Samarium Atoms Research Articles

The SPES Laser Ion Source: Time Structure and Laser Enhancement Measurements with Sm+ beam

A two-step resonance photo-ionization scheme has been used to ionize samarium atoms in the SPES tantalum hot-cavity ion source. The effect of the ion load on the ion beam time structure and the laser enhancement of the ion yield has been studied at different ion source temperatures. Generally, the introduction of more positive ions (ion load) affects negatively the overall confinement of the laser ions inside the volume of the ion source. Possible enhancement of the laser ion confinement through the introduction of neutrals is observed as well. The ion load is also observed to affect the confinement in the transfer line much more than in the hot cavity. Measurement of the time structure with inverted polarity of the cavity DC heating supply confirmed the significance of the longitudinal potential for ion extraction. The laser enhancements of the ion yield are found to be sensitive to the ion load at low operating temperature of the ion source i.e. 1800°C, whereas at 2050°C and 2200°C, they are relatively stable till an ion load value of 1.2 µA.

Real Structure, Magnetism and Chemical Bonding of SmSi3‐x

New metastable SmSi3‐x (x = 0‐0.05) is obtained by high‐pressure high‐temperature synthesis (9.5 GPa, 870‐1270 K). Powder diffraction data refinements reveal that the crystal structure of SmSi3 is isotypic to that of YbSi3 (space group I4/mmm, a = 7.23634(5) Å, c = 11.0854(1) Å). In the crystal structure, two types of Si2 dumbbells agglomerate into layers, which embed the samarium atoms. At ambient pressure, SmSi3 decomposes exothermally upon heating into Si and SmSi2‐x. Single‐crystal structure refinements of a specimen SmSi3‐x (x=0.05) reveal considerable electron density, which is not accounted for by the YbSi3 model. The additional maxima can be assigned to disorder which affects the samarium positions and induces silicon vacancies. Scanning transmission electron microscopy experiments evidence that the disorder can be attributed to extended defects. Magnetic measurements on SmSi3‐x reveal van Vleck paramagnetic behavior and antiferromagnetic ordering at low temperatures. Computations within the local spin density approximation (LSDA and LSDA+U) on the crystal structure of SmSi3 reproduce the anti­ferro­magnetic coupling as the favored long‐range order. Quantum chemical analysis of the chemical bonding in SmSi3 reveals two‐center two‐electron bonds within the Si2 dumbbells plus a total of a little less than four electrons in lone pairs at each silicon atom.

Capacitive Spectroscopy of Deep Levels in Silicon with Samarium Impurity

The effect of thermal treatment on the behavior of samarium atoms introduced into silicon during the growth process was studied using the method of transient capacitive deep-level spectroscopy (DLTS). It has been shown that various high-temperature treatments lead to the activation of samarium atoms in the bulk of n-Si and the formation of deep levels. The energy spectrum of deep levels arising during heat treatments has been determined. The dependence of the efficiency of formation of these levels in n‑Si<Sm> on the processing temperature has been studied. It was found that the higher the content of samarium atoms in the bulk of silicon at the same high-temperature treatment temperature, the higher the concentration of the deep level EC–0.39 eV. From this, we can conclude that the EC–0.39 eV level is associated with the activation of samarium atoms in the n-Si<Sm> volume.

Enhanced Durable Corrosion Resistance of Samarium-Doped ZnO Solid Solution Materials by 4f Electrons of Samarium Atoms

Enhanced Durable Corrosion Resistance of Samarium-Doped ZnO Solid Solution Materials by 4f Electrons of Samarium Atoms

Laser-induced isotope selective photoionization of atomic samarium

Resonance ionization spectroscopy of samarium has been performed in an atomic beam in conjunction with a time-of-flight mass spectrometer. Isotope selective photoionization studies have been carried out on one of the even isotopes of samarium (152Sm). High degree of isotopic selectivity (> 95%) has been achieved experimentally for 152Sm using multi-mode dye lasers. Isotopic abundance of 152Sm in mass selective photoionization has been studied as a function of excitation laser energy density. By employing isotope selective photoionization spectroscopy, the isotope shifts for the first- and second-step transitions have also been determined.

