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We have applied positron annihilation spectroscopy to study the vacancy-type defects in β-Ga2O3 single crystals. The three different types of crystals were prepared by Czochralski and edge-defined film-fed growth and doped with Fe, Mg, and Sn for semi-insulating and n-type characteristics. The crystals were also subjected to 6-MeV proton irradiation for controlled introduction of mono-vacancy defects. Positron lifetime and the details of the anisotropy of the Doppler broadening signals were measured as a function of temperature, and the results were compared with the annihilation signals predicted by theoretical calculations. We find Ga vacancies in all three basic split Ga vacancy configurations to dominate the positron data in the as-grown crystals. In contrast, unrelaxed Ga vacancies are found as the main defect introduced by the irradiation. [ABSTRACT FROM AUTHOR]

We have applied positron annihilation spectroscopy to study the vacancy-type defects in β-Ga2O3 single crystals. The three different types of crystals were prepared by Czochralski and edge-defined film-fed growth and doped with Fe, Mg, and Sn for semi-insulating and n-type characteristics. The crystals were also subjected to 6-MeV proton irradiation for controlled introduction of mono-vacancy defects. Positron lifetime and the details of the anisotropy of the Doppler broadening signals were measured as a function of temperature, and the results were compared with the annihilation signals predicted by theoretical calculations. We find Ga vacancies in all three basic split Ga vacancy configurations to dominate the positron data in the as-grown crystals. In contrast, unrelaxed Ga vacancies are found as the main defect introduced by the irradiation. [ABSTRACT FROM AUTHOR]

Double Resonance is a powerful spectroscopic method that unambiguously assigns the rigorous quantum numbers of one state of a transition. However, there is often ambiguity as to the branch (ΔJ) of that transition. Spectroscopists have resolved this ambiguity by using the dependence of the double resonance intensity on the relative polarization directions of pump and probe radiation. However, published theoretical predictions for this ratio are based upon a weak (i.e., non-saturating) field approximation. This paper presents theoretical predictions for these intensity ratios for cases where the pump field is strongly saturating in the two limits of transitions dominated by homogeneous or of inhomogeneous broadening. Saturation reduces but does not eliminate the magnitude of the polarization effect (driving the intensity ratio closer to unity) even with strong pump saturation. For the case of an inhomogeneously broadened line, such as when Doppler broadened linewidth dominates over the power-broadened homogeneous line width, a large fraction of the low pump power polarization anisotropy remains. This paper reports predicted polarization ratios for both linear and circular pump and probe field polarizations. The present predictions are compared with experimental measurements on CH4 ground state → ν3 → 3ν3 transitions recently reported by de Oliveira et al.63 and these are in better agreement than with the weak field predictions. [ABSTRACT FROM AUTHOR]

In this article, we present a simulation study of the linear and nonlinear spectroscopy of dense atomic vapors. Motivated by recent experiments, we focus on double quantum spectroscopy, which directly probes dipole–dipole interactions. By explicitly including thermal velocity, we show that temperature has an important impact on the self-broadening mechanisms of the linear and nonlinear spectra. We also provide analytical expressions for the response functions in the short time limit using the two-body approximation, which shows that double quantum spectroscopy for atomic vapors directly probes the transition amplitude of the electronic excitation between two atoms. We also propose an expression for the double quantum spectrum that includes the effect of Doppler broadening, and we discuss the effect of density on the spectrum. We show that when Doppler broadening is negligible compared to self-broadening, the double quantum spectrum scales with the atomic density, while when Doppler broadening dominates, it scales as the square of the density. [ABSTRACT FROM AUTHOR]

A set of two newly designed, single-channel Czerny–Turner spectrometers has been deployed at the DIII-D tokamak for measurements of the motional Stark effect (MSE) split beam emission and the C6+ (CVI) carbon charge exchange recombination (CER) emission at high spectral (δλ = 0.13 nm) and temporal (1–5 kHz) resolution. High throughput optics (f/# = 2.8) allow for good signal-to-noise at high time resolution using fast EMCCD detectors. The MSE emission allows for spectral fitting of the magnitude and direction of the local B-field, while the carbon emission yields local ion temperature and toroidal rotation information. To reduce so-called Doppler broadening of the MSE emission, a new channel-specific variable lens-masking approach has been developed. Experimental data collected from the 2023 DIII-D experimental campaign demonstrate the signal quality and instrument fidelity for both diagnostic measurements. Moreover, initial CER data analysis shows a clear evolution of the toroidal rotation during edge localized modes. Initial progress on the advanced MSE model, including a new validated ray-trace model of the DIII-D collection optics, is shown via sensitivity analysis. [ABSTRACT FROM AUTHOR]

A 16 channel spectroscopy system has been installed on DIII-D to provide information about the energy distribution of the atomic neutrals using the Doppler shift and broadening of passive Balmer-α emission. The lines of sight are dominantly in the toroidal direction, with tangencies near the lowest point on closed magnetic flux surfaces moving from the lower divertor upward into the confined plasma. This allows the system to provide details of the neutrals as they undergo various atomic physics processes while traveling upward from the lower divertor. The spectrally resolved measurements provide several advantages that complement typical optical filter based measurements of hydrogenic spectral lines. These include more direct measurements of the neutrals that fuel deeper in the plasma and capturing neutral velocity distribution information via the Doppler broadened and shifted line. In addition, the spectral separation of higher energy "thermal" neutrals and bright cold emission from the scrape-off layer allows for a more straightforward calculation of the underlying neutral densities based on the emission because of the dependence of the thermal emission on confined plasma properties that are approximately flux functions and well measured. [ABSTRACT FROM AUTHOR]

The microstructure and chemical properties of the corona discharge process could provide an effective method for predicting the performance of high-voltage cable insulation materials. In this work, the depth profile of the microstructure and chemical characteristics of corona discharge-treated PE were extensively investigated using Doppler broadening of position annihilation spectroscopy accompanied with positron annihilation lifetime spectroscopy, attenuated total reflectance Fourier transform infrared spectra, Raman spectra and contact angle measurement. By increasing corona discharge duration, the oxygen-containing polar groups, including hydroxyl, carbonyl and ester groups, strongly contribute to the deterioration of hydrophobicity and the enhancement of hydrophilicity. And the mean free volume size, with a broadening distribution, decreases slightly. The line shape S parameter decreases because of the decrease in free volume elements and the appearance of oxygen-containing groups. Also, the thickness of the degradation layer, determined from the S parameter with positron injection depth, increases and diffuses into the PE matrix. A linear S-W plot within the degradation layer of different corona treatment duration samples indicates the defect type does not change. The S parameter decreases and the W parameter increases with an increasing corona duration. Using a slow positron beam, the nondestructive probe can be used to profile the microstructure and chemical environment across the corona discharge damage depth, which is beneficial for investigating the surface and interfacial insulation materials. [ABSTRACT FROM AUTHOR]

