Search

The spectral addressing of many individual rare‐earth dopants in optical resonators offers great potential for realizing distributed quantum information processors. To this end, it is required to understand and control the spectral properties of the emitters in micron‐scale devices. Here, erbium emitters are investigated in a Fabry–Perot resonator that contains a 10 µm thin membrane of crystalline yttrium orthosilicate that is co‐doped with europium. The co‐doping allows for tailoring the inhomogeneous distribution of the emitter frequency. With this approach, more than 360 spectrally resolved emitters are observed with Purcell factors exceeding 35, each of which constitutes an individually addressable qubit within the micron‐scale resonator. In addition to this spectral multiplexing, the optical coherence is preserved up to 0.62(3) ms under dynamical decoupling. Without decoupling, the coherence still reaches the lifetime limit for the emitters with the strongest Purcell enhancement that leads up to a 110‐fold lifetime reduction, down to 0.104(9) ms. Future work may combine this with long‐lived nuclear spin memories, which makes the investigated co‐doped membranes a promising platform for quantum repeaters and distributed quantum computers. [ABSTRACT FROM AUTHOR]

PurposeThis study aimed to characterize blood oxygen level-dependent (BOLD) effects in proton magnetic resonance (1H-MR) spectra obtained during optogenetic activation of the rat forelimb cortex to correct and estimate the accurate changes in metabolite concentration.MethodsFor a more comprehensive understanding of BOLD effects detected with functional magnetic resonance spectroscopy (fMRS) and to optimize the correction method, a 1 Hz line-narrowing effect was simulated. Then, proton functional magnetic resonance spectroscopy (1H-fMRS) data acquired using stimulated echo acquisition mode (STEAM) at 9.4T in rats (n = 8) upon optogenetic stimulation of the primary somatosensory cortex were utilized. The data were analyzed using MATLAB routines and LCModel. Uncorrected and corrected 1H-MR spectra from the simulated and in vivo data were quantified and compared. BOLD-corrected difference spectra were also calculated and analyzed. Additionally, the effects of stimulated and non-stimulated water on the quantification of metabolite concentration swere investigated.ResultsSignificant mean increases in water and N-acetylaspartate (NAA) peak heights (+1.1% and +4.5%, respectively) were found to be accompanied by decreased linewidths (−0.5 Hz and −2.8%) upon optogenetic stimulation. These estimates were used for further defining an accurate line-broadening (lb) factor. The usage of a non-data-driven lb introduced false-positive errors in the metabolite concentration change estimates, thereby altering the specificity of the findings. The water and metabolite BOLD contributions were separated using different water scalings within LCModel.ConclusionThe linewidth-matching procedure using a precise lb factor remains the most effective approach for accurately quantifying small (±0.3 μmol/g) metabolic changes in 1H-fMRS studies. A simple and preliminary compartmentation of BOLD effects was proposed, but it will require validation.

This study presents a straightforward solution to the challenge of elucidating the structures of nitrogen containing compounds undergoing isomerization. When spectral line broadening occurs related to isomerization, be it prototropic tautomerism or bond rotations, this poses a significant obstacle to structural elucidation. By adding acids, we demonstrate a simple approach to overcome this issue and effectively sharpen NMR signals for acid stable prototropic tautomers as well as the conformational isomers containing a morpholine or piperazine ring. [ABSTRACT FROM AUTHOR]

By examining the X-ray powder diffraction data, the microstructure of the BaTiO3 ceramic modified by alkaline earth (AE) metals was characterized. Following profile fitting, the X-ray powder diffraction data of the powder mixtures were analyzed to estimate and evaluate the structural changes of the single-phase AE-modified BaTiO3. Each compound, as well as several polymorphic versions of the same compound, had a unique diffraction pattern, which was a coded representation of the crystal structure. The sole requirement for deciphering this data was the generation of exact data in order to enable phase identification, measurements of lattice parameters, atomic positions, etc. This work compares the various structural characteristics of void species nanostructure using X-ray diffraction with respect to the first sharp diffraction peak (FSDP) of different samples. Various parameters were computed using general expression and a comparison was presented in this paper. [ABSTRACT FROM AUTHOR]

