Samarium Atoms Research Articles

Measurement of radiative lifetime in atomic samarium using simultaneous detection of laser-induced fluorescence and photoionization signals

In this paper, we report the investigations of lifetime measurement of odd-parity energy level 19009.52 cm−1 of Sm I using simultaneous detection of laser-induced fluorescence and laser-induced photoionization signals employing pump–probe technique. To the best of our knowledge, this is for the first time that the results obtained using laser-induced fluorescence and photoionization techniques have been compared with each other. The obtained results match well with those reported in the literature.

The Stannides Sm6Pd10–x Sn11 and Sm3Pd5–x

Abstract The stannides Sm6Pd10–x Sn11 and Sm3Pd5–x Sn5 were synthesized from the elements by arc-melting. They were studied by powder and single-crystal X-ray data: C2/m, a = 1720.45(10), b = 451.97(2), c = 1420.60(8), β = 99.705(5)°, wR2 = 0.086, 2076 F 2 values, 83 variables for Sm3Pd4.95(1)Sn5 and C2/m, a = 1738.68(7), b = 451.49(1), c = 1692.68(7), β = 121.375(3)°, wR2 = 0.0335, 2164 F 2 values, 85 variables for Sm6Pd9.82(1)Sn11. Both structures show small defects for one palladium site. The palladium and tin atoms in Sm6Pd10–x Sn11 and Sm3Pd5–x Sn5 build up complex three-dimensional polyanionic networks in which the samarium atoms fill cavities within distorted pentagonal channels. In addition to strong covalent Pd–Sn bonding, the polyanions are further stabilized by Pd–Pd and Sn–Sn bonding.

Effect of deposition of samarium atoms on the electron-stimulated desorption of cesium and samarium atoms from the surface of tungsten coated by gold and cesium

It has been shown that deposition of Sm atoms on W(100) surface coated by several monolayers of gold and cesium affects noticeably the yield of Cs atoms in electron-stimulated desorption (ESD) from this surface. The measurements have been performed by the time-of-flight method with a surface-ionization detector. The paper reports on the first observation of ESD of Sm atoms from the tungsten surface coated by layers of gold and cesium. The ESD threshold for Sm atoms, E e = 57 eV, coincides with that for Cs atoms and corresponds to the energy of the Au 5p 3/2 core level. The dependence of the ESD yield of Sm atoms on the bombarding electron energy E e follows a resonance pattern in the form of a narrow peak located in the range 57 ≤ E e ≤ 66 eV. Deposition of Sm atoms at room temperature (∼300 K) reduces (by a factor of about two) the ESD yield of Cs atoms for 600 s, and deposition of Sm atoms at 160 K reduces the ESD of Cs atoms down to zero already for 270 s. This difference finds explanation in the study of the change the structure of the top layer of the (Au + Cs)/W surface coating undergoes under cooling of the surface from 300 to 160 K.

Enhancement of the single-colour three-photon resonance spectroscopy of highly excited states of the samarium atom

Enhancement of the single-colour three-photon resonance spectroscopy of highly excited states of the samarium atom

Application of electron-stimulated desorption for studying adsorbed layers

After a brief discussion of the main result of the research initiated by N.I. Ionov in his laboratory using electron-stimulated desorption for studying the surface layers of tungsten, we consider in greater detail recent results on layered coatings formed on the tungsten surface upon simultaneous adsorption of sodium (or cesium) and gold atoms on this surface, as well as the effect of sputtering of samarium atoms on the (Cs + Au)/W(100) surface that has already been formed at 300 K.

The effect of field strength on the resonance structure of three-photon ionization spectra of the samarium atom

Amplitude ratios of resonance maxima caused by two-photon transitions from different levels of the ground term of the samarium atom are studied experimentally and theoretically as functions of the laser-radiation field strength. The results of these studies are shown to be promising for identifying the resonance structure of three-photon ionization spectra of the samarium atom. A not yet observed excited even-parity state with energy E ≈ 36789.1 cm−1 and hypothetical values of total angular momentum J = 5, 6 has been discovered.

