pyrochlore oxides. Therefore, this spin ice model restores state degeneracy that is lost in conventional planar artificial spin ice structures, representing an improved simulator of real spin ice systems. Our careful investigations of such improved structures reveal the rich physics of spin ice excitations, including the phase diagram, which allows different ordered phases and interesting critical phase transitions between spin ice phase I and phase II. Energy spectrum analysis suggests that restoration of state degeneracy substantially reduces monopole excitation energy, resulting in a striking monopole emergency at the critical point. Furthermore, the emergent spin dimer phase in this improved model allows high-density monopole excitations and exhibits high-correlated monopole fluid states. [ABSTRACT FROM AUTHOR]

In this study, the influence of ceramic shield characteristics, including thickness and geometry, on the transmission spectrum and electron density measurements of a ceramic shield cutoff probe (CSC) was investigated to measure high-density or process plasma. Through electromagnetic simulations and circuit modeling, we examined the measurement characteristics of the CSC based on different ceramic shield geometries. When the ceramic shield is sufficiently thin, it does not affect the CSC wave transmission characteristics. However, for a thick ceramic shield, a cutoff frequency shift of up to 3% toward the lower side can occur. This shift is attributed to the electrical properties of the ceramic material, which can function as a parasitic capacitor. In addition, when fabricating a CSC, depending on the shape of the ceramic shield or the method used to couple it with the CSC body, a cutoff frequency shift can occur toward the lower side. The simulation results were validated through experiments, revealing a cutoff frequency shift toward the lower side of up to 18.0% in the simulations and up to 11.6% in the experiments. The findings of this study could assist in high-density or processing plasma measurements using cutoff probes. [ABSTRACT FROM AUTHOR]

The gas-phase rotational spectrum from 8 to 750 GHz and the high-resolution infrared (IR) spectrum of pyridazine (o-C4H4N2) have been analyzed for the ground and four lowest-energy vibrationally excited states. A combined global fit of the rotational and IR data has been obtained using a sextic, centrifugally distorted-rotor Hamiltonian with Coriolis coupling between appropriate states. Coriolis coupling has been addressed in the two lowest-energy coupled dyads (ν16, ν13 and ν24, ν9). Utilizing the Coriolis coupling between the vibrational states of each dyad and the analysis of the IR spectrum for ν16 and ν9, we have determined precise band origins for each of these fundamental states: ν16 (B1) = 361.213 292 7 (17) cm−1, ν13 (A2) = 361.284 082 4 (17) cm−1, ν24 (B2) = 618.969 096 (26) cm−1, and ν9 (A1) = 664.723 378 4 (27) cm−1. Notably, the energy separation in the ν16-ν13 Coriolis-coupled dyad is one of the smallest spectroscopically measured energy separations between vibrational states: 2122.222 (72) MHz or 0.070 789 7 (24) cm−1. Despite ν13 being IR inactive and ν24 having an impractically low-intensity IR intensity, the band origins of all four vibrational states were measured, showcasing the power of combining the data provided by millimeter-wave and high-resolution IR spectra. Additionally, the spectra of pyridazine-dx isotopologues generated for a previous semi-experimental equilibrium structure (reSE) determination allowed us to analyze the two lowest-energy vibrational states of pyridazine for all nine pyridazine-dx isotopologues. Coriolis-coupling terms have been measured for analogous vibrational states across seven isotopologues, both enabling their comparison and providing a new benchmark for computational chemistry. [ABSTRACT FROM AUTHOR]

A high-resolution absorption spectrum of the S1–S0 transition of free-base phthalocyanine was observed and analyzed with improved reliability. The spectrum, with a partially resolved rotational structure, was obtained by using the buffer-gas cooling technique and a single-mode tunable laser. Our new analysis reveals that the S 1 ← S 0 0 0 0 band belongs to the a-type transition, where the electronic transition moment aligns parallel to the NH–HN direction, allowing the assignment of the S1 state to 1B3u. These results agree with a prior study using supersonic expansion and are well supported by theoretical calculations. Interestingly, the rotational constant B in the S1 state, which is often smaller than that in the ground state for typical molecules, was found to be slightly larger than that in the S01Ag state. This suggests a change in the character of π bonds with the electronic excitation. [ABSTRACT FROM AUTHOR]

It is important to understand the dynamics of red blood cells (RBCs) in blood flow. This requires the formulation of coarse-grained RBC models that reproduce the hydrodynamic properties of blood accurately. One of the models that successfully reproduces the rheology and morphology of blood has been proposed by Fedosov et al. [Comput. Methods Appl. Mech. Eng. 199, 1937–1948 (2010)]. The proposed RBC model contains several parameters whose values are determined by either various experiments or physical requirements. In this study, we developed a new method of determining parameter values precisely from the fluctuations of the RBC membrane. Specifically, we studied the relationship between the spectra of the fluctuations and model parameters. Characteristic peaks were observed in the spectra, whose peak frequencies were dependent on the parameter values. In addition, we investigated the spectra of the radius of gyration. We identified the peaks originating from the spring potential and the volume-conserving potential appearing in the spectra. These results lead to the precise experimental determination of the parameters used in the RBC model. [ABSTRACT FROM AUTHOR]

The canonical scenario of cross-flow vortex-induced vibration (VIV) of a circular cylinder in the turbulent regime, which has been studied by several physical experiments in the literature, is reexamined in this study through high-fidelity large-eddy simulations (LES) at a Reynolds number 104. The VIV response (including vibration amplitude and frequency) and hydrodynamic coefficients predicted by the present LES agree with the experimental results better than previous numerical attempts. In addition, several phenomena reported by previous experimental studies are confirmed numerically for the first time. After validating against the experiments, new VIV characteristics and physical mechanisms are explored with confidence. First, a collective analysis on the frequency spectra of the displacement, lift, and velocity signals provides a complete picture of the frequency response of the system. In contrast, the use of a single signal may miss certain aspects of the frequency response, so that caution should be exercised. Second, spanwise correlation of primary vortex shedding is examined, where relatively low correlations in the upper and lower branches are likely because the vortex shedding patterns involve complex vortex generation and interaction. Third, the effect of mass ratio (m*) of the cylinder on the VIV response is analyzed with a range of m* (=1.4–3.4) relevant to cylindrical structures used in offshore engineering (such as subsea pipelines). The variations in the amplitude response, frequency response, and hydrodynamic coefficients with m* and reduced velocity are examined in detail. The present results suggest that a lighter pipeline is more susceptible to the onset of VIV. [ABSTRACT FROM AUTHOR]

