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Measuring the difference in nuclear charge radius of Xe isotopes by EUV spectroscopy of highly charged Na-like ions
摘要： The difference in the mean-square nuclear charge radius of xenon isotopes was measured utilizing a method based on extreme ultraviolet spectroscopy of highly charged Na-like ions. The isotope shift of the Na-like D1 (3s 2S1/2 ? 3p 2P 1/2) transition between the 124Xe and 136Xe isotopes was experimentally determined using the electron-beam ion-trap facility at the National Institute of Standards and Technology. The mass-shift and the ?eld-shift coef?cients were calculated with enhanced precision by the relativistic many-body perturbation theory and multicon?guration Dirac-Hartree-Fock method. The mean-square nuclear charge radius difference was found to be δ(cid:2)r 2(cid:3)136,124 = 0.269(42) fm2. Our result has smaller uncertainty than previous experimental results and agrees with the literature values.
关键词： Na-like ions,EUV spectroscopy,xenon isotopes,isotope shift,nuclear charge radius
更新于2025-09-23 15:21:01
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Calibration-free quantitative analysis of D/H isotopes with a fs-laser filament
摘要： The analytical characteristics of D/H isotopes with a fs-laser filament are investigated via analyzing a set of D-enriched water samples with D concentrations ranging from 0.5 to 20%. The filament emission spectra feature a narrow peak width and near-zero continuum spectral component. The characteristics of Balmer lines (a, b and g) are evaluated, and the Balmer-a line is selected for isotope analysis. Isotopic information is extracted from filament emission spectra through four different approaches: spectral deconvolution least squares algorithm (SDA), partial least squares regression-internal validation (PLSR-IV), partial least squares regression-cross validation (PLSR-CV) and partial least squares regression-calibration free (PLSR-CF). A multivariate spectral fitting procedure is established in the SDA. Fine structure components (FSCs) of Ha and Da were integrated in the SDA, and it shows improved analytical performance compared to the conventional SDA which is carried out by fitting the experimental spectra with two Lorentzian or Voigt functions. It is also found that the SDA with FSCs gives more accurate results than PLSR-IV and PLSR-CV. Furthermore, the analytical performance is significantly improved by the use of PLSR-CF, in which the PLSR calibration matrix is constructed with a synthetic spectra set. The improvement of accuracy for the given sample set further allows a calibration curve exhibiting an R2 exceeding 0.998 and a slop of 1.009. In addition, the calibration procedure with isotopically enriched standard samples is not necessary in PLSR-CF, demonstrating its flexibility over classical chemometric approaches.
关键词： fs-laser filament,PLSR,spectral deconvolution,calibration-free analysis,Balmer lines,D/H isotopes
更新于2025-09-23 15:21:01
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Perdeuterated conjugated polymers for ultralowa??frequency magnetic resonance of OLEDs
摘要： Formation of excitons in OLEDs is spin dependent and can be controlled by electron-paramagnetic resonance, affecting device resistance and electroluminescence yield. We explore electrically detected magnetic resonance in the regime of very low magnetic fields (<1mT). A pronounced feature emerges at zero field in addition to the conventional spin-? Zeeman resonance for which the Larmor frequency matches that of the incident radiation. By comparing a conventional π-conjugated polymer as the active material to a perdeuterated analogue, we demonstrate the interplay between zero-field feature and local hyperfine fields. The zero-field peak results from a quasistatic magnetic-field effect of the RF radiation for periods comparable to the carrier-pair lifetime. Zeeman resonances are resolved down to 3.2MHz, approximately twice the Larmor frequency of an electron in Earth’s field. However, since reducing hyperfine fields sharpens the Zeeman peak at the cost of an increased zero-field peak, we suggest that this result constitutes a fundamental low-field limit of magnetic resonance in carrier-pair-based systems. OLEDs offer an alternative solid-state platform to investigate the radical-pair mechanism of magnetic-field effects in photochemical reactions, allowing models of biological magnetoreception to be explored by measuring spin decoherence directly in the time domain.