Additive effect of lanthanide compounds into perovskite layer on photovoltaic properties and electronic structures

Fabrication and characterization of lanthanide compound doped CH3NH3PbI3 (MAPbI3) perovskite solar cells have been performed for improving the photovoltaic properties with long-term stabilities of conversion efficiency. The purpose of this research is to investigate additive effect of formamidinium iodine (FAI) and lanthanide compound into the perovskite layer for improving carrier diffusion and mobility in the perovskite layer. Incorporation of FAI and europium chloride (EuCl2) into the perovskite crystals maintained the stability of conversion efficiency for 30 days. The photovoltaic properties were based on the crystal growth and orientation with suppression of decomposition, thermodynamic stabilities, and the narrow band dispersion with decrease of effective mass. In contrast case, addition of samarium or terbium compound reduced the stabilities, and suppressed the carrier mobility owing to the flat band dispersion of localized d orbital of samarium atom or 4 f orbital of terbium atom near valence band state. The annealing treatment improved the crystal orientation related to the carrier diffusion with inhibiting recombination, improving short circuit current density and external quantum efficiency. The perovskite crystal doped with EuCl2 and FAI have high advantage to apply for practical use of the photovoltaic devices with long-term stability.

Рентгенографические исследования сегнетоэлектрических кристаллов ниобата лития, легированных редкоземельными элементами

The lattice structural distortions of LiNbO3 crystals doped with samarium with a concentration of 1.0, 1.9, 2.5 mol. % were studied by X-ray diffraction methods. It was found that the samarium atoms and some of the niobium atoms occupied the vacant positions of lithium in the crystal lattice, and some of the niobium atoms were located in the empty octahedron. The octahedra of SmLiO6 was distorted more strongly than octahedra of NbLiO6 when niobium atoms entered the vacant positions of lithium. The smallest changes in the bond lengths in the octahedra of the main motif and in the defect region as well as along the polar axis in the lithium niobate lattice were observed in the sample with a samarium concentration of 2.5 mol. %.

From SmOF to SmH0.78OF0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds.

Mixed anionic hydrides of the rare earths are a fascinating class of compounds as potential functional materials, especially in luminescence, as photochromic thin films and for ion conduction. For exploratory studies, the effectiveness of various synthesis methods must be investigated, which is done here for metathesis reactions. The reaction of Sm2O3 with PTFE yields SmOF (P21/c, a = 5.60133(19) Å, b = 5.65567(19) Å, c = 5.6282(2) Å, β = 90.169(5)°, V = 178.295(11) Å3, and Z = 4) in a new, probably metastable, polymorph of the baddeleyite-type structure. Metathesis reactions of SmOF with LiH, NaH, or CaH2 led to a samarium hydride oxide fluoride, SmHxOF1-x; i.e., incomplete H/F exchange occurs. X-ray diffraction and neutron diffraction on a compound with x = 0.78 obtained via NaH reveal hydride, oxide, and fluoride ions to be partially ordered. SmH0.78OF0.22 (Ia3̅, a = 10.947(2) Å, V = 1311.7(4) Å3, Z = 32) crystallizes in an anti-Li3AlN2-type structure with distorted cubic anion coordination for samarium atoms (site symmetry 3̅ and 2) and distorted tetrahedral arrangement of samarium atoms around the anions (site symmetry 1 and 3). It is a fully structurally characterized hydride oxide fluoride and shows a rare crystal chemical feature─the occupation of a crystallographic site by three different anions (0.188 H + 0.667 O + 0.145 F). Interatomic distances between samarium and hydrogen and samarium and the mixed hydrogen/oxygen/fluorine site range from 2.45 to 2.48 Å and 2.29 to 2.42 Å, respectively, and are similar to those in samarium hydride, samarium oxide, and samarium fluoride. Fluoride extraction by reaction with alkali and alkaline earth hydrides has thus proven to be a useful synthesis route to hydride oxides and also hydride oxide halogenides, which might be further exploited in exploratory research on heteroanionic metal hydrides.