Hydrothermal treatments of soda–lime silicate glass cause a remarkable improvement in the resistance to flaw formation with an increase of the critical load to ≈1 kgf. This remarkable effect is achieved even if the reaction layer between the glass and water solution is well below 1 µm. Positron Doppler broadening spectroscopy (DBS) reveals that the hydrothermal treatment causes a drop in the free volume of the glass network near the surface connected with the diffusion of molecular water whose presence was further confirmed by Fourier transformed infrared (FTIR) spectroscopy and secondary ion mass spectrometry (SIMS). Based on FTIR and SIMS, we also argue that the hydrothermal ion exchange is a double‐step process: first H+ substitutes Na+ in the network, and following molecular water permeates the system. Moreover, we show that the presence of water in the network is fundamental in stabilizing the modified glass surface leading to toughening. Once molecular water is released, the network is quickly polymerized and becomes more brittle. Hydrothermal toughening is only a partially reversible process, once water is released it is not possible to reobtain the same properties with a second treatment. Finally, it is shown that air and tin side of the float glass perform differently as a result of different water diffusion kinetics related to dissimilarities in the network density. [ABSTRACT FROM AUTHOR]

Fast beam collinear laser spectroscopy is the established method to investigate nuclear ground state properties such as the spin, the electromagnetic moments, and the charge radius of exotic nuclei. These are extracted with high precision from atomic observables, i.e., the hyperfine splitting and the isotope shift, which become possible due to a large reduction of the Doppler broadening by compressing the velocity width of the ion beam through electrostatic acceleration. With the advancement of experimental methods and applied devices, e.g., to measure and stabilize the laser frequency, the acceleration potential became the dominant systematic uncertainty contribution. To overcome this, we present a custom-built high-voltage divider, which was developed and tested at the German metrology institute, and a feedback loop that enabled collinear laser spectroscopy to be performed at a 100-kHz level. Furthermore, we describe the impact of field penetration into the laser–ion interaction region. This affects the determined isotope shifts and hyperfine splittings if Doppler tuning is applied, i.e., the ion beam energy is altered instead of scanning the laser frequency. Using different laser frequencies that were referenced to a frequency comb, the field penetration was extracted laser spectroscopically. This allowed us to define an effective scanning potential to still apply the faster and easier Doppler tuning without introducing systematic deviations. [ABSTRACT FROM AUTHOR]

The temperature measurement of material inside of an object is one of the key technologies for control of dynamical processes. For this purpose, various techniques such as laser-based thermography and phase-contrast imaging thermography have been studied. However, it is, in principle, impossible to measure the temperature of an element inside of an object using these techniques. One of the possible solutions is measurements of Doppler brooding effect in neutron resonance absorption (NRA). Here we present a method to measure the temperature of an element or an isotope inside of an object using NRA with a single neutron pulse of approximately 100 ns width provided from a high-power laser. We demonstrate temperature measurements of a tantalum (Ta) metallic foil heated from the room temperature up to 617 K. Although the neutron energy resolution is fluctuated from shot to shot, we obtain the temperature dependence of resonance Doppler broadening using a reference of a silver (Ag) foil kept to the room temperature. A free gas model well reproduces the results. This method enables element(isotope)-sensitive thermometry to detect the instantaneous temperature rise in dynamical processes. Non-contact thermometry is one of the key technologies for modern science and industry. Here, authors demonstrated measurement of temperature of an element using neutron resonance spectroscopy with Doppler broadening with single intense short neutron pulse provided from high peak power. [ABSTRACT FROM AUTHOR]

The study investigates the effect of gamma radiation on defect formation in 20 nm titanium nitride (TiN) nanocrystals through positron annihilation lifetime (PALS) and Doppler broadening spectroscopy (DBS) studies. PALS studies were performed at atmospheric pressure, and DBS studies were performed under high vacuum conditions of 10−9 Torr. Gamma irradiation of the samples was performed in MRX-25 gamma device using 60Co isotope with 1.27 MeV energy at absorption doses of 50, 200, 900, and 3500 kGy. Two lifetime components were observed in the PALS results. Under the influence of gamma radiation, τ1 increases from 170 to 179 ps, and τ2 increases from 325 to 398 ps. As the radiation dose increases, the intensity corresponding to the short lifetime component I1 increases (from 75.6 to 81.2%), and I2 decreases (from 24.4 to 18.7%). PALS calculations were performed using the MICA package and a lifetime of 171 ps was determined for the 1Ti vacancy. With the help of Doppler broadening spectroscopy, information about the change and type of defects in the TiN nanocrystal along the volume was behavior of by studying S and W parameters. The results showed that the functionality of the material is optimal at gamma radiation doses not exceeding 3000 kGy. [ABSTRACT FROM AUTHOR]

We have applied the empirical Green's function (EGF) method to 53 pairs of earthquakes, with magnitudes ranging from M = 0.4 to M = 3.4, induced by gas production from the Groningen field in the Netherlands. For a subset of the events processed, we find that the relative source time functions obtained by the EGF deconvolution show clear indications of a horizontal component of rupture propagation. The earthquake monitoring network used has dense azimuthal coverage for nearly all events such that wavelet duration times can be picked as a function of source-station azimuth and inverted using the usual Doppler broadening model to estimate rupture propagation strike, distance, and velocity. Average slip velocities have also been estimated and found to be in agreement with typical published values. We have used synthetic data, from both a simple convolutional model of the seismogram and more sophisticated finite difference rupture simulations, to validate our data processing workflow and develop kinematic models which can explain the observed characteristics of the field data. Using a measure based on the L1-norm to discriminate results of differing quality, we find that the highest quality results show very good alignment of the rupture propagation with directions of the detailed fault map, obtained from the full-field 3D seismic data. The dip direction rupture extents were estimated from the horizontal rupture propagation distances and catalogue magnitudes showing that, for all but the largest magnitude event (the M = 3.4 event of 8th January 2018), the dip-direction extent is sufficiently small to be contained wholly within the reservoir. [ABSTRACT FROM AUTHOR]