The cations of an ordered omphacite from the Tauern window were gradually disordered in piston cylinder experiments at temperatures between 850 and 1150 °C. The samples were examined by X-ray powder diffraction and then investigated using low-temperature calorimetry and IR spectroscopy. The low-temperature heat capacity data were used to obtain the vibrational entropies, and the line broadening of the IR spectra served as a tool to investigate the disordering enthalpy. These data were then used to calculate the configurational entropy as a function of temperature. The vibrational entropy does not change during the cation ordering phase transition from space group C2/c to P2/n at 865 °C but increases with a further temperature increase due to the reduction of short-range order. [ABSTRACT FROM AUTHOR]

Broadening coefficient of sulfur dioxide lines by carbon dioxide are calculated at room temperature for the ν1 + ν3 band with the rotational quantum numbers J and Ka varying in the ranges up to 100 and up to 20, respectively. Parameters of the semi-empirical method are determined from the analysis of experimental data. The broadening coefficients computed are in a good agreement with the literature data. [ABSTRACT FROM AUTHOR]

A great deal of attention is being paid by researchers to the multilevel modeling of complex gas-phase physicochemical processes occurring in the atmosphere, during combustion, and in plasma-chemical installations. One of the most important microscopic processes determining the transfer of radiation in these systems is the broadening of spectral lines in collisions of radiating atoms with atoms in the ground state. In this paper, we propose a formulation of the unified Franck-Condon theory of the broadening of spectral lines in gases in terms of the theory of slow atomic collisions and nonadiabatic transitions. This makes it possible to select the most efficient channels leading to the broadening of collisions based on the form of the adiabatic potential curves of the colliding atoms and, on this basis, apply fairly simple models developed in the theory of nonadiabatic transitions. As an example of using this approach, the center and wings of the of the spectral line contour of the Ar(3P1) → Ar(1S0) emission of excited argon atoms in their own gas are calculated. [ABSTRACT FROM AUTHOR]

The processes that control irradiation creep are dependent on the temperature and the rate of production of freely migrating point defects, affecting both the microstructure and the mechanisms of mass transport. Because of the experimental difficulties in studying irradiation creep, many different hypothetical models have been developed that either favour a dislocation slip or a mass transport mechanism. Irradiation creep mechanisms and models that are dependent on the microstructure, which are either fully or partially mechanistic in nature, are described and discussed in terms of their ability to account for the in-reactor creep behaviour of various nuclear reactor core materials. A rate theory model for creep of Zr-2.5Nb pressure tubing in CANDU reactors incorporating the as-fabricated microstructure has been developed that gives good agreement with measurements for tubes manufactured by different fabrication routes having very different microstructures. One can therefore conclude that for Zr-alloys at temperatures < 300 °C and stresses < 150 MPa, diffusional mass transport is the dominant creep mechanism. The most important microstructural parameter controlling irradiation creep for these conditions is the grain structure. Austenitic alloys follow similar microstructural dependencies as Zr-alloys, but up to higher temperature and stress ranges. The exception is that dislocation slip is dominant in austenitic alloys at temperatures < 100 °C because there are few barriers to dislocation slip at these low temperatures, which is linked to the enhanced recombination of irradiation-induced point defects. [ABSTRACT FROM AUTHOR]