In this study, we consider the connection of the hydrodynamic force with vortex shedding behind a stationary sphere in an unbounded fluid at several Reynolds numbers, covering the range of critical transition from plane-symmetric to non-symmetric flow. A principal spectrum analysis (PSA) is employed/proposed to obtain the spectral representation (SR) modes for each time-varying force coefficient; this enables us to identify (i) one single characteristic frequency at R e = 300 , 350, and 380, i.e., the fast frequency f V S which represents the frequency of vortex shedding and (ii) two characteristic frequencies at R e = 390 , 400, and 420: one is the first fast frequency f 1 = f V S , representing the frequency of vortex shedding, and the other is the second fast frequency f 2 , representing the frequency of side oscillations of the vortex flow in the transverse flow direction. In the situations of the latter set of Reynolds numbers, the SR modes indicate that not only the strength but also the phase of shed vortex varies slightly at each successive vortex shedding, and most notably, we have identified rotation of the vorticity pattern in the near wake about the central axis. The PSA-SR mode analysis reveals that these three vortex activities all co-operate at the integer multiples of the greatest common-divisor of the two characteristic frequencies ( f 1 , f 2 ). In other words, the intricate subtlety of vortex shedding behind a stationary sphere can well be uncovered through the PSA-SR mode analysis for establishing the close connections between the force coefficients and the vorticity activities behind the sphere. The present work represents a sequel to our previous study: A spectral force representation and its physical implication for vortex shedding past a stationary or an oscillating circular cylinder at low Reynolds numbers [Lu et al., "A spectral force representation and its physical implication for vortex shedding past a stationary or an oscillating circular cylinder at low Reynolds number," Phys. Fluids 35(5), 053606 (2023)], where we initially proposed the PSA-SR analysis to establish the connections between the force coefficients and the vortex shedding of the circular cylinder under pre-, sub-, and normal synchronization. [ABSTRACT FROM AUTHOR]

This study explores the effects of bubble distribution parameters on the noise spectrum of bubble clusters through direct numerical simulations across volume fractions from 0.005% to 40%. Three types of bubble cluster distributions were analyzed: layered (uniformly sized bubbles with layered positioning), random (uniformly sized bubbles with random positioning), and lognormal (log-normally distributed bubble sizes with random positioning). Using the Ffowcs Williams–Hawkings (FW–H) method, we evaluated the sound pressure levels of the clusters. We found that the arrangement of bubble positions has little impact on the collapse times of bubble clusters. At volume fractions greater than 0.5%, bubble size also shows minimal effect on collapse times. However, when the volume fraction is less than 0.5%, the collapse times gradually approach the collapse time of the largest bubble in the cluster in a free field. Noise spectrum analyses showed that the arrangement of bubble positions significantly influences the noise spectra within the volume fraction range of 0.5%–25%, but has minimal impact outside this range. Importantly, the distribution of bubble sizes shows negligible effects on the noise spectrum, demonstrated by the nearly identical sound pressure level octave decay rates for random and lognormal clusters at the same volume fractions. This consistency can be mathematically described by the fitting formula: decay rate (dB/octave) = 18.192 × α − 0.047 −16.264. These findings enhance our understanding of the noise spectrum across varied bubble cluster distributions and provide new insights into the mechanisms of cavitation noise. [ABSTRACT FROM AUTHOR]

We investigated the effect of the sheath around the probe tips on the transmission spectrum of a cutoff probe using an electromagnetic simulation and a circuit model. Our results show that the width of the sheath can change the transmission spectrum, which can affect the absolute value of the electron density. In a real-world cutoff probe structure, this effect may become apparent in a low-density plasma or when a high bias voltage is applied to the plasma. The key factor is capacitance, which contains the sheath component. In the case of a low-density plasma, the change in the sheath capacitance of the sheath region contributes to the shift in the resonant frequency. For thick sheath widths, at least a 5% discrepancy can occur between the actual plasma frequency and the measurement owing to variations in the capacitance, particularly the sheath components surrounding the probe. We expect that this study will facilitate reduction in the measurement error and uncertainty in microwave cutoff probe measurements, particularly when applied to low-density plasma measurements. [ABSTRACT FROM AUTHOR]

To study the initiation and development of interfacial electrical damage in multi-layer dielectrics, an aging test of 3-layer polyimide films was conducted under pulsed voltage with a repetitive frequency of 500 Hz and a maximal amplitude of 30 kV. The variation in the damage morphology with the number of applied pulses was analyzed by a statistical method. The circuit current and partial discharge at different aging stages was measured, and the Fourier transform infrared spectrum analysis results of the aged and unaged sample regions were compared. The results demonstrate that the partial discharge in the dielectric interface gap, which is unavoidable in manufacturing, is the main cause of damage. It initiates from the interface and grows into the interior of the dielectric with the application of pulses. When there are no macroscopic defects on dielectric films, damage presents a punctiform morphology. The damage process can be divided into the following three stages: surface roughening damage, steady growth stage of damage points, and pre-breakdown stage. Differing from dielectrics without macroscopic defects, dielectrics with original void defects present transverse dendritic damage channels that initiate from the edge of the defect. [ABSTRACT FROM AUTHOR]

A flat-cutoff sensor installed on the chamber wall or chuck allows precise measurement of the plasma density in real time, even with a wafer placed on the sensor. However, a few studies have been conducted on the measurement characteristics in an environment where a wafer containing a metal layer is placed on a sensor. In this study, we investigated the effect of wafers containing metal layers on flat-cutoff sensor measurements using circuit models and experiments. The metal layer in the wafer shifts the cutoff frequency up to four times higher, and the degree of shift depends on the plasma density. The relationship between the shift in the cutoff frequency and plasma density can be interpreted as the ratio of the plasma inductance to that of the metal layer from the circuit model of the flat-cutoff sensor. The calculation results were verified experimentally using wafers containing Al and Ti metal layers. As a result, measurement was found to be possible even when a wafer containing a metal layer was placed on a flat-cutoff sensor, and these results can improve the measurement accuracy of the flat-cutoff sensor for the real-time plasma measurement. [ABSTRACT FROM AUTHOR]