In this work, the evolution of superparamagnetism (SPM) at room temperature is observed in the reactive magnetron sputter deposited amorphous Al-N-O alloy thin films after irradiation with oxygen ions (O−). Energy dispersive X-ray (EDX) analysis reveals the presence of notable Al-vacancy (V Al) in as-grown Al-N-O alloy thin film. X-ray photoelectron spectroscopy (XPS) confirms nitrogen trapping at V Al sites for thermodynamic stability, forming the Al(NO y) x phase. Upon the irradiation using O− at low fluence, i.e. 5 × 1013 ions/cm2, mainly V Al -O N complexes emerged. Here O N refers to nitrogen replaced by oxygen. Furthermore, an increase in oxygen fluence from 1 × 1015 to 2 × 1016 ions/cm2 yields the cross-over from V Al -O N complexes to mainly V Al , due to knocking off the trapped nitrogen atoms at V Al sites. From depth-resolved positron beam-based Doppler broadening measurements, the greater density of V Al sites is noticed in the film irradiated with the highest fluence of O− ion, i.e., 2 × 1016 ions/cm2. The correlation between the elevation of V Al sites with O− irradiation dose is in excellent agreement with the emergence of superparamagnetism (SPM) in the films. Hence, the emergence of SPM in the film after irradiation has been attributed to the creation of V Al sites, which leads to a localized magnetic moment. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive investigation of the electrochemical characteristics and structural properties of novel nanocomposites with varying compositions of (In 2 O 3) x /(Fe 2 O 3) 1-x , where x ranges from 1 to 0. These nanocomposites were synthesized using a versatile and cost-effective co-precipitation method. The crystallographic structure and morphology of the synthesized samples were thoroughly analyzed using Powder X-ray diffraction (PXRD) and Tunneling Electron Microscopy (TEM). Advanced analytical techniques were employed including Positron Annihilation Lifetime Spectroscopy (PALS) and Coincidence Doppler Broadening Spectroscopy (CDBS) to uncover critical insights into the structural and molecular properties of these nanocomposites. PALS analysis revealed valuable insights into the pore characteristics of the nanocomposites, while CDBS identified crucial molecular interactions within the materials. Electrochemical characterization of the nanocomposites is carried out using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical-impedance-spectroscopy (EIS) measurements. The (In 2 O 3) 0.3 /(Fe 2 O 3) 0.7 nanocomposite exhibits a remarkable specific capacitance of 945 F g-1 at 1 A g-1 and exceptional rate performance, retaining 93.6% of its specific capacitance at a six-fold higher current density. Moreover, this nanocomposite electrode demonstrates outstanding cyclic stability, maintaining 92.1% of its specific capacitance even after 3000 GCD cycles at 8 A g-1. These findings suggest that the novel composition and integrated electrochemical properties of the (In 2 O 3) 0.3 /(Fe 2 O 3) 0.7 nanocomposite hold great promise for enhancing the performance of next-generation electrochemical capacitors. This research contributes valuable insights into the design and development of advanced energy storage materials with applications in various high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

The maritime airborne corner reflector (ACR) is a radar reflector that can measure wind speed in an unknown sea area in real time over a long distance. To improve our understanding of how the ACR works, we investigated the Doppler characteristics of the ACR for the first time from a dynamic perspective. First, we constructed a radar echo signal model of the ACR. Then, we obtained the dynamic Doppler characteristics through pulse Doppler processing and discussed the special phenomenon of Doppler broadening. Finally, we proposed a rectangular window decomposition method to analyze the inner principle of the Doppler broadening phenomenon in more detail. In conclusion, this study provides valuable insights into the Doppler characterization of an ACR from a dynamic viewpoint, which contributes to enriching the basic theory of this equipment. [ABSTRACT FROM AUTHOR]

Minute examination of local lattice structures in matter affected by impurity doping is of special importance for the development of functional materials. In order to obtain microscopic information on spinel ferrites, in the present work, we introduced nonmagnetic In3+ ions in Fe3O4 and probed their site selectivity and the doping effect on the local lattice structures and bulk magnetism by means of 57Fe Mössbauer spectroscopy and positron annihilation spectroscopies. The Mössbauer parameters of the area intensity and isomer shift (IS) show that In3+ ions predominantly reside in the tetrahedral A site, especially at low doping level. With increasing concentration of In ions, however, they gradually occupy the octahedral B site replacing Fe3+ ions. Along with the site information, the IS values confirmed that the introduced In ions squeeze the B-site Fe ions at their nearest neighbors. Supporting results were obtained from positron annihilation lifetime spectroscopy; positron lifetimes become shorter with increasing In concentration, signifying that the oxygen ions are pressed by the introduced In ions resulting in lowering the volume of the adjacent lattice vacancies. The results of Doppler broadening spectroscopy also support the squeezing effect; the positrons in the vacancies adjacent to In ions are more likely to annihilate with the inner shell electrons of the surrounding oxygen ions as a result of a reduction in the vacancy volume. [ABSTRACT FROM AUTHOR]

Minute examination of local lattice structures in matter affected by impurity doping is of special importance for the development of functional materials. In order to obtain microscopic information on spinel ferrites, in the present work, we introduced nonmagnetic In3+ ions in Fe3O4 and probed their site selectivity and the doping effect on the local lattice structures and bulk magnetism by means of 57Fe Mössbauer spectroscopy and positron annihilation spectroscopies. The Mössbauer parameters of the area intensity and isomer shift (IS) show that In3+ ions predominantly reside in the tetrahedral A site, especially at low doping level. With increasing concentration of In ions, however, they gradually occupy the octahedral B site replacing Fe3+ ions. Along with the site information, the IS values confirmed that the introduced In ions squeeze the B-site Fe ions at their nearest neighbors. Supporting results were obtained from positron annihilation lifetime spectroscopy; positron lifetimes become shorter with increasing In concentration, signifying that the oxygen ions are pressed by the introduced In ions resulting in lowering the volume of the adjacent lattice vacancies. The results of Doppler broadening spectroscopy also support the squeezing effect; the positrons in the vacancies adjacent to In ions are more likely to annihilate with the inner shell electrons of the surrounding oxygen ions as a result of a reduction in the vacancy volume. [ABSTRACT FROM AUTHOR]

