Atomic Source Research Articles

Backscattering of Ions Impacting Ganymede’s Surface as a Source for Energetic Neutral Atoms

Jupiter’s largest moon Ganymede has its own intrinsic magnetic field, which forms a magnetosphere that is embedded within Jupiter’s corotating magnetospheric plasma. This scenario has been shown to lead to complex ion precipitation patterns that have been connected to heterogeneous space weathering across Ganymede’s surface. We present the first simulations of energetic neutral atoms (ENAs) from backscattered H, O, and S ions, accounting for magnetospheric plasma precipitation and Ganymede’s heterogeneous surface composition. Our model shows that backscattering introduces significant atomic H and O populations to Ganymede’s ENA environment, which will allow remote observation of ion–surface interactions at Ganymede. There are distinct differences between H ENA emissions at Ganymede and the Moon, with orders of magnitude lower fluxes below 1 keV but a significant tail above 1 keV. Backscattered H ENAs will also dominate over sputtered H contributions above energies of around 1 keV, while O ENAs are less likely to be distinguished from sputtered ENAs. The backscattered H ENAs thus represent a promising candidate for studying the plasma–surface interaction on Ganymede with future observations of ESA’s JUICE mission.

Continuous cold rubidium atomic beam with enhanced flux and tunable velocity.

We present a cold atomic beam source based on a two-dimensional (2D)+ magneto-optical trap (MOT), capable of generating a continuous cold beam of 87Rb atoms with a flux up to 4.3 × 109 s-1, a mean velocity of 10.96(2.20) m/s, and a transverse temperature of 16.90(1.56) µK. Investigating the influence of high cooling laser intensity, we observe a significant population loss of atoms to hyperfine-level dark states. To account for this, we employ a multiple hyperfine level model to calculate the cooling efficiency associated with the population in dark states, subsequently modifying the scattering force. Simulations of beam flux at different cooling and repumping laser intensities using the modified scattering force are in agreement with experimental results. Optimizing repumping and cooling intensities enhances the flux by 50%. The influence of phase modulation on both the pushing and cooling lasers is experimentally studied, revealing that the mean velocity of cold atoms can be tuned from 9.5 m/s to 14.6 m/s with a phase-modulated pushing laser. The versatility of this continuous beam source, featuring high flux, controlled velocity, and narrow transverse temperature, renders it valuable for applications in atom interferometers and clocks, ultimately enhancing bandwidth, sensitivity, and signal contrast in these devices.

Photodissociation of the CH2Br radical: A theoretical study.

Bromine atom (Br) reactions lead to ozone depletion in the troposphere and stratosphere. Photodegradation of bromocarbons is one of the main sources of bromine atoms in the atmosphere. Here, we use high-level abinitio methods, including spin-orbit effects, to study the photodissociation of the CH2Br radical. All possible fragmentation pathways, namely CH2Br + hν → CH2 + Br, HCBr + H, and CBr + H2, have been analyzed. Potential-energy curves of the ground and several excited electronic states along the corresponding dissociating bond distance of each pathway have been calculated. Considering the actinic fluxes of solar irradiation in the troposphere and in the stratosphere in the relevant range of frequencies, it is found that the first five excited states of CH2Br can be accessed from the ground state. Analysis of the potential curves shows that the pathways producing CH2 + Br and HCBr + H can proceed through a fast direct dissociation mechanism, while the pathway leading to CBr + H2 involves much slower dissociation mechanisms like internal conversion between electronic states, predissociation, or tunneling through exit barriers. The main implications are that the two faster channels are predicted to be dominant, and the slower pathway is expected to be less relevant. The tropospheric and stratospheric solar actinic fluxes also allow for further dissociation of the HCBr and CBr fragments, generating additional Br atoms, provided that they survive possible collisions with other atmospheric reagents. Finally, we discuss the possible effect of each of the three CH2Br dissociation pathways on the depletion of atmospheric ozone.

Electrocatalytic Epoxidation of Cyclooctene on Surface Modified Ni Foam Using Water as Oxygen Source.