We present Einstein coefficient spectra and a detailed-balance derivation of generalized Einstein relations between them that is based on the connection between spontaneous and stimulated emission. If two broadened levels or bands overlap in energy, transitions between them need not be purely absorptive or emissive. Consequently, spontaneous emission can occur in both transition directions, and four Einstein coefficient spectra replace the three Einstein coefficients for a line. At equilibrium, the four different spectra obey five pairwise relationships and one lineshape generates all four. These relationships are independent of molecular quantum statistics and predict the Stokes' shift between forward and reverse transitions required by equilibrium with blackbody radiation. For Boltzmann statistics, the relative strengths of forward and reverse transitions depend on the formal chemical potential difference between the initial and final bands, which becomes the standard chemical potential difference for ideal solutes. The formal chemical potential of a band replaces both the energy and degeneracy of a quantum level. Like the energies of quantum levels, the formal chemical potentials of bands obey the Rydberg-Ritz combination principle. Each stimulated Einstein coefficient spectrum gives a frequency-dependent transition cross-section. Transition cross-sections obey causality and a detailed-balance condition with spontaneous emission, but do not directly obey generalized Einstein relations. Even with an energetic width much less than the photon energy, a predominantly absorptive forward transition with an energetic width much greater than the thermal energy can have such an extreme Stokes' shift that its reverse transition cross-section becomes predominantly absorptive rather than emissive., Competing Interests: Competing interests statement:The authors declare no competing interest.

In‐cell NMR spectroscopy is a powerful tool to investigate protein behavior in physiologically relevant environments. Although proven valuable for disordered proteins, we show that in commonly used 1H‐15N HSQC spectra of globular proteins, interactions with cellular components often broaden resonances beyond detection. This contrasts 19F spectra in mammalian cells, in which signals are readily observed. Using several proteins, we demonstrate that surface charges and interaction with cellular binding partners modulate linewidths and resonance frequencies. Importantly, we establish that 19F paramagnetic relaxation enhancements using stable, rigid Ln(III) chelate pendants, attached via non‐reducible thioether bonds, provide an effective means to obtain accurate distances for assessing protein conformations in the cellular milieu. [ABSTRACT FROM AUTHOR]

As the development of current propulsion technology such as gas turbine and rocket chamber moving to higher working pressure, the radiative parameters of fuel, such as CH4 or CO, are required at elevated pressures, which in some cases are calculated without considering the pressure effect of line broadening. To investigate the pressure effect of line broadening on the radiative heat transfer, the radiative heat sources of a 1-D enclosure filled with CH4/CO and Planck mean absorption coefficients at elevated pressures were calculated using the statistical narrow band and line-by-line methods. The radiative parameters were conducted using high temperature molecular spectroscopic (HITEMP) 2019 (for CO) and HITEMP 2020 (for CH4) databases. The results showed that the pressure effect of line broadening on the calculations of radiative heat source of CH4 can be ignored when HITEMP 2020 database was used. For CO medium, the pressure effect of line broadening was over 40% at 30 atmosphere in all cases whichever methods and databases were used. The pressure broadening has a strong effect on the Planck mean absorption coefficient below 1000 K for CH4 and at the temperature of 500-900 K for CO at 30 atmosphere. The maximum pressure effects were 22% for CH4 and 18% for CO at 30 atmosphere, which illustrated the pressure effect of line broadening needed to be taken into account in the calculation of Planck mean absorption coefficient. [ABSTRACT FROM AUTHOR]

The method of medium frequencies has been applied to calculate the collisional half-widths of vibrational-rotational lines of a water molecule under helium pressure. The calculations have been performed for a wide range of rotational quantum numbers (J from 0 to 20: the calculations have been made by the method of medium frequencies, and J from 20 to 50: the interpolation of dependence on J has been performed). The spectral range has been from 500 to 10 000 cm–1. The H2O–He line broadening coefficients obtained by us have been compared with the literature data and a good agreement has been obtained. The coefficients of the temperature dependence of the lines half-widths have been calculated. [ABSTRACT FROM AUTHOR]