Transport properties of Cu5SmSe4

The electrical conductivity, Hall coefficient, thermoelectric power, and thermal conductivity of Cu5SmSe4 have been measured at temperatures from 80 to 400 K, and its linear thermal expansion coefficient has been determined from X-ray diffraction data. The observed negative a-axis linear thermal expansion coefficient and anomalies in temperature-dependent transport properties of this compound are tentatively attributed to a transition of the samarium atoms from a divalent to a trivalent state.

Increase in thermoelectric figure of merit in Sm x Pb1−x Te solid solutions through substitution of lead atoms by samarium atoms

On the basis of temperature relationships of electric conduction (σ), thermo-emf (α), heat conduction (K tot), thermoelectric power α 2 σ and figure of merit Z in Sm x Pb1−x Te solid solutions are calculated. It has been shown that the growth in the number of samarium atoms, which replace lead atoms, leads to an increase in Z. It has been found out that relatively high values of Z in Sm x Pb1−x Te solid solutions as compared to PbTe are mainly due to scattering of phonons and holes on defects as well as due to an increase in an effective mass in them during substitution of lead by samarium.

Access to an Unexplored Chiral C82 Cage by Encaging a Divalent Metal: Structural Elucidation and Electrochemical Studies of Sm@C2(5)‐C82

Access to a chiral C(82) cage: Encaging a divalent samarium atom has provided access to an unexplored chiral cage of C(2)(5)-C(82) that has never been reported for trivalent M@C(82) or empty fullerenes. Inside this cage, a wandering Sm atom has been identified using crystallographic methods. In addition, electrochemical studies of Sm@C(2)(5)-C(82) have been performed to explore its oxidation properties (see figure).

Investigation of highly excited states of samarium

Highly excited even-parity states of the samarium atom in the range between 34104 and 39155 cm−1 have been studied by the method of one-color three-photon resonance ionization spectroscopy. The energies and total angular momenta of 342 states have been determined. Seven new even-parity states of samarium have been discovered.

Large Endohedral Fullerenes Containing Two Metal Ions, Sm2@D2(35)-C88, Sm2@C1(21)-C90, and Sm2@D3(85)-C92, and Their Relationship to Endohedral Fullerenes Containing Two Gadolinium Ions

The carbon soot obtained by electric arc vaporization of carbon rods doped with Sm(2)O(3) contains a series of monometallic endohedral fullerenes, Sm@C(2n), along with smaller quantities of the dimetallic endohedrals Sm(2)@C(2n) with n = 44, 45, 46, and the previously described Sm(2)@D(3d)(822)-C(104). The compounds Sm(2)@C(2n) with n = 44, 45, 46 were purified by high pressure liquid chromatography on several different columns. For endohedral fullerenes that contain two metal atoms, there are two structural possibilities: a normal dimetallofullerene, M(2)@C(2n), or a metal carbide, M(2)(μ-C(2))@C(2n-2). For structural analysis, the individual Sm(2)@C(2n) endohedral fullerenes were cocrystallized with Ni(octaethylporphyrin), and the products were examined by single-crystal X-ray diffraction. These data identified the three new endohedrals as normal dimetallofullerenes and not as carbides: Sm(2)@D(2)(35)-C(88), Sm(2)@C(1)(21)-C(90), and Sm(2)@D(3)(85)-C(92). All four of the known Sm(2)@C(2n) endohedral fullerenes have cages that obey the isolated pentagon rule (IPR). As the cage size expands in this series, so do the distances between the variously disordered samarium atoms. Since the UV/vis/NIR spectra of Sm(2)@D(2)(35)-C(88) and Sm(2)@C(1)(21)-C(90) are very similar to those of Gd(2)C(90) and Gd(2)C(92), we conclude that Gd(2)C(90) and Gd(2)C(92) are the carbides Gd(2)(μ-C(2))@D(2)(35)-C(88) and Gd(2)(μ-C(2))@C(1)(21)-C(90), respectively.