Electron beam powder bed fusion (E-PBF) is an attractive technology for the additive manufacturing of metal parts. However, process improvements require precise control of the energy transferred to the powder by the electron beam. Here, we used tunable diode laser absorption spectroscopy (TD-LAS) to measure the velocity distribution functions of titanium atoms evaporated during E-PBF. The narrow spectral ranges emitted by laser diodes allow for high-resolution absorption profiles of the evaporated atoms and thus accurate determinations of their Doppler broadening, density, and temperature during melting. The obtained vapor temperature reveals overheating at the surface of the melt pool relative to the low-pressure (0.1 Pa) boiling point of titanium, indicating that evaporation occurs under nonequilibrium conditions. We characterized the influence of the linear energy density on titanium evaporation and found it to be consistent with the saturation vapor pressure. Our characterization of the vapor properties provides reliable inputs for melt pool simulations. Furthermore, TD-LAS may be further exploited to prevent the evaporation of low-concentration alloy elements, which can induce defects in the printed part. [ABSTRACT FROM AUTHOR]

In the development of atomic physics, laser sources with Frequencies corresponding to atomic transition and high stability are essential. The Faraday laser is a special diode laser using the Faraday anomalous dispersion optical filter (FADOF) to realize frequency selection, so the output laser frequency is automatically limited to the atomic Doppler broadening. However, the frequency of a Faraday laser corresponds to the range around only one atomic hyperfine transition. Here, we realize a switchable Faraday laser with two isotopes laser frequencies corresponding to 85Rb 5 2 S 1 / 2 (F = 3) → 5 2 P 3 / 2 and 87Rb 5 2 S 1 / 2 (F = 2) → 5 2 P 3 / 2 transitions based on a single isotope 87Rb-FADOF. The laser has good robustness against the fluctuation of diode current and temperature, with wavelength fluctuating within 0.8 pm from 16 to 30 °C of diode temperature, and has a free-running linewidth of 18 kHz. We also lock the laser frequency to the two cycling transitions of 85Rb 5 2 S 1 / 2 (F = 3) → 5 2 P 3 / 2 (F ′ = 4) and 87Rb 5 2 S 1 / 2 (F = 2) → 5 2 P 3 / 2 (F ′ = 3) by the modulation transfer spectroscopy technique. The Allan deviation of the residual error signal is 3 × 10 − 14 / τ , and the frequency stability of the beat detection reaches 2.8 × 10 − 12 at 1 s integration time. This 780 nm switchable Faraday laser expands the application scenarios of Faraday lasers, which can be used in laser cooling atoms, optical frequency standards, and other quantum precision measurement fields. [ABSTRACT FROM AUTHOR]

A new x-ray imaging crystal spectrometer (XICS) has been installed, aligned, and used during experimental campaigns on the WEST tokamak. It has three interchangeable crystals for measuring the Ar XVII, Ar XVIII, and Fe XXV spectra, respectively. A patented rotating table holding the crystals is used to monitor the crystal facing the plasma remotely and without changing the position of the camera. Here, the focus is made on the Ar XVII spectrum, between 3.93 and 4.00 Å. The design of the diagnostic is presented, and a synthetic diagnostic, implemented with the Python library ToFu, is used to show the instrument's operational performance and limits. The instrument function exhibits the following two main features: a distortion for the Ar XVII spectrum, presumably due to the crystal manufacturing in two parts, and the measurement of three W spectral lines on the Ar XVI spectrum. Line of sight-integrated profiles of the electron and ion temperatures are thus extracted from the Ar XVII spectrum from two distinct spectral line ratios and from the Doppler broadening, respectively. The bremsstrahlung emission and the W line measurements are the two main limitations to compute the electron temperature. Tomographic inversions are also implemented with the library ToFu and used in order to obtain the local electron and ion temperature profiles, which are compared to other measurements from the WEST ECE (electron cyclotron emission) diagnostic. It is shown that both the XICS line-integrated and ECE Te measurements are in better agreement. Systematic differences are shown between the electron temperature profiles calculated from the two available line ratios. [ABSTRACT FROM AUTHOR]

Zr/Nb nanoscale multilayer coatings (NMCs) were studied after hydrogenation in a gaseous environment at 400 °C. The hydrogen distribution and content were determined by pressure and hydrogenation time. Increasing the pressure from 0.2 to 2 MPa resulted in different hydrogen distribution within the Zr/Nb NMCs, while the concentration remained constant at 0.0150 ± 0.0015 wt. %. The hydrogen concentration increased from 0.0165 ± 0.001 to 0.0370 ± 0.0015 wt. % when the hydrogenation time was extended from 1 to 7 h. The δ-ZrH hydride phase was formed in the Zr layers with Zr crystals reorienting towards the [100] direction. The Nb(110) diffraction reflex shifted towards smaller angles and the interplanar distance in the niobium layers increased, indicating significant lateral compressive stresses. Despite an increase in pressure, the nanohardness and Young's modulus of the Zr/Nb NMCs remained stable. Increasing the hydrogen concentration to 0.0370 ± 0.0015 wt. % resulted in a 40% increase in nanohardness. At this concentration, the relative values of the Doppler broadening variable energy positron annihilation spectroscopy (S/S0) increased above the initial level, indicating an increase in excess free volume due to hydrogen-induced defects and changes. However, the predominant positron capture center remained intact. The Zr/Nb NMCs with hydrogen content ranging from 0.0150 ± 0.0015 to 0.0180 ± 0.001 wt. % exhibited a decrease in the free volume probed by positrons, as demonstrated by the Doppler broadening variable energy positron annihilation spectroscopy. This was evidenced by opposite changes in S and W (S↓W↑). The microstructural changes are attributed to defect annihilation during hydrogen accumulation near interfaces with the formation of hydrogen–vacancy clusters and hydrides. [ABSTRACT FROM AUTHOR]