Electrochemical epoxidation of olefins using water as an oxygen atom source is emerging as an alternative approach for an atom economic and sustainable method towards a highly selective synthesis of epoxides. We report an electrochemical procedure for epoxidation of cyclooctene using water as the sole oxygen atom source over a sodium dodecyl sulfonate (SDS) modified nickel hydroxide Ni(OH)2 catalyst directly grown on Ni foam. The SDS modification facilitates the mass transfer of cyclooctene towards the anode, thus achieving a 2.5-fold higher conversion with more than 90 % selectivity towards the corresponding epoxide compared with pure Ni(OH)2 catalyst.

Ti(III)-Catalyzed Anti-Markovnikov Reduction of Epoxides with Borohydride.

We have developed a Ti catalyst that carries out the anti-Markovnikov reduction of a wide range of epoxides; [BH4]- is used as both the electron and the hydrogen atom source. It requires only mild conditions and accommodates a broad range of epoxide substrates. The Ti catalyst is readily available and is environmentally friendly.

Reduction of Irreversible Capacity in Lithium-ion Batteries

This article is focused on a research of negative materials for Lithium-ion batteries. In the research are considered methods, which can lead to enhance capacity of Lithium-ion batteries. The increase of the battery capacity is based on reduction of irreversible capacity. The majority of Li-ion batteries which are used in this time has negative electrode make from graphite. On interface between electrolyte and graphite electrode originates the SEI layer (Solid-Electrolyte Interphase), this layer is the cause of irreversible capacity of graphite. This layer is indispensable for appropriate battery function but for creating this layer is consumed almost one-third potential capacity of Li-ion cell. In our research we attempted to prepare the material which would reduce these capacity losses. Was designed a concept where n-butyllithium (C4H9Li) reagent behaves as the source of lithium atoms and graphite acts like acceptor of lithium atoms. This process is called „lithiation“, our conception presents n-butyllithium like oxidative reagent which is able to reduce graphite material by Li atoms. Lithium atoms are intercalated between graphite sheets (as at charging process), resulting of this process is new lithiated electrode material which can be used for prepare of negative electrode for Li-ion cells.

Lewis Base‐Boryl Radicals Promoted Selective Mono‐ and Di‐ Hydrodechlorination of Trichloroacetamides and Acetates

AbstractMono and dichloro‐substituted organic molecules are shown to possess significant roles in various fields, especially in medicinal chemistry. One approach to synthesizing these compounds involves the selective dechlorination of easily prepared trichloromethyl compounds. Nevertheless, developing a practical approach that allows selective mono‐ and dihydrodechlorination is a challenging task. Herein, we introduced a method for selective mono‐ and dihydrodechlorination of trichloroacetamides and acetates which was promoted by two different Lewis base‐boryl radicals. Accordingly, 4‐dimethylaminopyridine (DMAP)‐borane enabled mono‐substitution of chlorine atom by hydrogen while dihydro‐substitution of chlorine atoms was promoted by N‐heterocyclic carbene (NHC)‐boryl radical. Using deuterated Lewis base‐borane as deuterium atom source, mono‐ and dideuterodechlorination were also successfully took place. This protocol features broad substrate scope and operates under mild reaction conditions.

Unprecedented sulfenic acid-dependent hydroxyl radical production and DNA damage by N-heterocyclic thiols and H2O2

The decomposition of H2O2 to produce the highly-reactive hydroxyl radical (•OH) is one of most well-known pathways to generate •OH, which can be readily activated by transition metal ions and haloquinones, but rarely by N-heterocyclic thiol compounds. Here we found, unexpectedly, that DNA oxidative damage can be induced by H2O2 together with 2-mercaptopyridine (PySH), a typical N-heterocyclic thiol compound widely-used in industry, agriculture, medicine and organic synthesis, which was found to be mainly due to production of •OH independent of transition metal ions. 2,2′-Dithiodipyridine, pyridine-2-sulfenic acid (PySOH), pyridine-2-sulfinic acid and pyridine-2-sulfonic acid were step-wisely produced during the reaction of PySH/H2O2, and the source and origin of the oxygen atoms inserted into these intermediates and products were found to be from H2O2 by oxygen-18 isotope labeling technique coupled with ESI-Q-TOF-MS analysis. More importantly, among all the transient intermediates, PySOH was found to be the key one directly responsible for •OH production from PySH/H2O2. Analogous results were observed with several PySH derivatives. This is the first report on an unprecedented sulfenic acid-dependent •OH production from the activation of H2O2 by N-heterocyclic thiol compounds, which may have important chemical, biological and biomedical implications for future study of these widely-used compounds.