Heterobimetallic Samarium(III) and Titanium(IV) Complexes with Bifunctional Catalytic Properties

Reaction of the bis-ligand-chelated samarium complex [Sm(Hbptd)(H2bptd)] (1; H3bptd =1,9-bis(2-pyrrolyl)-2,5,8-triazanona-1,8-diene), in which a pyrrolyl ring is dangling and metal-free, with Ti(NMe2)4 yielded the heterometallic complex [Sm(Hbptd)(THF)(bptd)Ti(NMe2)2] (2). Treatment of the H3bptd ligand with 1 equiv of Ti(NMe2)4 gave the titanium amido complex [Ti(bptd)(NMe2)] (3). Complexes 2 and 3 were able to catalyze the hydroamination of phenylacetylene with 2,4-dichloroaniline and 4-methoxyaniline, and high regioselectivities were observed for the two amines. Both 1 and 2 were active catalysts for the ring-opening polymerization of ε-caprolactone. 2 showed higher activity for the polymerization reactions, due to a decrease in the coordination number of the samarium atom (from 9 in 1 to 8 in 2) by sharing its ligand with the titanium center.

Y2BaCuO5 buffer block as a diffusion barrier for samarium in top seeded melt growth processedYBa2Cu3O7 − y superconductorsusing a SmBa2Cu3O7 − d seed

A Y2BaCuO5 buffer(Y211) block, as a diffusion barrier for samarium atoms of a top seeded melt growth (TSMG) processedYBa2Cu3O7 − y (Y123) superconductorusing a SmBa2Cu3O7 − d (Sm123) seed, was examined in terms of the buffer thickness (t). Disc-type Y211blocks with various t were inserted at the seed/compact interface and subjected to meltgrowth heating cycles. The superconducting transition temperature (Tc) and criticalcurrent density (Jc) were measured for the three different top surface regions: (1) the region justbelow the seeded Y211 buffer block, (2) the intermediate region betweenthe buffer block and the sample edge, and (3) the sample edge. TheTc values of regions 1 and 2 of the samples without the buffer and with thin buffers were lowerthan that of region 3, and the superconducting transition widths were larger. Ast was increased to 3 mm, the susceptibility curves of the three regions showed the sameTc of 90 K and sharptransitions. The Jc–B curves of regions 1 and 2 without a buffer and with thin buffers showed the peak effect due to the formation ofY1 − xSmxBa2Cu3Oz. The peak effect almostdisappeared when t was increased to 3 mm. Y211 particles and the Y123 matrix in the buffer block acted asan effective samarium absorber by forming mixed rare-earth 211 particles andY1 − xSmxBa2Cu3Oy. These results suggest that the Y211 buffer block technique can be applied tothe fabrication of large single grain Y123 superconductors with a uniformTc andJc distribution on the top surfaces.

Measurement of total angular momentum values of high-lying even-parity atomic states of samarium by spectrally resolved laser-induced fluorescence technique

Spectrally resolved laser-induced fluorescence technique was used to uniquely assign total angular momentum (J) values to high-lying even-parity energy levels of atomic samarium. Unique J value assignment was done for seven energy levels in the energy region 34,800–36,200 cm−1, recently observed and reported in the literature.

Formation of ferroelectric single-crystal architectures in LaBGeO 5 glass by femtosecond vs. continuous-wave lasers

We have succeeded in crystallizing LaBGeO 5 glass with an 800 nm, 250 kHz repetition rate femtosecond laser and observed different crystallization behavior when varying focal depth. Despite glass and crystal having the same composition, an unidentified off-stoichiometric phase appeared before crystalline LaBGeO 5 when focusing deep inside the glass. Crystal lines were written in three dimensions inside the glass, and the results were compared to 1064 nm continuous-wave laser crystallization of Sm-doped LaBGeO 5 by samarium atom heat processing. Notable differences were found in the structure of the lines and crystal growth rates, with femtosecond laser crystallization requiring much higher writing speeds. Raman spectra were highly consistent, suggesting that the lines were highly oriented with a consistent alignment between the crystal lattice and the growth direction.