Fluidized beds are favored for their high efficiency in material and heat exchange. However, a limited understanding of two-phase flow dynamics leads to the construction of larger equipment and makes precise control of fluidized beds challenging. Since it is challenging to eliminate the impact of signal noise in experiments, which arises from the inconsistency of particles and measurement methods, a square fluidized bed model has been established for numerical analysis of the chaotic characteristics of two-phase flow. The bubble distribution in the fluidized bed was observed more clearly, the bubble behavior was combined with the chaotic parameters, and the two flow states and the chaotic state were analyzed comprehensively. The results show that the bubbles present a regular arrangement parallel to the diagonal in the early stage of bubbling. At the same time, smooth reconstructed attractors are observed. The increase in fluidization wind speed will make the attractors rough until collapse. The bubbling bed experiences bifurcation into chaos as the fluidization wind speed increases, and we can see this process through the pressure signal. The system state cannot be distinguished by correlation dimension or K-entropy alone. Comprehensive consideration of a variety of chaotic features can be used as a method to identify two-phase flow chaotic states. The method used in this paper combines bubble behavior, pressure signal, power spectrum analysis, phase space reconstruction, correlation dimension, and Kolmogorov entropy to distinguish the state of the fluidized bed more accurately. [ABSTRACT FROM AUTHOR]

Recently, the rapid progress of deep learning techniques has brought unprecedented transformations and innovations across various fields. While neural network-based approaches can effectively encode data and detect underlying patterns of features, the diverse formats and compositions of data in different fields pose challenges in effectively utilizing these data, especially for certain research fields in the early stages of integrating deep learning. Therefore, it is crucial to find more efficient ways to utilize existing datasets. Here, we demonstrate that the predictive accuracy of the network can be improved dramatically by simply adding supplementary multi-frequency inputs to the existing dataset in the target spectrum predicting process. This design methodology paves the way for interdisciplinary research and applications at the interface of deep learning and other fields, such as photonics, composite material design, and biological medicine. [ABSTRACT FROM AUTHOR]

Exploring very-large-scale motions (VLSMs) in open channel flows (OCFs) is crucial for comprehensively understanding material transport and energy exchange. While previous studies focused on OCFs in ideal flumes with simple boundaries, this paper presents large eddy simulation (LES) results on the existence and scale characteristics of VLSMs in complex river morphologies with the Minjiang River in southwestern China as a case study. This research demonstrates that the OpenFOAM-based LES model is capable of accurately reconstructing the time-averaged flow field and providing instantaneous velocity data that capture VLSMs with sufficient resolution. Spectrum analysis of the streamwise fluctuating velocity shows that VLSMs are present in the straight segment of the river, with streamwise wavelengths approximately (16–22) times the water depth but are absent in the bend and confluence segments due to the suppression by secondary currents. This article validates the effectiveness of LES in examining the characteristics of VLSMs in natural rivers, thereby laying a good foundation for further studies on the impacts of such structures on sediment transport and pollutant dispersion. [ABSTRACT FROM AUTHOR]

The Mg-42Zn-7Y alloy, which contains an icosahedral quasicrystalline phase, was prepared using a conventional solidification process. The fracture toughness of this quasicrystalline phase in the Mg-42Zn-7Y alloy was nondestructively detected using in situ tensile and indentation techniques. The alloy exhibited a tensile strength of 99.17 MPa and an elongation of 3.9%. Microscopic observation and energy spectrum analysis confirmed the high-contrast lamellar structure as the quasicrystalline phase. Ultimately, under cyclic loading during indentation, the fracture toughness of the quasicrystalline phase was determined to be 35.08 MPa m0.5. The findings of the present study provided an effective basis for the determination of the fracture toughness of the quasicrystalline phase. [ABSTRACT FROM AUTHOR]

The nonlinear theory of radial correlation reflectometry (RCR) predicts that the cross correlation function of a signal follows a Gaussian distribution with a cutoff separation, where the correlation length is determined by both the turbulence amplitude and its radial correlation length. In contrast, phase spectrum analysis provides information solely on the turbulence amplitude. This work describes the possibility of applying both signal analysis methods and demonstrates that turbulence amplitude and radial correlation length can be simultaneously measured using RCR diagnostics in the nonlinear regime. [ABSTRACT FROM AUTHOR]

The characteristic frequency of a rub-impact fault is usually very complex and may contain higher harmonics and subharmonics. Due to the uncertainty of harmonic components and the complexity of signal-to-noise ratio (SNR) operation, the general scale transformation stochastic resonance (GSTSR) has certain limitations in the identification of rub-impact faults. To solve this problem, the paper starts with complexity and proposes a rub-impact fault identification method combining a swarm intelligence optimized algorithm (SIOA) with Hjorth parameters and GSTSR. The complexity of vibration signals will change greatly before and after rub-impact faults. The complexity parameter in Hjorth parameters can effectively embody the complexity of signals and is invulnerable to noise interference. Therefore, the complexity parameter in the Hjorth parameters is taken as the objective function of SIOA and combined with GSTSR. Vibration signals from cases are taken as input to adaptive stochastic resonant (ASR) systems, and the system parameters are adaptively and synchronously adjusted to realize the maximal resonant effect. Finally, the spectrum analysis of signals obtained from ASR is used to extract failure features and recognize faults in the rotor–stator rub-impact. The proposed method is verified by comparing it with other schemes under different SIOAs and different operating conditions. The result of the comparison shows that the complexity parameter of the Hjorth parameters can be taken as the objective function of SIOA to accurately identify the rub-impact fault. Meanwhile, the proposed method, compared with the method of taking SNR as an objective function, has a better effect on reducing time costs and strengthening fault characteristics. [ABSTRACT FROM AUTHOR]

A new technique for ex situ solid-state nuclear magnetic resonance imaging of polymeric films has been developed. This method uses the static magnetic field gradient generated by a water-cooled copper electromagnet. The imaging process involves scanning the sample in the plane of the film under a static magnetic field gradient. Two-dimensional (2D) 19F MRI measurements are attempted, where the fast Fourier transform (FFT) spectra of the second half of a Hahn echo peak is used for the depth (X-axis) direction, and the sample film is mechanically moved for the Y-axis, which is in-plane with respect to the film surface and normal to the inter-magnetic-pole line (Z-axis). The sample is a poly(tetrafluoroethylene) [PTFE] film with carved stripes on its surface. Furthermore, three-dimensional (3D) measurements of the film surface and thickness orientations were also performed for an analogous PTFE film. For 2D profiling on the film surface, 2D sample-moving was used. For depth profiling, FFT spectrum analysis was undertaken for each voxel situated at a specific (Y, Z) coordinate within the film. As a result, a 3D image of the sample and its corresponding geometry were obtained, although the scanning area was restricted to a part of the sample. Finally, numerical simulations of the spatial distribution of the static magnetic field were performed to confirm the validity of the present method. [ABSTRACT FROM AUTHOR]