关键词： Deuteration,Magnetic resonance,Isotopes,Conjugated Polymers,Organic light-emitting diodes
更新于2025-09-23 15:19:57
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Fast offline data reduction of laser ablation MC-ICP-MS Sr isotope measurements via the interactive Excel-based spreadsheet a??SrDRa??
摘要： Strontium isotopes are applied to a wide range of scientific fields and to different types of sample materials, providing valuable information foremost about provenance and age, but also on diagenetic processes and mixing relationships between different Sr reservoirs. The development of in-situ analytical techniques, such as laser ablation ICP-MS, has improved our understanding of Sr isotope variability in several field of application, because of the possibility to discriminate small-scale changes and their spatial distribution. However, large outputs of Sr isotope data are produced by laser ablation MC-ICP-MS systems, which necessitate of multiple offline steps to correct and assess the data. This requires the availability of simple and user-friendly tools, easily manageable also by non-specialists. With this in mind, we developed SrDR, an Excel-based interactive data reduction spreadsheet (‘SrDR’, Sr-Data-Reduction) for the processing of Sr isotopes measured by LA-MC-ICP-MS. The SrDR spreadsheet is easily customizable (a) to meet user-specific analytical protocols, (b) for different instruments (i.e. Nu Plasma vs. Neptune), and (c) for diverse target materials (e.g. Rare Earth Elements enriched or depleted samples). We include also several examples relevant to low and high temperature geochemistry fields - a fossil tooth, a modern seashell, a speleothem sample and plagioclase crystals - to show how different sample materials are corrected for different interfering masses.
关键词： Strontium isotopes,SrDR,Excel spreadsheet,data reduction,LA-MC-ICP-MS
更新于2025-09-23 15:19:57
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Accumulation of 13C-labelled phenanthrene in phytoplankton and transfer to corals resolved using cavity ring-down spectroscopy
摘要： Polycyclic aromatic hydrocarbons (PAHs) are widespread pollutants in marine ecosystems including threatened and potentially sensitive coral reefs. Lower organisms such as phytoplankton, known to bioconcentrate PAHs, could serve as potential entry points for these chemicals into higher trophic levels. Here, we present a novel method using a 13C-labelled PAH and cavity ring-down spectroscopy (CRDS) to investigate accumulation, uptake rates and trophic transfer of PAHs in corals, which are key organisms to sustain biodiversity in tropical seas. We quantified the accumulation of 13C-phenanthrene in the marine microalga Dunaliella salina, and in the coral Acropora millepora after diffusive uptake from seawater or dietary uptake via labelled D. salina. Additionally, we monitored the photophysiological health of D. salina and A. millepora during phenanthrene exposure by pulse-amplitude modulation (PAM) fluorometry. Dose-dependent accumulation of 13C-phenanthrene in the microalga showed a mean bioconcentration factor (BCF) of 2590 ± 787 L kg?1 dry weight. Corals accumulated phenanthrene from both exposure routes. While uptake of 13C-phenanthrene in corals was faster through aqueous exposure than dietary exposure, passive diffusion showed larger variability between individuals and both routes resulted in accumulation of similar concentrations of phenanthrene. The 13C-PAH labelling and analysis by CRDS proved to be a highly sensitive method. The use of stable isotopic label eliminated additional toxicity and risks by radioactive isotopic-labelling, and CRDS reduced the analytical complexity of PAH (less biomass, no extraction, fast analysis). The simultaneous, precise quantification of both carbon content and 13C/12C ratio (δ13C) enabled accurate determination of 13C-phenanthrene accumulation and uptake rate. This is the first study to provide empirical evidence for accumulation of phenanthrene in a phytoplankton-coral food chain.