Utilization of Magonia pubescens extracts in the synthesis of rhodium NPs on Fe3O4@MgO support: A novel catalyst for 4-nitrophenol hydrogenation

This study reports the development of three distinct nanoparticulate catalysts, each comprising a biosynthesized Fe3O4 nanoparticle magnetic core with an average diameter of 17 nm, showcasing superparamagnetic behavior. This magnetic core was further encased in a spherical magnesium oxide (MgO) layer through a bio-inspired strategy, leading to the Fe3O4@MgO support structure. Rhodium (Rh) nanoparticles, with diameters between 1.0 and 1.5 nm, were then fabricated to act as the main catalytic entities. These were subsequently affixed to the Fe3O4@MgO support, yielding Fe3O4@MgO-Rh, using three distinct methodologies. Remarkably, the bio-inspired processes employed for the creation of Fe3O4@MgO-Rh harnessed the infusion and extract from Magonia pubescens A St. Hil leaves, colloquially termed “Timbó”. These natural extracts played dual roles as reducing and stabilizing agents during the catalyst generation, leading to three variants: CI, CW, and CS. Comprehensive characterization of these catalysts was achieved using XPS, TEM, EDS, and VSM techniques. The ensuing evaluation involved the hydrogenation of 4-nitrophenol, which served to assess the efficiency and resilience of the bio-inspired catalysts vis-à-vis conventionally-produced counterparts. Notably, under benign conditions of a molecular H2 atmosphere (an ecologically sound hydrogen atom source) and moderate temperatures (60 °C), conversion rates exceeding 97 % were consistently observed for the substrate within a time frame of 0 to 15 min. For a more granular comparison of efficiency among the rhodium-centric catalysts, Turnover Frequency (TOF) and Total Turnover Number (TTON) computations were undertaken. Herein, the CI catalyst, originating from infusion, displayed a TTON value of 1263.24, underscoring its preeminence in 4-NF hydrogenation reactions. This was closely trailed by the CS catalyst, which boasted a TTON of 873.63, synthesized with a commercial surfactant.

Laser optogalvanic spectroscopy of lead lines — Isotope shifts and hyperfine structure studies

Six atomic lines of Pb I in the 569–612 nm wavelength range and two lines of Pb II in the wavelength range of 560-608 nm were examined using optogalvanic spectroscopy. A hollow cathode discharge lamp was the source of Pb atoms and ions. Hyperfine structure constants were measured for levels associated with the observed transitions. The result of the research was also the determination of isotope shifts in the studied lines. The experimental data we have obtained complement or correct the existing database. We determined six values of the A constants of the hyperfine structure of Pb I, including one value determined for the first time and clarified one value of the A constant for Pb II. We determined seven new values of isotopic shifts between individual isotopes for two Pb I lines and one Pb II line. Furthermore, ab-initio MCDHF calculations of the observed isotope shifts and hyperfine structure constants were performed. Theoretical results are in good agreement with experimental data.

Improving the Quality of Ceramic Products by Removing the Defective Surface Layer

The surface of ceramic products manufactured using diamond grinding is replete with shallow scratches, deep grooves and other defects. The thickness of the defective layer amounts to 3–4 µm and it must be removed to increase wear resistance of the products when exposed to intense thermomechanical loads. In this study, removal of the defective layers from samples made of ZrO2, Al2O3 and Si3N4 with a beam of fast argon atoms was carried out with a stripping rate of up to 5 µm/h. To prevent contamination of the source of fast argon atoms by the sputtered dielectric material, the beam was compressed and passed to the sample through a small hole in a wide screen. Due to the removal of the defective layer, abrasive wear decreased by an order of magnitude and the adhesion of coatings deposited on the cleaned ceramic surfaces improved significantly.

Preparation and measurement of a sandwiched Sn atomic beam source for laser resonance ionization mass spectrometry.