A detailed consideration of the discrete mobility-spectrum analysis (DMSA) method and its application to transport studies in HgCdTe is given. First, a brief review of the methods of the analysis of field dependences of the Hall coefficient and conductivity in HgCdTe-based structures with a multi-carrier mobility spectrum is presented. The advantages and drawbacks of these methods, which include original mobility-spectrum analysis by Beck and Anderson, multi-carrier fitting and iterative approach by Dziuba and Górska, and the later developments of these techniques, are considered. The properties of the envelope of the mobility spectrum are analyzed, and the specifics of DMSA are presented. Analysis of some magnetic-field B dependences of conductivity tensor components σxx(B) and σxy(B) presented in the literature is performed with DMSA, and the results are compared to those obtained with other methods. [ABSTRACT FROM AUTHOR]

Computational analysis of difference spectra between two analogous systems is a challenging issue, as reliable estimation of a tiny difference spectrum requires an extraordinary precision of the two original spectra. We have developed an alternative new method to calculate the difference spectra under background-free conditions, which greatly improved the efficiency of computation. In this paper, we report further improvement by using efficient parallel implementation and the time correlation formula based on time derivative quantities. As a consequence, the present work achieved further remarkable acceleration in the calculations of difference infrared and Raman spectra in the order of magnitude and thereby allowed us by analyzing these difference spectra at a practical cost of computation. [ABSTRACT FROM AUTHOR]

The D5Π–X5Δ (0,0) band of vanadium hydride at 654 nm has been recorded by laser excitation spectroscopy and represents the first analyzed spectrum of VH in the gas phase. The molecules were generated using a hollow cathode discharge source, with laser-induced fluorescence detected via the D5Π–A5Π (0,0) transition. All five main (ΔΩ = ΔΛ) subbands were observed as well as several satellite ones, which together create a rather complex and overlapped spectrum covering the region 15 180–15 500 cm−1. The D5Π state displays the effects of three strong local perturbations, which are likely caused by interactions with high vibrational levels of the B5Σ− and c3Σ− states, identified in a previous multiconfigurational self-consistent field study by Koseki et al. [J. Phys. Chem. A 108, 4707 (2004)]. Molecular constants describing the X5Δ, A5Π, and D5Π states were determined in three separate least-squares fits using effective Hamiltonians written in a Hund's case (a) basis. The fine structure of the ground state is found to be consistent with its assignment as a σπ2δ, 5Δ electronic state. The fitted values of its first-order spin–orbit and rotational constants in the ground state are A = 36.5378 15 c m − 1 and B = 5.7579(13) cm−1, the latter of which yields a bond length of R 0 = 1.7212 2 Å. This experimental value is in good agreement with previous computational studies of the molecule and fits well within the overall trend of decreasing bond length across the series of 3d transition metal monohydrides. [ABSTRACT FROM AUTHOR]

There is a growing concern within the surface science community that the massive increase in the number of XPS articles over the last few decades is accompanied by a decrease in work quality including in many cases meaningless chemical bond assignment. Should this trend continue, it would have disastrous consequences for scientific research. While there are many factors responsible for this situation, the lack of insight of physical principles combined with seeming ease of XPS operation and insufficient training are certainly the major ones. To counter that, we offer a comprehensive tutorial written in the form of a step-by-step guide starting from experimental planning, through sample selection and handling, instrument setup, data acquisition, spectra analysis, and results presentation. Six application examples highlight the broad range of research questions that can be answered by XPS. The topic selection and the discussion level are intended to be accessible for novices yet challenging possible preconceptions of experienced practitioners. The analyses of thin film samples are chosen for model cases as this is from where the bulk of XPS reports presently emanate and also where the author's key expertise lies. At the same time, the majority of discussed topics is applicable to surface science in general and is, thus, of relevance for the analyses of any type of sample and material class. The tutorial contains ca. 160 original spectra and over 290 references for further reading. Particular attention is paid to the correct workflow, development of good research practices, and solid knowledge of factors that impact the quality and reliability of the obtained information. What matters in the end is that the conclusions from the analysis can be trusted. Our aspiration is that after reading this tutorial each practitioner will be able to perform error-free data analysis and draw meaningful insights from the rich well of XPS. [ABSTRACT FROM AUTHOR]

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a powerful surface analysis tool, which can simultaneously provide elemental, isotopic, and molecular information with part per million (ppm) sensitivity. However, each spectrum may be composed of hundreds of ion signals, which makes the spectra data complex. Principal component analysis (PCA) is a multivariate analysis technique that has been widely used to figure out the variances among samples in ToF-SIMS spectra data analysis and is showing great success in the explanation of complex ToF-SIMS spectra. So far, several software tools have been developed for PCA of ToF-SIMS spectra; however, none of them are freely available. Such a situation leads to some difficulties in extending applications of PCA to various research fields. More importantly, it has long been challenging for common researchers to understand PCA plots and extract chemical differences among samples. In this work, we developed a new and flexible software tool (named "advanced spectra pca toolbox") based on python for PCA of complex ToF-SIMS spectra along with an easy-to-read manual. It can generate data analysis reports automatically to explain chemical differences among samples, allowing less experienced researchers to easily understand tricky PCA results. Moreover, it is expandable and compatible with artificial intelligence/machine learning functions. Pure goethite and different lignin adsorbed goethite samples were used as a model system to demonstrate our new software tool, proving that our software tool can be readily used in complex spectra data processing. Our new software tool is open-source, convenient, flexible, and expandable. We expect this open-source tool will benefit the ToF-SIMS community. [ABSTRACT FROM AUTHOR]

To further improve the remaining useful life forecasting accuracy of fuel cells using classic deep learning models, a convolutional neural network combining bidirectional long and short-term memory networks (BiLSTM) and attention mechanism (AT) is optimized with the enhanced whale optimization algorithm (EWOA). Singular spectrum analysis preprocesses the attenuation data to eliminate noise and enhance its effective information; the CNN–BiLSTM model extracts spatiotemporal features and learns historical and future information; AT further explores the spatiotemporal correlation; and EWOA optimizes its hyperparameters to reduce human intervention error. Results demonstrate that, compared with long and short-term memory, CNN–LSTM, CNN–BiLSTM, CNN–BiLSTM–AT, and CNN–BiLSTM–AT optimized with other algorithms, the CNN–BiLSTM–AT model optimized with EWOA achieves lower root mean square error, mean absolute error, mean absolute percentage error, and relative errors of 0.1951%–0.2059%, 0.1267%–0.1538%, 0.0319%–0.0366%, and 0.026%–0.036%, respectively, with different training data. Importantly, the proposed model still maintains good prediction robustness with over 40% of the missing data. [ABSTRACT FROM AUTHOR]