Study of the effect of nitrogen and hydrogen on the structure and magnetic properties of (Sm, Er)2Fe17 alloys

Materials based on the Sm2Fe17 compound with nitrogen have great potential for the manufacture of highly efficient permanent magnets. The initial, nitrided, and hydrogenated alloys based on the Sm2Fe17 intermetallic compound with partial substitution of erbium atoms for samarium atoms Sm1.2Er0.8Fe17(H, N)x have been studied by X-ray phase analysis and scanning electron microscopy. Nanopowders of Sm1.2Er0.8Fe17N2 were obtained by mechanical grinding. The grinding time was varied from 0 to 60 minutes. The magnetic hysteresis properties of all powder samples were studied in static magnetic fields up to 7 T, as well as in pulsed magnetic fields up to 60 T. The strength of the intersublattice exchange interaction was estimated. The obtained values λ are valid only for the explored concentration of Sm/Er ions.

Investigations of odd-parity autoionization levels of atomic samarium using three-color resonance ionization spectroscopy

Three-color three-step laser resonance ionization spectroscopy has been employed to investigate the autoionization spectra of atomic samarium in the energy region 50,330 - 51,160 cm−1. The measurements were carried out in an atomic beam coupled to a linear time of flight mass spectrometer. Fifty-five odd-parity autoionization levels of atomic samarium in the above-mentioned energy region have been observed using three excitation schemes. Among these, fifty autoionization levels are new. The total angular momenta of eighteen odd-parity autoionization levels have been assigned uniquely.

Computational Modelling of Ceria-Based Solid Oxide Fuel Cell Electrolyte Materials

The significant advances in materials development for solid oxide fuel cells (SOFCs) and modelling techniques have challenged researchers to develop streamlined methodologies aiming at faster and more reliable fabrication of highly efficient cells. Instead of adopting a trial-and-error technique to discover the optimal composition of fuel cell component materials, alternative tools and techniques should be developed for predicting the likely best compositions in a cost-effective and timely manner. Many formulations have been studied for application as SOFC electrolytes over the years and doubly-doped ceria materials have been of considerable recent interest.Here, a simulation methodology to calculate the lattice parameter and the oxygen ion migration energy of ceria-based electrolyte formulations was developed, and the results were analysed and benchmarked against corresponding results obtained experimentally in order to verify the efficacy of the simulation methodology. To this end, a supercell consisting of 2 x 2 x 2 ceria unit cells doubly-doped with samarium and gadolinium was modelled and simulated using molecular mechanics force field methods using the CP2K computational chemistry suite. Two compositional series were modelled with the general formula Ce32-(x+y)SmxGdyO64-(x+y)/2 where x and y are the number of samarium and gadolinium dopant atoms per supercell respectively. The first compositional series, Series One, had equal amounts of dopants but different total dopant concentration with values of x = y = 1, 2, 8, or 16. Series Two had a fixed total dopant concentration (x + y = 8) but different amounts of each dopant in each structure such that x had integer values from 0 to 8 (x = 0 ... 8) and y = 8 - x. Moreover, two doping strategies were simulated for each compositional series depending on how the dopant atoms and resulting vacancies were distributed throughout the crystal. The first doping strategy places one dopant atom in two or more of the eight minicubes comprising the 2 x 2 x 2 supercell for Series One structures and, for Series Two structures, one dopant atom is placed in each minicube starting with one gadolinium atom in each minicube and then progressively replacing one gadolinium atom with one samarium atom in each of the subsequent structures of this series until there is one samarium atom in each minicube. The second doping strategy places the dopants exclusively in the four minicubes that let the dopants be as far as possible from each other. In all cases, the oxygen vacancies are chosen to be the nearest neighbours, i.e., in the nearest lattice positions, to the dopant atoms.For each structure, the lattice parameter was calculated using a cell optimisation technique utilizing the conjugate gradient method where the soft particle mesh Ewald (SPME) sums method and the DIPole Polarizable Ion Model (DIPPIM) for the long- and short-range potentials respectively. To estimate the activation energies associated with hopping of an oxygen ion from a specific site to a neighbouring site in the structures studied, the following steps were applied: The positions of the dopant atoms in the pure crystal were assigned.The at a distance within 3.0 Å was generated.The climbing image nudged elastic band (CI-NEB) method was applied to determine all the activation barriers of the doped crystal.The average energy barrier was calculated. The results obtained for the lattice parameter were comparable to those observed experimentally and exhibited the same linear trends satisfying Vegard's law, albeit the trend for the fixed dopant concentration series had a slight negative slope. Simulation-derived values of the activation energy showed the same trends as those observed experimentally. The simulations also produced transition state curves showing the saddle point and energy minima for each structure; information that could not be obtained experimentally and that can shed some light on the mechanism of ionic conduction. It was found that the position of oxygen vacancies within the crystal structure play a key role in determining the activation energy of ion hopping, and that the different patterns of doping do not affect the overall trends in lattice parameter and activation energy. They do however produce different patterns in the energy profiles contributing to the energy barriers to ion hopping within the crystal structure.This work demonstrates that computational simulations of SOFC electrolyte materials provide results comparable with those obtained experimentally and could also provide insights into the mechanisms of ionic conduction. The incongruence of the computational and experimental results was attributed to the limitations of the molecular mechanics force field methodology utilised, with the expectation that an ab initio density functional theory (DFT) calculation would yield closer conformance. Figure 1