In a vapor cell, υ is the average velocity of the moving atoms. When υ ≪ c , the in-homogeneous broadening of the atomic spectral lines is important when taking into account thermal Doppler broadening. We also discover that the narrowing mechanism for inter-atomic with different components has more influence on the Doppler line-shape. Thus, the spectral line broadening of two-level and three-level multi-mer 8 5 R b atom is not only influenced by the in-homogeneous Doppler broadening, but also affected by the Dicke narrowing effect. The fluorescence spectrum affords a good possibility for a detailed study of Dicke narrowing effect and thermal Doppler broadening effect. We analyze the influence of multi-mer 8 5 R b atomic system component on resonance fluorescence spectrum (RFS). Based on the quantum regression theorem, we develop a method and derive a general analytical expression for the two-dimensional (2D) fluorescence correlation spectrum of three-level 8 5 R b atomic system. [ABSTRACT FROM AUTHOR]

Point defects in methylammonium lead iodide (MAPbI3) are believed to be the source of its room-temperature ferromagnetic behavior. The existence of room-temperature ferromagnetism observed through the hysteresis in the M-H (magnetization vs. magnetic field) curve proves that ferromagnetism is possible even at room temperature in the tetragonal phases of MAPbI3 system. Employing positron annihilation spectroscopy, the presence of a significant amount of point defects in the ball-mill ground MAPbI3 sample has been identified. Coincidence Doppler broadening spectroscopy identifies that the point defects are mostly iodine vacancy (V˙I) in MAPbI3. Experimental data supports the theoretical prediction of iodine vacancy (V˙I)-induced ferromagnetism in the cubic phase which exists at a little higher temperature than the room-temperature tetragonal phase for MAPbI3. Moreover, the ab-initio band structure calculation shows the n-/p-type semiconducting behavior due to the vacancy formation in MAPbI3. Ferromagnetism along with semiconducting properties makes it viable for spintronics applications. [ABSTRACT FROM AUTHOR]

We present a materials analysis method to enable in-situ Doppler broadening spectroscopy (DBS) of the 511 keV annihilation line in matter during tensile tests. This technique allows the correlation between the formation of lattice defects on an atomic scale and the macroscopic physical materials properties stress and strain. By implanting a monoenergetic positron beam into samples of AlMg3 (3.3535) and AlMgSi (3.3206) the onset of plastic deformation was clearly observed in the recorded annihilation spectra during the measurement of the corresponding stress–strain curves. The changes of the DBS spectra are attributed to positron annihilation in (open-volume) defects—predominantly vacancies elastically bound to dislocation lines—formed during plastic deformation. The elastic strain (Hook's region), however, does not lead to changes in DBS spectra. [ABSTRACT FROM AUTHOR]

We conduct a comprehensive spectro-temporal analysis of repeating fast radio bursts (FRBs) utilizing nine distinct sources, the largest sample to date. Our data set includes 175 sub-bursts and 31 multicomponent bursts from 11 data sets, with centre frequencies ranging from 149 to 7144  MHz and durations spanning from 73 µs to 13 ms. Our findings are consistent with the predictions of the triggered relativistic dynamical model (TRDM) of FRB emission. We affirm the predicted quadratic relationship between sub-burst slope and central frequency, as well as a linear dependence of the sub-burst bandwidth on central frequency that is consistent with mildly relativistic Doppler broadening of narrow-band emission. Most importantly, we confirm the sub-burst slope law, a predicted inverse relationship between sub-burst slope and duration, to hold consistently across different sources. Remarkably, we also discover that the drift rates of multicomponent bursts follow the same law as the sub-burst slopes, an unexplained result that warrants further investigation. These findings not only support the TRDM as a viable framework for explaining several aspects of FRB emission, but also provide new insights into the complex spectro-temporal properties of FRBs. [ABSTRACT FROM AUTHOR]

Coincidence Doppler broadening spectroscopy (CDBS), known for its exceptional precision, is extensively employed in examining the electronic states of polymers. In this study, polyvinyl chloride (PVC)–ethyl vinyl acetate (EVA) polymers blends were prepared using conventional techniques, following specific ratios (75:25, 50:50, and 25:75, respectively). Spectroscopic analysis reveals that the longitudinal component of linear momentum surpasses the momentum unit (i.e., 10−3 m0c) when considering the ratio curve associated with the participation of oxygen core electrons. When compared to non‐polymer samples, the PVA polymer and PVA–EVA polymer blend exhibit greater free volume voids in contrast to non‐polymer structural defects. Furthermore, the annihilation of ortho‐positronium with core electrons, likely EVA oxygen core electrons, contributes to the measured free volume voids. An increased annihilation of positrons or positroniums by oxygen in the CDBS spectrum leads to higher calculated W parameter values. Conversely, as the PVC content increases, the W parameter decreases, suggesting reduced ortho‐positronium annihilation and consequently, enhanced formation of para‐positronium in the overall annihilation process. In summary, this investigation demonstrates the utility of CDBS in elucidating the electronic states and free volume voids in PVC and EVA polymers. [ABSTRACT FROM AUTHOR]

The angular interrogation of sensitivity of the surface plasmon polariton waves (SPPs) is investigated at the interface under the effect of Doppler broadening dielectric medium and silver metal using prism geometry. A useful manipulation over the sensitivity of SPPs is obtained with Doppler broadening effect and parameters of the probe and control fields. The maximum sensitivity is investigated to 3000 deg/RIU with control field detuning, while the manimum sensitivity is reported to 300 deg/RIU with doppler width. The modified result of sensitivity of this manuscript shows potential applications in radiations guiding, photovoltaic devices, and solar cells devices. [ABSTRACT FROM AUTHOR]

Fe–Cr alloys are at the forefront for high radiation tolerant materials with long-standing validated performance. Yet, the detailed mechanism behind their high radiation resistance is in question and understanding the effect of varying Cr percentage is a grand challenge limiting further improvements. Here, we applied depth-resolved positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy to study the effect of Cr alloying on the formation and evolution of atomic size clusters induced by ion-irradiation in Fe. We also used atom probe tomography to investigate the possible presence of Cr clusters or α′ phase precipitates with high Cr composition. The study reveals that the well-known resistance to radiation in Fe–Cr alloys may arise from the stabilization of vacancy clusters around Cr atoms, which act as sinks for radiation-induced defects. This implies that Cr atoms do not provide a direct sink for interstitials; rather defect complexes that consist of Cr atoms and vacancies, in turn, act as sinks for irradiation-induced vacancies and interstitials. we also find that lower amounts of Cr create smaller defect clusters that act as efficient sinks for radiation damage, but larger quantities of Cr form a defect structure that is less homogenous and larger in size, resulting in less efficient damage recombination. No evidence of α′ was found before or after irradiation, which indicates that it does not contribute to the observed radiation tolerance. [ABSTRACT FROM AUTHOR]