The (sub-)millimeter wave spectrum of the non-rigid CH2OH radical is investigated both experimentally and theoretically. Ab initio calculations are carried out to quantitatively characterize its potential energy surface as a function of the two large amplitude ∠H1COH and ∠H2COH dihedral angles. It is shown that the radical displays a large amplitude torsional-like motion of its CH2 group with respect to the OH group. The rotation–torsion levels computed with the help of a 4D Hamiltonian accounting for this torsional-like motion and for the overall rotation exhibit a tunneling splitting, in agreement with recent experimental investigations, and a strong rotational dependence of this tunneling splitting on the rotational quantum number Ka due to the rotation–torsion Coriolis coupling. Based on an internal axis method approach, a fitting Hamiltonian accounting for tunneling effects and for the fine and hyperfine structure is built and applied to the fitting of the new (sub)-millimeter wave transitions measured in this work along with previously available high-resolution data. 778 frequencies and wavenumbers are reproduced with a unitless standard deviation of 0.79 using 27 parameters. The N = 0 tunneling splitting, which could not be determined unambiguously in the previous high-resolution investigations, is determined based on its rotational dependence. [ABSTRACT FROM AUTHOR]

In this paper, a novel methodology is presented for the construction of ab initio effective rotation–vibration spectroscopic models from potential energy and dipole moment surfaces. Non-empirical effective Hamiltonians are obtained via the block-diagonalization of selected variationally computed eigenvector matrices. For the first time, the derivation of an effective dipole moment is carried out in a systematic way. This general approach can be implemented quite easily in most of the variational computer codes and turns out to be a clear alternative to the rather involved Van Vleck perturbation method. Symmetry is exploited at all stages to translate first-principles calculations into a set of spectroscopic parameters to be further refined on experiment. We demonstrate on H2CO, PH3, CH4, C2H4, and SF6 that the proposed effective model can provide crucial information to spectroscopists within a very short time compared to empirical spectroscopic models. This approach brings a new insight into high-resolution spectrum analysis of polyatomic molecules and will be also of great help in the modeling of hot atmospheres where completeness is important. [ABSTRACT FROM AUTHOR]

A photothermal vortex interferometer (PTVI) is proposed to fill the gap of full-field measurement of the laser-induced nanoscale thermal lens dynamics of optical elements. The PTVI produces a multi-ring petal-like interferogram by the coaxial coherent superposition of the high-order conjugated Laguerre–Gaussian beams. The non-uniform optical path change (OPC) profile resulting from the thermal lens causes the petals of the interferogram at the different radii to shift by the different azimuths. To demodulate such an interferogram, an azimuthal complex spectra analysis is presented by using a camera with a pixelated multi-ring pattern written on its sensor to extract multiple azimuthal intensity profiles synchronously from the interferogram. Therefore, the OPC profile can be determined dynamically from the complex spectra of the azimuthal intensity profiles at the main frequency components. An analytical thermophysical model of the thermal lens is given, and the basic principle of the azimuthal complex spectra analysis is revealed. A proof-of-concept experiment is demonstrated using a N-BK7 glass sample heated by a pump laser. The results verified that the PTVI achieves the measurement accuracy of 47 pm with a standard deviation of 358 pm (3σ) and can be used for full-field measurement of the nanoscale OPC profile caused by the thermal lens dynamics. Due to the picometer-scale accuracy of the PTVI, the absorption coefficient and thermal diffusivity of the glass sample were determined to be A0 = 0.126 m−1 and D = 5.63 × 10−7 m2 s−1, respectively, which agree with the nominal ones of A0 = 0.129 m−1 and D = 5.17 × 10−7 m2 s−1. Although the PTVI is only suitable for measuring the rotationally symmetric OPC, it shows less computation burden and hardware complexity, and it is proved to be a highly sensitive and effective tool in studying optical, thermo-physical, and mechanical properties of optical elements. [ABSTRACT FROM AUTHOR]

The absorption spectra of thin films (CsCl)1–x(CuCl)x were studied at T = 90 K in the spectral range 2–6 eV. From the analysis of the spectra, the formation of CsCu2Cl3 and Cs2CuCl3 compounds in the CsCl–CuCl system was created. The Cs2CuCl3 compound is stable only in a vacuum; in air, it apparently decomposes into CsCu2Cl3 with a disordered crystal lattice and CsCl. The exciton spectrum of both compounds is interpreted on the basis of transitions in the Cu+ ion. The one-dimensional character of excitons in CsCu2Cl3 and the two-dimensional character in Cs2CuCl3 were established. [ABSTRACT FROM AUTHOR]

During the opening and closing process of the contact, it will undergo repeated arc ablation and wear. After each ablation and wear, the composition, performance, and shape of the contact surface constantly change, leading to cracks, slag drop, melting, evaporation, and other phenomena on the contact surface, ultimately causing the contact to fail, resulting in the switch not being able to open and close normally. In order to study the failure mechanism of arc contacts caused by arc erosion after breaking short-circuit current, a pair of arc contacts for the cumulative breaking short circuit current test was selected as the research object. The metallographic, microscopic morphology, and energy spectrum analysis of the arc contacts were conducted, and the analysis results were compared with the new arc contacts to reveal the evolution and development process of arc contacts from cumulative arc erosion to failure during breaking. [ABSTRACT FROM AUTHOR]

The atomization characteristics of impinging jets with high-frequency jet velocity perturbations is studied numerically based on the volume of fluid method. Three typical perturbation modes are considered to mimic the velocity discrepancies of jet flow in real engine conditions. Both the perturbation amplitude and frequency are investigated independently. Results show that the liquid sheet structure and atomization characteristics are significantly changed under the intrinsic perturbation frequency. The spectrum analysis is performed to reveal the specific phenomenon and explore the mechanism of different velocity perturbation modes. The analyses show that the atomization process is sensitive to perturbation frequency but its effectiveness diminishes significantly at excessively high frequencies. Additionally, when the frequency of velocity perturbation approaches the natural intrinsic frequency of sheet waves, resonance occurs within the liquid sheet for certain perturbation mode, leading to dramatic varies in breakup length and spray angle because the velocity superposition of the intrinsic and perturbed flow and its dynamics. [ABSTRACT FROM AUTHOR]