关键词： Phenanthrene,Bioaccumulation,PAHs,Phytoplankton,Stable isotopes,Corals
更新于2025-09-23 15:19:57
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Perdeuterated conjugated polymers for ultralowa??frequency magnetic resonance of OLEDs
摘要： The formation of excitons in OLEDs is spin dependent and can be controlled by electron-paramagnetic resonance, affecting device resistance and electroluminescence yield. We explore electrically detected magnetic resonance in the regime of very low magnetic fields (< 1 mT). A pronounced feature emerges at zero field in addition to the conventional spin-1=2 Zeeman resonance for which the Larmor frequency matches that of the incident radiation. By comparing a conventional p-conjugated polymer as the active material to a perdeuterated analogue, we demonstrate the interplay between the zero-field feature and local hyperfine fields. The zero-field peak results from a quasistatic magnetic-field effect of the RF radiation for periods comparable to the carrier-pair lifetime. Zeeman resonances are resolved down to 3.2 MHz, approximately twice the Larmor frequency of an electron in Earth(cid:3)s field. However, since reducing hyperfine fields sharpens the Zeeman peak at the cost of an increased zero-field peak, we suggest that this result may constitute a fundamental low-field limit of magnetic resonance in carrier-pair-based systems. OLEDs offer an alternative solid-state platform to investigate the radical-pair mechanism of magnetic-field effects in photochemical reactions, allowing models of biological magnetoreception to be tested by measuring spin decoherence directly in the time domain by pulsed experiments.
关键词： conjugated polymers,deuteration,magnetic resonance,isotopes,organic light-emitting diodes
更新于2025-09-23 15:19:57
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Radiology, Lasers, Nanoparticles and Prosthetics || 2. Nuclei and isotopes
摘要： In Chapters 5 to 12 nuclear methods in medicine are discussed either for imaging (scintigraphy, SPECT, PET) or for radiation treatment of cancerous tissues (proton and neutron irradiation, brachytherapy). It is therefore appropriate to first introduce some basic properties of nuclides and isotopes, and in particular of radioactive isotopes which are used in nuclear medicine. This chapter is not intended to replace a textbook on nuclear physics. But it provides sufficient background information for better understanding the subsequent chapters. Handling of radiation in general and application of radioactive isotopes also requires a detailed knowledge of radiation dose and radiation safety, which are topics of Chapter 4.
关键词： scintigraphy,medicine,SPECT,neutron irradiation,PET,brachytherapy,radiation safety,proton irradiation,nuclides,cancerous tissues,isotopes,radioactive isotopes,radiation dose,imaging,nuclear medicine,nuclear methods,radiation treatment
更新于2025-09-19 17:13:59
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Multi-Resonance Induced Thermally Activated Delayed Fluorophores for Narrowband Green OLEDs
摘要： Biogeochemical silicon (Si) cycling in coastal systems is highly influenced by anthropogenic perturbations in recent decades. Here, we present a systematic study on the distribution of stable Si isotopes of dissolved silicate (δ30SiDSi) in a highly eutrophic coastal system, the Baltic Sea. Besides the well-known processes, diatom production and dissolution regulating δ30SiDSi values in the water column, we combined field data with a box model to examine the role of human disturbances on Si cycling in the Baltic Sea. Results reveal that (1) damming led to increased δ30SiDSi values in water but had little impacts on their vertical distribution; (2) decrease in saltwater inflow due to enhanced thermal stratification had negligible impacts on the δ30SiDSi distribution. An atypical vertical distribution of δ30SiDSi with higher values in deep water (1.57–1.95‰) relative to those in surface water (1.24–1.68‰) was observed in the central basin. Model results suggest the role of enhanced biogenic silica (BSi) deposition and subsequently regenerated dissolved silicate (DSi) flux from sediments. Specifically, eutrophication enhances diatom production, resulting in elevated exports of highly fractionated BSi to deep water and sediments. In situ sedimentary geochemical processes, such as authigenic clay formation, further fractionate Si isotopes and increase pore-water δ30SiDSi values, which then leads to pore-water DSi flux carrying higher δ30SiDSi compositions into deep water. Our findings provide new quantitative information on how the isotope-based Si cycle responds to human perturbations in coastal seas and shed lights on shifts of Si export to open ocean.