Stark broadening parameters, line widths and shifts, for 15 N VI multiplets are calculated using semiclassical perturbation theory for temperatures from 50,000 K to 2,000,000 K, and perturber density of 10 16 cm − 3 . As perturbers have been taken electrons, protons and He III ions (alpha particles), which are of interest particularly for white dwarfs. Moreover, B III, B IV, B V and B VI ions have been taken as well, due to their significance for proton-boron fusion investigations. An example of the importance of Stark broadening in comparison with thermal Doppler broadening in atmospheres of spectral class DO white dwarfs is also presented. The obtained results are of interest particularly for white dwarf atmospheres modelling and analysis and synthesis of their spectra as well as for laser driven plasma in proton-boron fusion investigations. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of the structure of the Zr–1Nb alloy after modification by a high-current pulsed electron beam. The defective and phase structures were studied by the X-ray diffraction, positron lifetime spectroscopy, and Doppler broadening methods. The surface layer modification under electron-beam treatment was caused by the formation of a liquid phase and its subsequent congelation at the end of the pulse. It is shown that after the modification considerable changes of the annihilation parameters related to the change of the defect structure on the surface and in the volume of the material took place. Depending on the irradiation regime, the redistribution of positron annihilation probability between the two types of defects was observed. The pulsed electron beam irradiation of the Zr–1Nb alloy significantly changed the surface and structure of defects to a depth of up to 100 µm. It is shown that after the alloy modification by a pulsed electron beam, dislocation loops and vacancy-type defects prevailed. [ABSTRACT FROM AUTHOR]

Coherent microwave-to-optical conversion is crucial for transferring quantum information generated in the microwave domain to optical frequencies, where propagation losses can be minimized. Coherent, atom-based transducers have shown rapid progress in recent years. This paper reports an experimental demonstration of coherent microwave-to-optical conversion that maps a microwave signal to a large, tunable 550(30) MHz range of optical frequencies using room-temperature 87Rb atoms. The inhomogeneous Doppler broadening of the atomic vapor advantageously supports the tunability of an input microwave channel to any optical frequency channel within the Doppler width, along with the simultaneous conversion of a multi-channel input microwave field to corresponding optical channels. In addition, we demonstrate phase-correlated amplitude control of select channels, providing an analog to a frequency domain beam splitter across five orders of magnitude in frequency. With these capabilities, neutral atomic systems may also be effective quantum processors for quantum information encoded in frequency-bin qubits. Coherent microwave-to-optical conversion is crucial for networking physically separated quantum devices. This paper demonstrates coherent conversion of microwaves to a wide, tuneable optical frequency range using room-temperature Rb atoms, supporting frequency division multiplexing and coherent frequency channel control. [ABSTRACT FROM AUTHOR]

As part of efforts to develop coupled multiphysics experiments for the benchmark of modern multiphysics reactor simulators, a low-power and open-pool type of light water reactor at the Walthousen Reactor Critical Facility (RCF) was reconfigured with additional equipment, and its neutronic characteristics were fully surveyed. A water loop system was designed and installed to pass through the central region of the reactor core, making the central region overmoderated. The overmoderation would lead to a positive temperature reactivity feedback in the modified reactor configuration. This phenomenon is observed when the system temperature is between 10.69°C and 28.70°C. The inversion point of the isothermal reactivity coefficient is at 28.70°C ± 1.07°C. At this temperature, competition between the negative and positive thermal effects on reactivity compensate each other, and the isothermal reactivity coefficient becomes negative at temperatures higher than the inversion point. This paper presents the experimental determination of the isothermal reactivity and reactivity coefficient at different temperatures as well as the inversion point in the modified RCF reactor configuration. To obtain the best-quality results possible, special attention is given to the choice and adaptation of all the available methods for data postprocessing of experiment measurements. Neutron flux denoising is performed with multivariate wavelet transforms and principal component analysis. The Inverse Kinetics Method is applied to derive reactivity from the neutron flux measurements. To provide accurate and high-fidelity experiment benchmark data for modern code validation, in-depth experimental uncertainty quantification is developed. The results of the experiments show the mixed effects of system temperature on reactor reactivity due to the combined effects of Doppler broadening in the fuel, S(α,β) thermal scattering physics, and change in water density and can be used to validate previously developed cross-section interpolation models in the low-temperature range and positive isothermal reactivity coefficient conditions. [ABSTRACT FROM AUTHOR]

We infer the ultrahigh energy neutrino source by using the Glashow resonance candidate event recently identified by the IceCube Observatory. For the calculation of the cross section for the Glashow resonance, we incorporate both the atomic Doppler broadening effect and initial state radiation ν ¯ e e − → W − γ , which correct the original cross section considerably. Using available experimental information, we have set a generic constraint on the ν ¯ e fraction of astrophysical neutrinos, which excludes the μ-damped pγ source around 2σ confidence level under the assumption that neutrino production is dominated by the ∆-resonance. While a weak preference has been found for the pp source, next-generation measurements will be able to distinguish between ideal pp and pγ sources with a high significance assuming an optimistic single power-law neutrino spectrum. The inclusion of multi-pion production at very high energies for the neutrino source can weaken the discrimination power. In this case additional multimessenger information is needed to distinguish between pp and pγ sources. [ABSTRACT FROM AUTHOR]