Perovskite La2Ti2O7 nanocrystalline powder was obtained through the shock synthesis method. In the study, La2O3 and TiO2 powders were mixed through ball milling and, subsequently, shocked by a flyer at a velocity of 3.2 km/s. After shock treatment, the sample was recovered and characterized via various techniques, such as x-ray diffraction, Raman, scanning electron microscope, transmission electron microscope, and ultraviolet-visible diffuse reflection spectrum analysis, to find the presence of La2Ti2O7 nanocrystalline powder with an average grain size of approximately 30 nm in the recovered samples with different yields. Moreover, the results further confirm that the high shock temperature and long ball milling treatment induce higher activation of precursors to improve the La2Ti2O7 content in the recovered samples. By adjusting the relative density of precursor and the ball milling period, pure La2Ti2O7 nanocrystalline powder was obtained. The formation mechanism of La2Ti2O7 was carefully illustrated. This study presents a new method to synthesize La2Ti2O7 nanocrystalline powder by detonation-driven flyer impact. [ABSTRACT FROM AUTHOR]

Mobility spectrum analysis (MSA) is a process of recovering the spectrum of carrier mobilities in an electronic material from a magnetic-field-dependent Hall measurement. This paper first presents a set of useful general properties of MSA that are true for all MSA methods. One such property is that Hall data can be classified as either "physical," with at least one spectrum of carrier mobilities that exactly fits the data, or "unphysical," where no mobility spectra exactly fit the data and the analysis must find approximate solutions. Almost all experimental Hall data collected at seven or more magnetic fields are slightly unphysical. The closest approximate solution for such unphysical data is always a set of discrete-carrier mobilities. A new method for multicarrier MSA is presented to display the likely properties of the discrete carriers as two-dimensional spectra vs both mobility and carrier density instead of one-dimensional spectra vs only mobility, as in previous methods. Measurement uncertainties are included as a fundamental part of the analysis so that the user can easily view the resultant uncertainty in the derived carrier properties. A separate method is also presented for reliably determining a smooth, high-entropy spectrum of carrier mobilities, which is constructed as the maximum-entropy linear combination of discrete-carrier solutions to the Hall data. An example using calculated Hall data corresponding to acoustic phonon scattering shows that the technique could potentially be used to measure the continuous mobility distributions that result from different scattering mechanisms. [ABSTRACT FROM AUTHOR]

Recent progress on (Si)GeSn optoelectronic devices holds great promise for photonic integration on Si substrates. In parallel to the development of bulk devices, (Si)GeSn-based quantum wells (QWs) have been investigated, aiming to improve device performance. While multiple QW structures are preferred for the device applications, a single quantum well (SQW) is more suitable for optical property studies. In this work, a comprehensive study of an SiGeSn/GeSn SQW was conducted. The calculated band diagram provided band alignment and energies of possible transitions. This SQW features a direct bandgap well with L–Γ valley energy separation of 50 meV, and barrier heights for both electron and hole are greater than 80 meV. Using two continuous-wave and two pulsed pumping lasers, the analysis of PL spectra allows for identifying different transitions and a better understanding of the SQW optical properties. This study could provide guidance for advancing the future QW design toward device applications. [ABSTRACT FROM AUTHOR]

A single-phase white light-emitting phosphor Ca3La3(BO3)5: Dy3+ (CLBD) was prepared via a solid-state reaction. The introduction of Dy3+ in Ca3La3(BO3)5 with a preferred location on La3+ was confirmed by x-ray diffraction and Rietveld structural refinement studies. The micrograph observed by scanning electron microscopy reveals an inhomogeneous and uneven dense morphology in the micrometer range. The optical spectra analysis shows that the CLBD can be efficiently excited by ultraviolet (UV) light and emitted intense white light due to the combination of blue 4F9/2 → 6H15/2 (∼485 nm) and yellow 4F9/2 → 6H13/2 (∼575 nm) emissions originated from 4f–4f transitions of Dy3+. The critical concentration is determined to be ∼12 mol. %, and the dipole–dipole (d–d) interaction is responsible for the quenching mechanism. In additional, the CLBD has high thermal stability. By incorporating the CLBD with a phosphor-capping method on AlInGaN LED, we obtain the white light that meets the spectral and efficiency requirements for high-efficacy solid-state white lighting lamps. The Commission Internationale de I'Eclairage chromaticity coordinates and color correlated temperature with optimal electroluminescence intensity are calculated to be ∼(0.338, 0.342) and 5950 K, respectively. All results indicate the CLBD could serve as a promising candidate for white UV-LEDs. [ABSTRACT FROM AUTHOR]

Over the last decades, photoreceptive proteins were extensively studied with biophysical methods to gain a fundamental understanding of their working mechanisms and further guide the development of optogenetic tools. Time-resolved infrared (IR) spectroscopy is one of the key methods to access their functional non-equilibrium processes with high temporal resolution but has the major drawback that experimental data are usually highly complex. Linking the spectral response to specific molecular events is a major obstacle. Here, we investigate a cyanobacteriochrome photoreceptor with a combined approach of transient absorption spectroscopy in the visible and IR spectral regions. We obtain kinetic information in both spectral regions by analysis with two different fitting methods: global multiexponential fitting and lifetime analysis. We investigate the ground state dynamics that follow photoexcitation in both directions of the bi-stable photocycle (Pr* and Pg*) in the nanosecond and microsecond time regimes. We find two ground state intermediates associated with the decay of Pr* and four with Pg* and report the macroscopic time constants of their interconversions. One of these processes is assigned to a structural change in the protein backbone. [ABSTRACT FROM AUTHOR]

In the growing field of high-field terahertz (THz) spectroscopy, many ultrafast research labs are equipped to perform single-pulse (one-dimensional) THz measurements. We describe a simple and versatile method to modify one-dimensional THz experimental setups to generate two variably delayed THz pulses. This method optimizes the use of pump power to create two high-field THz pulses. Adding only a beam splitter and delay stage, research groups can access the wealth of information only available through two-dimensional (2D) measurements. We also provide useful guidance to those new to some challenges of 2D THz spectroscopy. [ABSTRACT FROM AUTHOR]

Sum frequency generation (SFG) spectroscopy has been established as a powerful interface probe technique based on the electric dipole approximation, while possible signals of quadrupole and bulk origin have also been known for a long time. In this work, we developed a computational tool, namely, Qsac (quadrupole susceptibility automatic calculator), to evaluate the comprehensive contributions of the dipole/quadrupole and interface/bulk in the arbitrary vibrational bands of SFG spectra. The calculations of relevant susceptibility terms are performed on the basis of the theory of energy representation using quantum chemical calculation and molecular dynamics simulation, which allows for semi-quantitative comparison among these terms on the same footing. We applied the Qsac to the methyl C—H stretching bands of organic molecules and found a general trend that the weak asymmetric bands are more sensitive to the bulk contribution than the symmetric ones. The phases of interface and bulk terms tend to cancel in the asymmetric band, which results in the reduced band intensity in the SFG spectra. [ABSTRACT FROM AUTHOR]