Isotope analysis of Sn plays a crucial role in geochemical studies and in monitoring nuclear contamination. Nevertheless, prevalent analytical techniques for examining Sn isotopes encounter the issue of isobaric interference, markedly impacting the accuracy of the test results. Laser resonance ionization mass spectrometry (LRIMS) can effectively overcome the difficulties associated with the isobaric interference inherent in commercial mass spectrometry. In this paper, different amounts of Sn were prepared on Re filaments by electrodeposition and tested via LRIMS. The results showed that the average detection efficiency of LRIMS decreased with increasing total Sn content from 1 μg to 4 μg, and the fluctuations in the test results among the samples increased significantly. Therefore, the electrodeposition process, as well as the composition and morphology of the deposits were characterized by SEM, EDS and XPS; results showed that the degradation of the samples with increasing Sn content was attributed to the complexity of the composition, micro-structure, valence of the deposits, and the interference of various elements. To cope with the anomalies encountered above, the deposits were heat-treated at 600 °C in a hydrogen atmosphere to eliminate detrimental impurities, like Cl, and Sn was effectively reduced to an almost singular atomic state. Furthermore, a titanium layer was covered on the surface of the heat-treated deposit by magnetron sputtering. Ultimately, a highly efficient and stable Sn atomic beam source with a sandwiched structure has been successfully developed and exhibits broad application prospect.

Research progress of ultracold ion source

<sec>Nanobeam is an advanced technology for preparing charged ion beams with spot diameters on a nanometer scale, and mainly used for high-resolution and high-precision ion beam analysis, ion beam fabrication and ion beam material modification research. The nanobeam devices play an important role in realizing material analysis, micro/nano fabrication, microelectronic device manufacturing and quantum computing. The high-quality ion source is one of the key components of nanobeam device, the performance of which directly affects the resolution and precision of the nanobeam system. However, the traditional ion source used in this system is limited to available ionic species, large energy spread and complex structure. These issues hinder their ability to meet emerging application scenarios that require multi-ion types and high resolution. This emphasizes the importance of creating newion sources as soon as possible.</sec><sec>With the development of laser cooling technology, ultracold ions with temperatures in the range of mK or even μK can be obtained based on photoionization of cold atoms and laser cooling of ions. The typical characteristics of low temperature and easy operation greatly promote the emergence of ultracold ion sources. The ultracold ions exhibit extremely small transverse velocity divergence, which can significantly enhance the brightness and emittance quality parameters of the ion source, bringing great opportunities for innovating nano-ion beam technology. Therefore, the research on ultracold ion sources is of great significance for achieving high-quality ion sources with higher brightness, smaller size, lower energy dispersion, more diverse ion species, and simplified structure. Here, we introduce the important achievements in basic research and application technology development of magneto-optical trap ion sources, cold atomic beam ion sources, and ultracold single ion sources from the aspects of preparation principles, generation methods, and typical applications, and review the recent research progress of ultracold ion sources. Finally, we provide an outlook on the future development and application prospects of ultracold ion sources.</sec>

Ion-collection characteristics of photoplasma for atomic vapor laser isotope separator module in electrostatic fields

The laser-based isotope separation process is currently pursued to enrich precursor medical isotopes like lutetium-176 and ytterbium-176. India has successfully produced radionuclide lutetium-177 for clinical use by neutron activation. Atomic vapor laser isotope separation (AVLIS) is used as the enrichment technology. Understanding the physics and technology of processes, like atomic-beam generation, photoplasma production, and ion collection, is essential to designing any AVLIS module. So, a stand-alone research facility was developed before the production plant. This article describes the facility and the experimental and theoretical studies of ion collection in electrostatic fields using barium as the working element. Two types of ion extractors, plate–photoplasma–plate and plate–photoplasma–grid–plate, were designed and fabricated. A model of photo-ion collection in these electrostatic ion extractors was arrived at. Scaling of the initial photo-ion densities and the electric fields is crucial to photoplasma evolution spanning single-particle to collective regimes. Estimates of ion-collection rates of the Indian AVLIS modules for lutetium-176 and ytterbium-176 were carried out. By invoking plasma physics, the technological aspect of producing enriched isotopes was solved by judiciously integrating the atom source, laser system, photoplasma, and ion-extractor geometries. Limitations of the electrostatic ion extractors were also flagged.

Efficient cold atom source from a single-layer atom chip

Efficient cold atom source from a single-layer atom chip

Dispersion-induced cooperative hydrogen atom transfer for radical iodoalkylation.

Described herein is a novel visible-light-promoted three-component radical iodo-alkylative cyclization of alkynes using iodoform as a bifunctional iodine atom source. Visible-light irradiation of a polar-polar interaction complex of iodoform with malonate enables the cooperative hydrogen atom transfer process to generate alkyl radical and trigger a cascade reaction sequence.