Crystal structure of the metal-rich phosphide Sm15Ir33P26

Abstract The new metal-rich phosphide Sm15Ir33P26 was obtained from a reaction of the elements in a lead flux (1 : 2 : 2 : 30 molar ratio, 1370 K, slow cooling rate). Sm15Ir33P26 adopts a new structure type which was characterized by powder and single crystal X-ray data: C2/m, a = 4720.6(8), b = 392.87(9), c = 1329.2(2) pm, β = 95.478(1)°, wR2 = 0.0376, 3757 F 2 values and 227 variables. The iridium and phosphorus atoms build up a complex three-dimensional [Ir33P26] δ– polyanionic network in which the samarium atoms fill diverse larger cavities with coordination numbers of 15–17. The seventeen crystallographically independent iridium atoms have between 3 or 4 phosphorus neighbors in distorted trigonal-, square-planar, or tetrahedral coordination. All phosphorus atoms are isolated and most of them fill tri-capped trigonal prisms. The Sm15Ir33P26 structure is an intergrowth variant of ThCr2Si2, SrPtSb, CeMg2Si2, and TiNiSi-related slabs.

Diffusion of samarium into iridium from an incident flux of samarium atoms onto iridium coated with a graphite monolayer

A study by the method of thermal-desorption spectroscopy has revealed an effective diffusion of Sm atoms into Ir(111), which is stimulated by a graphite monolayer on the iridium surface. It is shown that the diffusion efficiency is greater by a factor of ∼106–107 in the presence of a graphite monolayer on iridium than in the absence of this layer. The energy of activation for the diffusion of Sm atoms into and from iridium has been found to be E = 5.5 eV and E = 6.3 eV, respectively. Iridium strips with a samarium-saturated nearsurface layer can be used as efficient sources of Sm ions (or Sm atoms), with the flux density varying in the range of 4 × 109 cm−2 s−1 〈 ν 〈 3 × 1011 cm−2 s−1 as the temperature of the strip varied from 1830 to 2110 K. If the temperature of the strip remains unchanged, the flux of Sm is maintained constant for many hours. After contact with the ambient atmosphere and evacuation of air, the samarium-saturated iridium strip is still serviceable as a source of samarium.

Double resonances upon three-photon ionization of the samarium atom

The manifestation of double resonances upon the three-photon ionization of the samarium atom has been studied in a frequency range of 17200–18400 cm−1. Thirty peaks caused by double resonances have been found in the dependence of the yield of Sm+ ions on the laser radiation frequency. The majority of these peaks greatly exceed in amplitude the peaks associated with ordinary two-photon resonances. The influence of double resonances on the three-photon ionization has been theoretically analyzed using the density matrix approximation. The calculations show that the probability of the three-photon resonance ionization can increase by more than two orders of magnitude due to the additional one-photon population of an intermediate level. The double resonance slows down the rate of increase in the probability of ionization with an increase in the laser radiation intensity compared to ordinary two-photon resonance.

Coadsorption of samarium with oxygen on the molybdenum (2 1 1) surface

Samarium atoms exist in two different electronic configurations, namely, divalent (Sm 2+) and trivalent (Sm 3+). Up to now, those two electronic configurations have been connected with the existence of Sm atoms in different valence states. Recent theoretical calculations performed by Yakovkin [9] show that both electronic configurations have similar LDOS around the Fermi level, and as a result, should give a similar photoelectron emission in the valence band region, which was identified earlier as the emission from the Sm 2+ state. The Sm 3+ signal in photoelectron emission could originate from contaminations of Sm by other elements, e.g. oxygen. To check the influence of O on the electronic structure of Sm, the XPS experiments of coadsorption of O and Sm have been performed.

Measurements of radiative lifetimes, branching fractions, and absolute transition probabilities in atomic samarium using laser-induced fluorescence

We report the simultaneous measurements of radiative lifetimes, branching fractions, and absolute transition probabilities in atomic samarium using laser-induced fluorescence. The radiative lifetimes of seven odd-parity energy levels and six step-wise-excited even parity energy levels of atomic samarium have been measured. The lifetime values of odd-parity energy levels agree well with those reported in the literature, and the values of even-parity energy levels are new. Excited-level-to-ground-level branching fractions and absolute transition probabilities for twenty-one transitions in atomic samarium are measured using single-color laser-induced fluorescence, and the results are compared against the values reported in the literature. We also report branching fractions and absolute transition probabilities for fifty-one excited-level-to-excited-level transitions in atomic samarium using two-color laser-induced fluorescence. The existing ambiguity in assigning the total angular momentum values for the six stepwise-excited even-parity energy levels is removed by assigning each of these excited levels a unique J value by identifying known odd-parity lower levels to which a stepwise-excited even-parity level decays via fluorescence decay channels.