Polarization Spectra of Even-Parity Highly Excited States of Samarium Atom

Polarization Spectra of Even-Parity Highly Excited States of Samarium Atom

Structural, optical, and luminescence characteristics of Ga1-xSmxP QDs prepared via methylmethacrylates assisted colloidal approach for laser and QLED applications

Semiconductor quantum dots have gained great interest because of their brilliant optical properties because of their size dependent effect which referred as quantum confinement. The proficient confinement of excitons and privation of nonradiative emission are two critical factors for highly luminescent quantum dots production. Here, we report a novel strategy to modulate and tune the emitted light colors from the QD nanocrystals via the doping of the GaP QD with samarium atoms at diverse concentrations. The doping of Sm atoms in the GaP crystal lattice was found to change the size, bandgap and tuning the emitted colors. The XRD disclosed the ability of Sm to expand the GaP cubic crystal lattice. The SEM inspected that the increase of Sm content in GaP instigates an increase of particle size from 3.9 nm to 10.1 nm. The absorption spectrum revealed the decrease of the bandgap from 3.2 eV to 2.65 eV due the increase of Sm concentration. The produced emission spectra exhibited narrow emission bandwidth and highly luminescent quantum yield exceeded 87 %, for the first time for this kind of semiconductor quantum dots. These promising features can enable the Ga1-xSmxP QDs to be served for the laser QDs and QLEDs production.

Enhanced optical absorption of rutile TiO2 through (Sm, C) codoping: a first-principles study

In this Paper, we employ the density functional theory to investigate the electronic and optical properties of rutile TiO $$_2$$ , Sm doped and (Sm, C) co-doped TiO $$_2$$ materials. We use the Tran-Blaha modified Beck Johnson (TB-mBJ) potential. This functional can estimate the band gap of these compounds with more accuracy compared to the generalized gradient approximation (GGA). The obtained electronic band gap of the pristine TiO $$_2$$ is $$E_g = 2.76$$ eV, which is close to the experimental value $$E_g = 3.0$$ eV. We report also that Sm doped and (Sm, C) co-doped TiO $$_2$$ are stable in ferromagnetic state. The magnetic moment of samarium is consistent with other literature works. Furthermore, adding samarium atom with 4f states and carbon atom with activated 2p states improve appreciably the optical properties in the visible light range. The corresponding obtained optical band gap value of the (Sm,C) co-doped TiO $$_2$$ is an optimal one which evidences that the materials is capable of showing high power conversion efficiency. Additionally, the enhancement of optical absorption under the visible-light of these materials, especially the co-doped one can find suitable applications in optoelectronic devices.