The stress state of a thin tungsten ribbon and magnetron-sputtered tungsten coatings on a ferrite steel substrate were investigated by X-ray tensometry (sin²ψ method). In-plane biaxial compressive stresses were revealed in the samples of the tungsten ribbon:  δy = −0.40 GPa and − 0.45 GPa in the rolling direction and δx = − 0.28 GPa and − 0.25 GPa in the direction perpendicular to the rolling direction from the front and back sides, respectively. The magnetron-sputtered tungsten coatings have in-plane equiaxial stresses, rotationally symmetric with respect to the surface normal ( δx = δy ). The stress magnitudes in the tungsten coatings are several times higher than those in the tungsten ribbon. The highest compressive stress (– 3.7 GPa) was found in a tungsten coating with a nominal thickness of 250 nm, in a coating with a thickness of 460 nm, the stress level was 1.5 times lower. The peculiarity of the analysis was that in the case of the tungsten ribbon, the line (310) was used, which certainly belongs to the precision region of the diffraction angles, while in the case of the tungsten coatings, due to the overlap of (310) α-W and (220) α-Fe lines, the lines (220) and (211) were used, which satisfy this condition to a lesser extent. The use of relatively soft Co-radiation (compared to Cu-radiation) somewhat mitigated this discrepancy. The stress-free lattice parameter (a0), corresponding to the undeformed cross section of the strain ellipsoid, was lower in the tungsten ribbon and higher in the coatings than the reference value for α -W; as the coating thickness increases, this difference increases. The reasons for these differences are discussed. Considering the broadening of the tungsten diffraction peaks, it was found that both the small size of the crystallites and the microstrain of the crystal lattice are the cause of this broadening in the samples of both groups, although the microstructure of the coatings is much more defective. [ABSTRACT FROM AUTHOR]

Correct pressure broadening is essential for modelling radiative transfer in atmospheres, however data are lacking for the many exotic molecules expected in exoplanetary atmospheres. Here we explore modern machine learning methods to mass produce pressure broadening parameters for a large number of molecules in the ExoMol data base. To this end, state-of-the-art machine learning models are used to fit to existing, empirical air-broadening data from the HITRAN database. A computationally cheap method for large-scale production of pressure broadening parameters is developed, which is shown to be reasonably (69%) accurate for unseen active molecules. This method has been used to augment the previously insufficient ExoMol line broadening diet, providing air-broadening data for all ExoMol molecules, so that the ExoMol database has a full and more accurate treatment of line broadening. Suggestions are made for improved air-broadening parameters for species present in atmospheric databases. [Display omitted] • A machine learning model is trained on the air-broadening data available in the HITRAN database. • A 69% reproduction of the HITRAN data within stated uncertainties is achieved. • Improvements in air broadening data are suggested for some species. • The algorithm is used to populate the ExoMol database. [ABSTRACT FROM AUTHOR]

In this paper, different aspects concerning anisotropy in Nuclear Magnetic Resonance (NMR) spectroscopy have been reviewed. In particular, the relevant theory has been presented, showing how anisotropy stems from the dependence of internal nuclear spin interactions on the molecular orientation with respect to the external magnetic field direction. The consequences of anisotropy in the use of NMR spectroscopy have been critically discussed: on one side, the availability of very detailed structural and dynamic information, and on the other side, the loss of spectral resolution. The experiments used to measure the anisotropic properties in solid and soft materials, where, in contrast to liquids, such properties are not averaged out by the molecular tumbling, have been described. Such experiments can be based either on static low-resolution techniques or on one- and two-dimensional pulse sequences exploiting Magic Angle Spinning (MAS). Examples of applications of NMR spectroscopy have been shown, which exploit anisotropy to obtain important physico-chemical information on several categories of systems, including pharmaceuticals, inorganic materials, polymers, liquid crystals, and self-assembling amphiphiles in water. Solid-state NMR spectroscopy can be considered, nowadays, one of the most powerful characterization techniques for all kinds of solid, either amorphous or crystalline, and semi-solid systems for the obtainment of both structural and dynamic properties on a molecular and supra-molecular scale. [ABSTRACT FROM AUTHOR]