Organic pollutants in water remain a hazard to the ecosystem, emphasizing the ongoing concern. Therefore, this study focused on the nano-sized spinel ferrite as a photocatalyst for dye degradation and probing how ferrite microstructure influences the photo-degradation efficiency. The NiFe2O4 and ZnFe2O4 nanoparticles (NPs) were synthesized using the co-precipitation and sol–gel methods, respectively. The effects of microstructure changes of pristine and annealed (450, 600, and 800 °C) ferrites were systematically examined using the positron annihilation lifetime (PAL) and Doppler broadening (DB) techniques. Rigorous analysis, featuring X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM), confirmed the cubic spinel nanostructure for the synthesized ferrite samples as a major phase. The optical properties of the prepared ferrite NPs were studied using the UV–Vis spectroscopy. Particle size ranged from 5.0 to 34.7 nm for NiFe2O4 and from 11.8 to 50.4 nm for ZnFe2O4. UV–Vis spectra unveiled bandgap energy ranges of 3.76–4.34 and 4.31–4.60 eV for Ni and Zn ferrites, respectively. The photo-degradation efficiency of methylene blue dye catalyzed by the prepared Ni and Zn ferrite NPs was investigated. Comparing PAL and DB parameters revealed notable differences, attributed to distinct crystallinity arising from varied synthesis methods. Remarkably, the highest photo-degradation efficiency was observed in the annealed NiFe2O4 at 800 °C and pristine ZnFe2O4 samples, surpassing others. This achievement was attributed to factors such as enhanced ordered crystallinity, increased vibrational modes, optimal particle size, fitting optical properties, and favorable defect characteristics. This study's novelty lies in highlighting the pivotal role of microstructure in governing ferrite NPs photocatalyst performance. We underscore the significance of the defect reduction, regardless of its type, size or concentration, to substantially enhance the photo-degradation efficiency. [ABSTRACT FROM AUTHOR]

The behavior of multilevel atomic ensembles (e.g., alkali-metal atoms) can be influenced significantly by the intensity of a driving field (or controlling/coupling field). The phase coherence between two transition pathways driven by a probe light and a driving field can lead to the effect known as electromagnetically induced transparency (EIT). In EIT, the probe light can pass through a three-level alkali-metal atomic vapor without absorption or reflection when two coherent resonances (transition pathways driven by the driving and probe fields) are present and the linewidths of the transparency windows are sufficiently narrow. The optical characteristics of atomic systems can also be affected by the Doppler broadening of the absorption profile in a spectroscope. Our analysis indicates that both broadenings (related to the transitions excited by the driving and probe fields) can be expanded, leading to an increase in the transmittance and reflectance broadenings when a coupling field with adaptive strength is applied; the corresponding temperature would, thus, be implemented and readable. We show that the most suitable preparation for temperature sensing via an EIT vapor is to provide 80 times the spontaneous decay rate (SDR) of the excited atomic levels. This configuration results in reflectance and transmittance values that range between zero and one and cover a temperature range of 0 K to 600 K. As an example, we demonstrate the integration of specialized coating technologies with EIT ensembles for temperature sensing in the range of dozens of kelvins at and above room temperature. A key advantage of this temperature-sensing system is its ability to use adaptive resonant visible light as the probe field. This novel approach may find applications in providing unprecedented levels of precision and control in temperature sensing for coating processes and in the design of other photonic or optical devices. It can also be used to determine the temperature-dependent behavior of the specific heat of alkali-metal solids and gases (including the latent heats of vaporization or sublimation of alkali-metal solids) through the reflection and transmission spectra of the vaporized EIT atomic vapors. [ABSTRACT FROM AUTHOR]

Tungsten has been considered as a potential candidate material for the application of plasma-facing components in magnetic confinement fusion reactors. Fusion neutrons introduce severe displacement damage into the first-wall materials along with a high amount of helium which is detrimental to the desirable material properties. Ion beam implantation combined with positron annihilation spectroscopy is a well-adopted method to investigate the irradiation damage in materials without any induced radioactivity. In this study, two separate tungsten samples were individually irradiated with 9.1 MeV Au5+ ions to a dose of 2.5 × 1014 ions/cm2 and 130 keV He ions to a dose of 1 × 1016 ions/cm2 with the intention to investigate the evolution of vacancy-type defects in the absence and presence of helium. The irradiated samples were subjected to isochronal annealing and characterized using positron annihilation Doppler broadening spectroscopy. The evolution of vacancy-type defects during different stages of annealing was investigated using defect-sensitive positron S-parameter. An increase in S-parameter due to the presence of vacancy-type defects was observed upon irradiation in both samples. The S-parameter variations with respect to the temperature showed different stages of vacancy annealing corresponding to stage III from 473 K to 673 K where the migration and clustering of mono-vacancies occurs, stage IV from 673 K to 973 K due to the growth of nano-voids and stage V from 973 K to 1273 K due to the dissociation of nano-voids. Complete recovery of irradiation-induced defects occurred in both samples at 1273 K. Both the samples showed similar vacancy annealing stages and no signature on the formation and growth of He-vacancy clusters or He bubbles was observed in the present study.

The present review is dedicated to the problem of an array of transitions between highly-excited atomic levels. Hydrogen atoms and hydrogen-like ions in plasmas are considered here. The presented methods focus on calculation of spectral line shapes. Fast and simple methods of universal ionic profile calculation for the H n α ( Δ n = 1 ) and H n β ( Δ n = 2 ) spectral lines are demonstrated. The universal dipole matrix elements formulas for the H n α and H n β transitions are presented. A fast method for spectral line shape calculations in the presence of an external magnetic field using the formulas for universal dipole matrix elements is proposed. This approach accounts for the Doppler and Stark–Zeeman broadening mechanisms. Ion dynamics effects are treated via the frequency fluctuation model. The accuracy of the presented model is discussed. A comparison of this approach with experimental data and the results of molecular dynamics simulation is demonstrated. The kinetics equation for the populations of highly-excited ionic states is solved in the parabolic representation. The population source associated with dielectronic recombination is considered. [ABSTRACT FROM AUTHOR]

The equilibrium FeNi alloy prefers face centered cubic (fcc) phase whereas the formation of metastable phases through certain low‐temperature synthesis methods is obscure. FeNi alloy exhibiting nonequilibrium body centered cubic (bcc) structure beyond 5 at% Ni is obtained through chemical reduction at 453 K with noticeable lattice shrinkage. Positron lifetime analysis and Doppler broadening spectroscopy are employed to probe the correlation between defects and phase stability. The mean lifetime of the chemically synthesized alloys is larger than 300 ps, implying an average of 7‐vacancy cluster. The modified two‐state trapping model reveals defect concentration in the range of 1022 m−3$\left(10\right)^{22} \left(\text{ m}\right)^{- 3}$, on par with irradiated alloys. Significant deviation in the high‐momentum component between the bulk and chemically synthesized samples is correlated to the changes in 3d electrons. The Fe and FeNi alloy uncover significant contraction in d‐band of Fe which facilitates bcc phase stabilization above 5 at% Ni through cluster vacancy formation. [ABSTRACT FROM AUTHOR]