关键词： human disturbance,Baltic Sea,silicon isotopes,coastal sea,biogeochemical silicon cycle
更新于2025-09-19 17:13:59
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Experimental investigation on nuclear reactions using a laser-accelerated proton and deuteron beam
摘要： We report an experimental investigation on nuclear reactions using an intense, ultra-short laser-accelerated proton and deuteron beam generated by the interaction of 25 fs, 150 TW Ti: sapphire laser pulse with normal thin foils and foils containing deuterium atoms. The production of a positron-emitting short-lived 11C radio-isotope from the interaction of protons and deuterium ions with a solid boron palette by means of 11B (p, n)11C and 10B (d, n)11C nuclear reactions was studied. The maximum radioactivity in the optimized laser irradiation condition was found to be 5.2 kBq per laser shot, which corresponds to ～9 × 106 atoms of 11C isotopes using the 11B (p, n)11C reaction. The relative ef?ciency of 11C production using a proton and deuteron beam was also explored experimentally. About 30 % enhancement in 11C activity was observed with CD2 coated targets. It was also found that because of the relatively low deuteron energy threshold of the reaction 10B (d, n)11C, even the low energy part of the accelerated deuterons in the spectrum can be used for ef?cient 11C production. In the same setup, the proton-induced fusion reaction in the boron target (p + 5B11 ? 3α + 8.7 MeV) was also studied. The resultant fusion yield and alpha particle energy spectrum was measured.
关键词： p?11B fusion,laser particle acceleration,positron emission tomography (PET) isotopes,laser driven ion acceleration,laser plasma interaction,laser induced nuclear reactions,high intensity lasers
更新于2025-09-19 17:13:59
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Multivariate determination of 10B isotopic ratio by laser-induced breakdown spectroscopy using multiple BO molecular emissions
摘要： Measurements of boron isotopic ratios have been investigated using LIBS, and combined LIBS and Molecular laser-induced fluorescence (MLIF). Mixtures of various ratios of research grade H3 11BO3 and H3 10BO3 in pellet form were interrogated with a Q-switched Nd:YAG laser operating at 532 nm. The resulting plasma was examined for their BO molecular bands in the 254–262 nm and 266–276 nm wavelength ranges. A minimum of three band heads of the β system B2Σ → X2Σ transitions were identified. The rovibronic isotopic shifts of the corresponding bands were measured and were conclusively compared to the literature. MLIF was applied to LIBS emission lines covering 253–271 nm to enhance some band heads, selectively. Both LIBS and LIBS-MLIF emissions were subject to multivariate statistical analysis to predict 10B isotopic ratios. Two PLS regression calibration models were examined to better examine the effects, sensitivity, accuracy of the laser-produced plasma excitation modalities based models through the figure of merit. For the full calibration set (21 samples), the root mean square error of cross-validation (RMSECV), the pseudo univariate LOD (LODpu) and the LOD interval ([LODmin, LODmax]) for 10B isotopes were improved from 1.61%, 4.81%, [2.64%, 3.49%] 10B isotopic ratio, respectively for LIBS to 0.98%, 2.40%, [2.19%, 2.81%] 10B isotopic ratio, respectively for LIBS-MLIF. However, using a random subset of the samples (14) as a calibration set and the rest as a test set, the root mean square error of prediction of 10B isotopic ratio in the test set improved from 2.95% to 1.16% 10B isotopic ratio, respectively for LIBS and LIBS-MLIF; and the LOD interval improved from [2.45%, 2.69%] to [1.88%, 2.12%] 10B isotopic ratio when calculated with cross-validated residual variance. Moreover, the prediction error of a test set improved from 2.95% for LIBS to 1.16% for LIBS-MLIF.
关键词： Molecular laser-induced fluorescence,LIBS-MLIF,Limit of detection interval,Laser-induced breakdown spectroscopy,Boron isotopes,Molecular band
更新于2025-09-16 10:30:52