Effect of atom diffusion on the efficiency of Bragg diffraction in atom interferometers.

The transition efficiency of atomic Bragg diffraction as mirrors and beam splitters in Bragg atom interferometers plays an essential role in impacting the fringe contrast and measurement sensitivity. This can be attributed to the properties of atomic sources, Bragg pulse shapes, the pulse duration, and the relative position deviation of the atoms and Bragg pulses. Here, we investigate the effect of the atomic source's diffusion and velocity width on the efficiency of Bragg diffraction of the moving cold atomic cloud. The transfer efficiency of Bragg mirrors and beam splitters are numerically simulated and experimentally measured, which are well consistent in comparison. We quantify these effects of atomic diffusion and velocity width and precisely compute how Bragg pulses' efficiencies vary as functions of these parameters. Our results and methodology allow us to optimize the Bragg pulses at different atomic sources and will help in the design of large momentum transfer mirrors and beam splitters in atom interferometry experiments.

Synthesis of N-Doped Graphene Photo-Catalyst for Photo-Assisted Charging of Li-Ion Oxygen Battery.

In this work, nitrogen (N)-doped graphene film is synthesized, as a photo-catalyst, on one side of the copper foam by chemical vapor deposition and the copper foam is directly used as an electrode after porous Pd@rGO cathode loading to the other side of the foam for the photo-assisted charging of the Li-ion oxygen battery. The amount of urea (CO(NH2)2), which is used as N atom source, is optimized to get maximum photo-anodic currents from the n-type graphene films. The optical band gap and the valance band edge potential of the optimized N-doped graphene film are determined as 2.00eV and 3.71VLi+/Li, respectively. X-ray photoelectron spectra provided that the atomic percent of N atoms in the graphene film is 1.34% and the graphitic, pyrrolic and pyridinic N atom percentages are 54.01%, 42.20% and 3.79%, respectively. The photo-assisted charging tests indicated that the N-doped graphene film photo-catalyst reduced the charging potential significantly even at 1000mAg-1 (0.1mAcm-2) current density and improved the cyclic discharge-charge performance of the Li-ion oxygen battery considerably.

The PEPSI Exoplanet Transit Survey (PETS) – IV. Assessing the atmospheric chemistry of KELT-20b

ABSTRACT Most ultra-hot Jupiters (UHJs) show evidence of temperature inversions, in which temperature increases with altitude over a range of pressures. Temperature inversions can occur when there is a species that absorbs the stellar irradiation at a relatively high level of the atmospheres. However, the species responsible for this absorption remains unidentified. In particular, the UHJ KELT-20b is known to have a temperature inversion. Using high resolution emission spectroscopy from LBT/PEPSI we investigate the atomic and molecular opacity sources that may cause the inversion in KELT-20b, as well as explore its atmospheric chemistry. We confirm the presence of Fe i with a significance of 17σ. We also report a tentative 4.3σ detection of Ni i. A nominally 4.5σ detection of Mg i emission in the PEPSI blue arm is likely in fact due to aliasing between the Mg i cross-correlation template and the Fe i lines present in the spectrum. We cannot reproduce a recent detection of Cr i, while we do not have the wavelength coverage to robustly test past detections of Fe ii and Si i. Together with non-detections of molecular species like TiO, this suggests that Fe i is likely to be the dominant optical opacity source in the dayside atmosphere of KELT-20b and may be responsible for the temperature inversion. We explore ways to reconcile the differences between our results and those in literature and point to future paths to understand atmospheric variability.

Direct Access to Quinazolines and Pyrimidines from Unprotected Indoles and Pyrroles through Nitrogen Atom Insertion.

Recent advances in single-atom insertion reactions have opened up new synthetic approaches for molecular diversification. Developing innovative strategies to directly transform biologically relevant molecules, without any prefunctionalization, is key to further expanding the scope and utility of such transformations. Herein, the direct access to quinazolines and pyrimidines from the corresponding unprotected 1H-indoles and 1H-pyrroles is reported, relying on the implementation of lithium bis(trimethylsilyl)amide (LiHMDS) as a novel nitrogen atom source in combination with commercially available hypervalent iodine reagents. Further application of this strategy in late-stage settings demonstrates its potential in lead structure diversification campaigns.