A laser vaporization cluster source is coupled to the Fourier-transform ion cyclotron resonance mass spectrometer beamline of the free-electron laser for intracavity experiments. Gas phase metal ions and their oxides (VO2+, NbO2+, and TaO2+) are formed and spectroscopically characterized using IR multiple-photon dissociation spectroscopy via loss of atomic oxygen and overcoming fragmentation energies of 3 eV–6 eV. The signal is observed for all MO2+ fundamental modes: the symmetric and anti-symmetric ν1 and ν3 stretch modes in the 900 cm−1–1000 cm−1 range and the ν2 bending mode in the 300 cm−1–450 cm−1 range. A remarkable substructure is observed for the bending vibration, which is at least partly due to the rovibrational substructure. [ABSTRACT FROM AUTHOR]

Here, we discuss the application, advantages, and potential pitfalls of using transient UV/Vis (ultraviolet-visible) absorption spectroscopy to study photoelectrodes for water splitting. We revisit one of the most commonly studied water oxidation photoanodes (α-Fe2O3−x) to provide commentary and guidelines on experiment design and data analysis for transient absorption (TA) studies of photoelectrodes within a photoelectrochemical cell. We also assess the applicability of such in situ TA studies to understand photoelectrodes under operating conditions. A major limitation is that most, if not all, past in situ TA studies have been carried out using only pulsed light sources to generate carriers, with the electrode held in the dark at other times, which is shown to be a poor model for operating conditions. However, with a simple modification of existing TA experiments, a simple operando TA measurement is reported. [ABSTRACT FROM AUTHOR]

We report on the performance of Ar-filled hollow-core fibers (HCFs) capillary driven by long pulses (> --> 100 fs) of moderate energy (< 600 μ J) for coherent multidimensional spectroscopy in the visible range. The source is characterized by high overall transmission and excellent spatial mode. Broadening is achieved by self-phase modulation. Notably, the uncompressed visible output is shorter than the input pulse. This peculiar observation is explained by the structure of self-phase modulated pulses, coupled with spectral filtering. By virtue of its simplicity, low requirements, spectral stability, and the excellent properties of its spatial output, HCFs can provide an interesting alternative to achieve broadband visible pulses for broadband optical excitation and multidimensional spectroscopy applications. [ABSTRACT FROM AUTHOR]

We present a conspectus of recent joint spectroscopic and computational studies that provided novel insight into the photochemistry of hydrogen-bonded complexes of the heptazine (Hz) chromophore with hydroxylic substrate molecules (water and phenol). It was found that a functionalized derivative of Hz, tri-anisole-heptazine (TAHz), can photooxidize water and phenol in a homogeneous photochemical reaction. This allows the exploration of the basic mechanisms of the proton-coupled electron-transfer (PCET) process involved in the water photooxidation reaction in well-defined complexes of chemically tunable molecular chromophores with chemically tunable substrate molecules. The unique properties of the excited electronic states of the Hz molecule and derivatives thereof are highlighted. The potential energy landscape relevant for the PCET reaction has been characterized by judicious computational studies. These data provided the basis for the demonstration of rational laser control of PCET reactions in TAHz–phenol complexes by pump–push–probe spectroscopy, which sheds light on the branching mechanisms occurring by the interaction of nonreactive locally excited states of the chromophore with reactive intermolecular charge-transfer states. Extrapolating from these results, we propose a general scenario that unravels the complex photoinduced water-splitting reaction into simple sequential light-driven one-electron redox reactions followed by simple dark radical–radical recombination reactions. [ABSTRACT FROM AUTHOR]

Electronic spectra for the hypermetallic oxide MgOMg have been observed in the 21 100 cm−1–24 000 cm−1 spectral range using laser induced fluorescence and two-photon resonantly enhanced ionization techniques. Rotationally resolved data confirmed the prediction of a X ̃ 1 Σ g + ground state. The spectrum was highly congested due to the optical activity of a low-frequency bending mode and the presence of three isotopologues with significant natural abundances. Ab initio calculations predict a bent equilibrium structure for the à 1B2 upper state, consistent with the observation of a long progression of the bending vibration mode. However, the vibrational intervals were not reproduced by the theoretical calculations. In part, this discrepancy is attributed to strong vibronic coupling between multiple electronically excited states. Two-photon ionization measurements were used to determine an ionization energy of 6.5800(25) eV. [ABSTRACT FROM AUTHOR]

Quantum light is a key resource for promoting quantum technology. One such class of technology aims to improve the precision of optical measurements using engineered quantum states of light. In this study, we investigate transmission measurement of frequency-entangled broadband photon pairs generated via parametric down-conversion with a monochromatic laser. It is observed that state-to-state dynamics in the system under study are temporally resolved by adjusting the path difference between the entangled twin beams when the entanglement time is sufficiently short. The non-classical photon correlation enables time-resolved spectroscopy with monochromatic pumping. It is further demonstrated that the signal corresponds to the spectral information along anti-diagonal lines of, for example, two-dimensional Fourier-transformed photon-echo spectra. This correspondence inspires us to anticipate that more elaborately engineered photon states would broaden the availability of quantum light spectroscopy. [ABSTRACT FROM AUTHOR]

Development of noble metal nanostructure substrates that provide strong near-field enhancements enables applications of linear and nonlinear infrared (IR) spectroscopies to study minute sample quantities, such as nanometer thick films and molecular monolayers. Large near-field enhancements of the electric fields used for spectroscopic interrogation of molecules at the nanostructure surface result in enhancement of the spectroscopic signatures. This enhancement scales with the nonlinear order of the method, providing particularly large signal gains for third- and fifth-order IR methods, reaching 106 and 108 raw enhancement factors, not adjusted to the amount of interrogated sample. In this perspective, we overview the advances in the development of nano-arrays of antenna-like nanostructures for mid-IR measurements and illustrate their use in linear and especially nonlinear two-dimensional IR approaches. We discuss how studies of the interaction mechanisms between light, plasmonic antennas, and molecular excitations benefit from the nonlinear two-dimensional time-resolved methods, which involve high-order scaling of the signal with the excitation field, high sensitivity to signal localization, and coherence of the excitation over a broad bandwidth. On the other hand, we demonstrate how studies of molecular structure and ultrafast dynamics by these advanced spectroscopic methods benefit from surface enhancement of signals by plasmonic antennas. [ABSTRACT FROM AUTHOR]