The monitoring of the alpha irradiation effect on the microstructural deformation of CR39 via the variation of free volumes has been studied. CR39 samples have been irradiated with alpha particles at fluencies Φ of 2.6×108, 5.27×108, 7.91×108, 1.3×109, 1.84×109, and 3.6×109 α/cm². The samples have been investigated with positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy. The analysis of positron annihilation spectra has shown a variation of the ortho-positronium component τ3 and the parameters S and W as a function of the fluence Φ. This variation is related to a change in the size and number of free volumes, which is created via the evolution of chemical chains. From the values of τ3, the free volume radius has been estimated using the Tao–Eldrup model. Moreover, theoretical calculation of the radial dose distribution has been also performed using the Waligorski formulation to get the track core radius. After an etching of 5 min, the positron annihilation spectroscopy technique was again used to investigate the microstructural changes in etched samples subjected to alpha radiation. A clear variation of τ3, S and W parameters, and free volume radius has been noted when compared to the non-etched samples. [ABSTRACT FROM AUTHOR]

Alkali metal ion (Li+ and Na+)-doped CuO nanocrystallites were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), positron annihilation lifetime (PAL), and Doppler broadening annihilation radiation (DBAR) spectroscopy methods. A comparative analysis of XRD, TEM, average lifetime, and electron momentum variation is presented based on defect formation and curing. DBAR studies divulge the positron trapping sites as Cu vacancies and vacancy complex clusters in undoped CuO. The study also reveals lattice defect and migration of point defect in the doped CuO lattice. The positron lifetimes of undoped CuO show extended point defects, VCu–VO vacancy complexes, and voids. These defects are reduced to Cu interstitial (Cui) type point defects upon annealing. The lifetime confirms the VCu recovery and cluster vacancies for annealed Li- and Na-doped CuO. Higher Li concentrations showed a significant point defect of isolated oxygen vacancies as well as Li interstitials. Antisite and oxygen interstitial-type defects are prominent for all the Na concentrations. [ABSTRACT FROM AUTHOR]

The Full Law Analysis Scattering System Hub (FLASSH) is a modern, advanced code that evaluates the thermal scattering law (TSL) along with accompanying cross sections. FLASSH features generalized methods that accommodate any material structure. Historical approximations including incoherent and cubic approximations have been removed. Instead, the latest release of FLASSH features advanced physics options including distinct effect corrections (one-phonon contributions) and noncubic formulations. Noncubic elastic and inelastic contributions are necessary to accurately evaluate one-phonon contributions. Both noncubic and one-phonon calculations require high-density sampling of the various scattering directions. Optimization and parallelization of these routines were therefore necessary to produce results in a reasonable computational time frame. With these notable improvements to the generalized TSL, FLASSH 1.0 can meet benchmark requirements by permitting realistic comparisons with experiments for both TSLs and the resulting integrated cross sections. Within FLASSH, these high-fidelity TSLs can be applied also to the resonance region to evaluate accurate, material structure-dependent Doppler broadening that captures the observed experimental behavior. Additional features including a graphical user interface (GUI), plotting diagnostics, and formatted output options including ACE files allow users to complete a TSL evaluation with minimal input and maximum flexibility. The user GUI creates input files for FLASSH, reducing user error and also providing built-in error checks. Autofill options and suggested input values help make TSL evaluation accessible to novice users. The FLASSH code is compiled to run on both Windows and Linux platforms with automatic parallelization. [ABSTRACT FROM AUTHOR]

The Doppler coefficient represents the primary source of passive and instantaneous negative reactivity feedback to limit peak power excursion during reactivity-initiated accidents as well as a nonnegligible negative reactivity source that changes between cold zero-power and hot zero-power conditions. Furthermore, the mechanism behind the Doppler coefficient may also contribute to an increase in the buildup of Pu under normal operating conditions. As such, its treatment is critical in the design and evaluation of the safety and control of nuclear systems. This paper provides a brief overview of the physical source of the Doppler effect through resonance broadening from first principles as well as an exploration of some recent developments in the treatment of elastic scattering in the Monte Carlo codes Tripoli4® and MCNP. This exploration results in a detailed look at the effect different elastic scattering kernels have on the radiative capture, fission, and elastic scattering rates as they directly tie into the calculation of the Doppler coefficient via the six-factor formula. Also provided is some insight into the propagation of the a priori uncertainty of 238U resonance parameters. This work is performed pursuant to the development of a new experimental program to measure the Doppler coefficient in a zero-power reactor both more accurately and to higher temperatures (1500°C to 2000°C) than has been done in the past at the MINERVE facility at Cadarache. [ABSTRACT FROM AUTHOR]

Data on microporosity (micropore size distribution) in the range from several angstroms to several nanometers, obtained by measuring the positron annihilation lifetime (PALS method) and by measuring CO2 sorption (low-temperature gas sorption, LTGS) are collated for a number of polymers with amorphous (polyetherimides, PEI) and semicrystalline (polyphenylene oxides, PPO) structures. The microporosity estimates based on the positron annihilation and CO2 sorption data are compared with published data obtained both experimentally and by the group contribution method for the permeability of these materials. The discrepancies found and their possible causes are discussed. [ABSTRACT FROM AUTHOR]

The maritime airborne corner reflector (ACR) is a radar reflector that can measure wind speed in an unknown sea area in real time over a long distance. To improve our understanding of how the ACR works, we investigated the Doppler characteristics of the ACR for the first time from a dynamic perspective. First, we constructed a radar echo signal model of the ACR. Then, we obtained the dynamic Doppler characteristics through pulse Doppler processing and discussed the special phenomenon of Doppler broadening. Finally, we proposed a rectangular window decomposition method to analyze the inner principle of the Doppler broadening phenomenon in more detail. In conclusion, this study provides valuable insights into the Doppler characterization of an ACR from a dynamic viewpoint, which contributes to enriching the basic theory of this equipment.