The Influence of Milling Modes on the Structure and Magnetic Properties of (Sm, Ho)2Fe17Nx (x = 0, 2.4) Powder Materials

The composition, structure, and surface topology of as-cast, homogenized, and nitrogenized alloy based on an intermetallic compound Sm2Fe17 with partial substitution of samarium atoms with holmium atoms have been studied using X-ray fluorescence and X-ray phase analysis, as well as scanning electron microscopy. Results on the magnetic properties of the initial compound Sm1.2Ho0.8Fe17 and the nitride Sm1.2Но0.8Fe17N2.4 and its milled powders have been presented. It has been found that partial substitution of samarium atoms with holmium ones in a rare-earth metal sublattice in combination with the effect of introducing nitrogen atoms into the initial compound crystal lattice increases such magnetic characteristics as specific magnetization and coercive force. A comparative analysis of the magnetic hysteresis properties of powder samples showed that increasing the duration of the milling of the Sm–Ho–Fe–N powders using high-energy ball milling (15, 30, 45, and 60 min) contributes to improving the main magnetic characteristics. Functional characteristics obtained for Sm–Ho–Fe–N powders after their milling are important for the development of new high-coercivity magnets based on them.

Spectra of Odd-parity Rydberg States of Samarium Atom

Spectra of Odd-parity Rydberg States of Samarium Atom

Investigation of high-lying even-parity levels of atomic samarium with multi-color photoionization technique: Energies and radiative lifetimes

We have investigated high-lying even-parity energy levels of atomic samarium in the energy region 32,156.3–32,886.4 cm−1 using two-color three-step photoionization technique. The experiments have been carried out in an atomic beam coupled to a linear time of flight mass spectrometer. The analysis of the photoionization spectra has resulted in the identification of twenty-five high-lying even-parity energy levels of atomic samarium. These include the confirmation of fifteen energy levels reported earlier while the remaining ten energy levels are new. The observed relative photoionization signal intensities of the corresponding transitions are also reported. The possible total angular momenta of the newly discovered energy levels have been assigned by the total angular momentum selection rules. Further, the radiative lifetimes of twenty high-lying even-parity energy levels of atomic samarium were measured for the first time by delayed three-color three-photon resonance ionization spectroscopy via a pump-probe method.

Three-Photon Resonance Ionization Spectroscopy of Excited Even-Parity States of the Samarium Atom

Excited even-parity states of the samarium atom in the energy interval 32620–34092 cm−1 have been studied by using single-color three-photon resonance ionization spectroscopy. The energies and total angular momenta of 72 states were determined. Nine new levels were revealed.

Radiative lifetimes of even-parity high-lying levels of Sm I by delayed photoionization measurements

Radiative lifetimes of fifteen even-parity high-lying levels of atomic samarium in the energy range 34,000–34,815 cm−1 have been measured systematically. The measurements were carried out by detecting time-resolved delayed three-colour photoionization signal using pump-probe technique in an atomic beam coupled to a time-of-flight mass spectrometer. The measured values are in the range of 35 to 349 ns. Accuracy of the measurements was validated by measuring the lifetime of the first excited level used in the excitation scheme by employing two-colour pump-probe photoionization spectroscopy and comparing the measured value with that reported in the literature.

Aqueous Solvation of SmI3: A Born-Oppenheimer Molecular Dynamics Density Functional Theory Cluster Approach.

We report the results of Born-Oppenheimer molecular dynamics (BOMD) simulations on the aqueous solvation of the SmI3 molecule and of the bare Sm3+ cation at room temperature using the cluster microsolvation approach including 37 and 29 water molecules, respectively. The electronic structure calculations were done using the M062X hybrid exchange-correlation functional in conjunction with the 6-31G** basis sets for oxygen and hydrogen. For the iodine and samarium atoms, the Stuttgart-Köln relativistic effective-core potentials were utilized with their associated valence basis sets. When SmI3 is embedded in the microsolvation environment, we find that substitution of the iodine ions by water molecules around Sm(III) cannot be achieved due to an insufficient number of explicit water molecules to fully solvate the four separate metal and halogen ions. Therefore, we studied the solvation dynamics of the bare Sm3+ cation with a 29-water molecule model cluster. Through the Sm-O radial distribution function and the evolution of the Sm-O distances, the present study yields a very tightly bound first rigid Sm(III) solvation shell from 2.3 to 2.9 Å whose integration leads to a coordination number of 9 water molecules and a second softer solvation sphere from 3.9 to 5 Å with 12 water molecules. No water exchange processes were found. The theoretical EXAFS spectrum is in excellent agreement with the experimental spectrum for Sm(III) in liquid water. The strong differences between the solvation patterns of Sm(III) vs Sm(II) are discussed in detail.