We report on a simple method for the characterization of optical absorption in semiconductors at photon energies below the bandgap energy. Therefore, we perform spatially resolved and intensity dependent deflection spectroscopy to measure the local optical absorption. To separate the absorption mechanisms, we take advantage of different intensity scaling of these mechanisms and extract the material parameters by fitting intensity dependent absorption to a physical model. This model takes into account relevant optical absorption processes like linear absorption from defect states, two-photon absorption, and the Franz–Keldysh effect. The method is exemplarily carried out for GaAs, Si, and CdTe. The literature values of the two-photon absorption coefficient are reproduced and the strength of the Franz–Keldysh effect in CdTe is determined for the first time as C FK = [ 8.7 , ... , 16.9 ] × 10 13 m − 1 s − 1 / 2 . [ABSTRACT FROM AUTHOR]

The predissociation threshold of VO has been measured using resonant three-photon ionization (R3PI) spectroscopy. Given the high density of electronic states in the molecule, it is argued that the molecule dissociates rapidly as soon as the thermochemical bond dissociation energy (BDE) is exceeded, allowing the measured predissociation threshold to be assigned as the BDE. This is the first time a BDE has been measured using the R3PI method. The first photon is provided by an optical parametric oscillator (OPO) laser that promotes VO into a high-energy, discrete vibronic state. A tunable dye laser then excites the molecule further to a resonant state close to the dissociation limit where there is a quasi-continuum of states. A second photon from the same dye laser pulse ionizes the molecule, generating VO+ ions. The dye laser is then scanned to higher energies, and when the energy of one OPO photon plus one dye photon exceeds the BDE, the molecule dissociates before another dye photon can be absorbed to induce ionization. The combined photon energy at the sharp drop in the ion signal is assigned as the BDE. The experiment has been repeated using four different intermediate states, all yielding the same BDE, D0(VO) = 6.545(2) eV. Using thermochemical cycles, a revised value for the BDE of cationic VO is obtained, D0(V+–O) = 6.053(2) eV. The 0 K enthalpy of formation for VO(g) is also derived as Δ f H 0 K 0 VO (g) = 128.6(1.0) kJ mol−1. Previous spectroscopic and thermochemical studies of VO are reviewed. [ABSTRACT FROM AUTHOR]

A series of experiments are conducted for the study of time-dependent variations of major emission from the metastable excited He generated in various experimental conditions. Different Nd:YAG laser pulse widths and pulse energies, as well as purity of the He gas, are employed for studying quenching effects including the use of a Cu target in an experimental condition for spectrochemical analysis. It is found that in all cases investigated, the metastable excited He atom (He*) associated with the triplet He I 587.5 nm emission line has the unquestionable dominance over another triplet emission line of He I 388.8 nm and the singlet He I 667.8 nm emission. Further analysis of the present data combined with the results of previous studies suggested that the energy transfer between He atoms via the Penning-like collision-induced energy transfer process has so far remained less than appropriately addressed. It is strongly argued and demonstrated in this work that this underlying physical process is likely the moving force leading to the repeated He ionizations responsible for the self-propelled multiple amplification of the triplet He I 587.5 nm emission intensity particularly at the early stage of the shock wave formation. This study has convincingly demonstrated that the Penning-like collision-induced energy transfer process can also effectively take place between He* and the ablated atoms, implying its usefulness for spectrochemical laser-induced plasma spectroscopy analysis. [ABSTRACT FROM AUTHOR]

In this Tutorial, various methods of optical spectroscopy representing certain interest for magnetron discharge characterization are overviewed. The main principles, the implementation examples, and the selected results are given for each technique, accompanied by short discussions and suggestions for further reading. Both passive and active optical methods are covered, including optical absorption and laser-based techniques. The advantages and drawbacks of each diagnostic approach are critically analyzed. Special attention is devoted to the techniques extensively used by the authors in their own work, such as line ratio methods, absorption spectroscopy, interferometry, and laser-induced fluorescence. [ABSTRACT FROM AUTHOR]

In this article, we present high-pressure experimental investigations on EuNbO4, an interesting technologically important material, using synchrotron based x-ray powder diffraction, Raman spectroscopy, and europium photoluminescence measurements up to 39.2, 31.6, and 32.4 GPa, respectively. All three techniques show the stability of the ambient monoclinic phase until 20 GPa. Beyond that, a pressure-induced structural phase transition takes place with the coexistence of two phases over a wide pressure range. The structure of the high-pressure phase has been determined as orthorhombic (space group: Imma) with a volume discontinuity of nearly 9% at the transition indicating the nature of transition to be first order. The high-pressure phase remains stable up to ∼40 GPa. The equation of state data for both phases have been determined, and the modulus of incompressibility indicates that the high-pressure phase with bulk modulus as 246(29) GPa is less compressible compared to the low-pressure phase having bulk modulus as 138(4) GPa. The transition involves a change in the coordination polyhedron around europium, increasing the coordination number from 8 in the fergusonite to 12 in the orthorhombic phase, while the coordination around niobium remains 4 in both the phases. All the 18 expected Raman modes in the fergusonite structure have been observed, and their variation as a function of pressure has been reported. The mode Grüneisen parameters for the observed Raman frequencies for monoclinic and orthorhombic phases have been determined. Europium photoluminescence spectra show drastic changes near the transition pressure, which point toward changes in the local environment around the europium ion. [ABSTRACT FROM AUTHOR]

This study investigates element-specific atomic distances and strains in ferromagnetic (FM) nano-thin films deposited on a flexible substrate, which can be modulated by stretching the substrate. Extended x-ray absorption fine structure (EXAFS) spectroscopy was used for the experiments. Both in-plane tensile and out-of-plane compressive strains were investigated by applying %-order tensile strains to the substrate. The atomic distance changes induced by stretching the substrate were quantitatively discussed by considering the Poisson compression, crystalline orientations of the FM metals, and polarization in the EXAFS measurement. Consequently, the ratio of strain transfer from the flexible substrate to the FM layers was estimated to be about 30% and 60% in Co and Fe nano-thin films, respectively. The strain transfer in Co films with different Co or Pt underlayer thicknesses was also measured. The results are compared with the thickness dependence of the effective magnetoelastic coupling constant, which represents the magnitude of the inverse magnetostriction effect. Although the strain transfer partially contributes to the thickness dependence, the difference in the Co lattice constant is suggested to have a significant influence on the effective magnetoelastic coupling constant. [ABSTRACT FROM AUTHOR]