The amount of water vapor in the terrestrial atmosphere is highly variable both spatially and temporally. In the tropics it sometimes constitutes 4–5% of the atmosphere. At the same time collisional broadening of spectral lines by water vapor is much larger than that by nitrogen and oxygen. Therefore, in order to accurately characterize and model spectra of the atmospheres with significant amounts of water vapor, the line‐shape parameters for spectral lines broadened by water vapor are required. In this work, the pressure‐broadening parameters (and their temperature‐dependent exponents) due to the pressure of water vapor for spectral lines of CO2, N2O, CO, CH4, O2, NH3, and H2S from both experimental and theoretical studies were collected and carefully reviewed. A set of semiempirical models based on these collected data was proposed and then used to estimate water broadening and its temperature dependence for all transitions of selected molecules in the HITRAN2016 database. Key Points: Water‐vapor broadening parameters for molecules in the HITRAN database are introduced for the first timeH2O‐broadening effects for spectral lines of different molecules are discussedProcedures describing how to work with new parameters using HITRANonline and HAPI are explained [ABSTRACT FROM AUTHOR]

Impurity‐induced structural distortion in SmB6 is suggested by Raman spectroscopy study on impurity‐controlled samples. Significant differences in the Raman spectra of single crystals SmB6(6N), synthesized with 99.9999%‐pure boron, and SmB6(3N), synthesized with 99.9%‐pure boron, are detected. While no noticeable differences are detected in the X‐ray diffraction of SmB6(3N) and SmB6(6N), all the Raman phonon modes of the T2g, Eg, and A1g of SmB6(3N) are clearly broader and shift to higher wavenumbers than those of SmB6(6N), and the T2g and Eg modes of SmB6(3N) show doublet features. Based on the high‐pressure Raman measurements and phonon calculation in uniaxial compression model, we argue that small amount of impurities in SmB6(3N) is enough to induce anisotropic distortion in the B6 octahedra, leading to peculiar behaviors in Raman spectrum of SmB6(3N). Our results may present a clue for understanding the current puzzles about SmB6 of various origins with different impurities. [ABSTRACT FROM AUTHOR]

Impurity‐induced structural distortion in SmB6 is suggested by Raman spectroscopy study on impurity‐controlled samples. Significant differences in the Raman spectra of single crystals SmB6(6N), synthesized with 99.9999%‐pure boron, and SmB6(3N), synthesized with 99.9%‐pure boron, are detected. While no noticeable differences are detected in the X‐ray diffraction of SmB6(3N) and SmB6(6N), all the Raman phonon modes of the T2g, Eg, and A1g of SmB6(3N) are clearly broader and shift to higher wavenumbers than those of SmB6(6N), and the T2g and Eg modes of SmB6(3N) show doublet features. Based on the high‐pressure Raman measurements and phonon calculation in uniaxial compression model, we argue that small amount of impurities in SmB6(3N) is enough to induce anisotropic distortion in the B6 octahedra, leading to peculiar behaviors in Raman spectrum of SmB6(3N). Our results may present a clue for understanding the current puzzles about SmB6 of various origins with different impurities. [ABSTRACT FROM AUTHOR]

The absorption line of the alkali metal is unstable in the atomic vapor cell, which is usually affected by the temperature and vapor pressure of the cell. However, the line shifting and broadening of the alkali metal in the atomic vapor cell could severely essential effect to the atomic sensors. This paper has systematically measured the broadening and shifting effect of Rubidium D 1 and D 2 line when the pressure of buffer gas N 2 is lower than 1 atm. The broadening coefficient of Rb D1 line on the N 2 pressure is 35.4MHz/torr, while the D2 line on the N 2 pressure is 21.2MHz/torr. When the N 2 pressure is near 1 atm, the shifting coefficients are 30.4MHz/K and -45.4MHz/K for D1 and D2 line through linear fit, respectively. The method in this paper, measuring the width shifting and broadening of the alkali metal absorb line, provides a way to verify the actual inner pressure of the vapor cell. [ABSTRACT FROM AUTHOR]