Doublet Structure Research Articles

Effects of the atomic environment on the electron binding energies in samarium

Effects of the atomic environment on the L1, L2, L3, M1, M2, M3, and N1 electron binding energies in samarium generated in the electron capture decay of radioactive 149Eu were investigated by means of the internal conversion electron spectroscopy using the conversion electron spectrum of the 22.5keV M1+E2 nuclear transition in the daughter 149Sm. In this investigation, four pairs of 149Eu sources prepared by vacuum evaporation deposition and by ion implantation at 30keV with the use of four different source backing materials, namely polycrystalline carbon, aluminium, gadolinium and platinum foils, were employed. The greatest average difference of (3.1±0.1)eV in the L1, L2, L3, and M1 subshell electron binding energies was observed between the 149Eu sources prepared by ion implantation into the aluminium and platinum substrates. On the other hand, minimal differences in the electron binding energies were generally found between samarium generated in the evaporated layer and in the bulk for the individual investigated source backings with the exception of the gadolinium foil. A doublet structure of all investigated conversion electron lines with the average values of 8.1±0.2eV and 1.5±0.1 for the separation energy and the intensity ratio of the low-energy to high-energy components, respectively, was observed for the 149Eu sources prepared by ion implantation into the aluminium and carbon foils. This structure was presumably caused by the presence of both the trivalent and divalent Sm ions in the sources. No significant differences in natural widths of the L1, L2, L3, M1, M2, and M3 samarium atomic levels among the investigated matrices were observed with the exception of the source prepared by the implantation of the 149Eu ions into the platinum foil for which the determined values for all investigated subshells were apparently higher.

Structural basis of the Inv compartment and ciliary abnormalities in Inv/nphp2 mutant mice.

The primary cilium is a hair like structure protruding from most mammalian cells. The basic design of the primary cilium consists of a nine microtubule doublet structure (the axoneme). The Inv compartment, a distinct proximal segment of the ciliary body, is defined as the region in which the Inv protein is localized. Inv gene is a responsible gene for human nephronophthisis type2 (NPHP2). Here, we show that renal cilia have a short proximal microtubule doublet region and a long distal microtubule singlet region. The length of the Inv compartment was similar to that of the microtubule doublet region, suggesting a possibility that the doublet region is the structural basis of the Inv compartment. Respiratory cilia of inv mouse mutants had ciliary rootlet malformation and showed reduced ciliary beating frequency and ciliary beating angle, which may explain recurrent bronchitis in NPHP2 patients. In multiciliated tracheal cells, most Inv proteins were retained in the basal body and did not accumulate in the Inv compartment. These results suggest that the machinery to transport and retain Inv in cilia is different between renal and tracheal cilia and that Inv may function in the basal body of tracheal cells.

Error tolerance studies for the superconducting linac of RAON

RAON, an ion accelerator, is planned in Daejeon, Korea, by the Rare Isotope Science Project. RAON has three linear accelerators, and they will accelerate various stable ions such as uranium, xenon, oxygen and rare isotopes from the isotopes separation on-line system. The linear accelerators of the RAON adopted superconducting cavities and a warm quadrupole doublet structure. Because the target beam power is 400 kWfor the uranium beam, the small beam loss in the linear accelerators can be concluded to the radiation damage to the devices in this region. As a result, estimating the allowable alignment and radio-frequency errors for the RAON linear accelerator is one of the important topics for this project. In this paper, the beam dynamics simulation results, including such errors, will be described.

Strongly driven nonlinear quantum optics in microring resonators

We present a detailed analysis of strongly driven spontaneous four-wave mixing in a lossy integrated microring resonator side-coupled to a channel waveguide. A nonperturbative, analytic solution within the undepleted pump approximation is developed for a cw pump input of arbitrary intensity. In the strongly driven regime self- and cross-phase modulation, as well as multi-pair generation, lead to a rich variety of power-dependent effects; the results are markedly different than in the low power limit. The photon pair generation rate, single photon spectrum, and joint spectral intensity (JSI) distribution are calculated. Splitting of the generated single photon spectrum into a doublet structure associated with both pump detuning and cross-phase modulation is predicted, as well as substantial narrowing of the generated signal and idler bandwidths associated with the onset of optical parametric oscillation at intermediate powers. Both the correlated and uncorrelated contributions to the JSI are calculated, and for sufficient powers the uncorrelated part of the JSI is found to form a quadruplet structure. The pump detuning is found to play a crucial role in all of these phenomena, and a critical detuning is identified which divides the system behaviour into distinct regimes, as well as an optimal detuning strategy which preserves many of the low-power characteristics of the generated photons for arbitrary input power.

On the luminescence of freshly introduced a-screw dislocations in low-resistance GaN

Using scanning electron microscopy in the cathodoluminescence mode, it is shown that straight segments of a-screw dislocations introduced by plastic deformation at room temperature into unintentionally doped low-resistance gallium nitride luminesce in the spectral range 3.1–3.2 eV at 70 K. The spectral composition of dislocation luminescence shows a fine doublet structure with a component width of ∼15 meV and splitting of ∼30 meV, accompanied by LO-phonon replicas. Luminescent screw dislocations move upon exposure to an electron beam and at low temperatures, but retain immobility for a long time without external excitation. Optical transitions involving the quantum-well states of a stacking fault in a split-dislocation core are considered to be the most probable mechanism of the observed phenomenon.

Is the pentaquark doublet a hadronic molecule?

A recently announced discovery by LHCb of a doublet of overlapping pentaquark resonances poses a question of what can be the origin of this doublet structure. We attract attention to the fact that such degeneracy could naturally arise if constituent "baryon" and "meson" were in the colored rather than colorless states. This is an appealing possibility, also because in such a case the pentaquark state would be no less "elementary" than the other hadrons, and would provide a chance for essentially new non-Abelian chemistry.

Transmission‐type negative group delay networks using coupled line doublet structure

This study presents a novel approach to the design and implementation of transmission-type negative group delay (NGD) networks based on a coupled line doublet structure. To improve the reflection coefficients, a quarter-wavelength transmission line is connected between the input and through ports of a coupled line section. For the doublet structure, two coupled line sections are arranged in a symmetrical manner by connecting them back-to-back with the help of the quarter- wavelength through line. For the experimental demonstration, two planar NGD networks (unmatched and matched doublet NGD networks) are designed, simulated and measured at a centre frequency of 2.14 GHz. From the measurement, a group delay (GD) of −5.66 ns and signal attenuation (SA) of 18.78 dB were obtained in the case of an unmatched NGD network. Similarly, for the matched NGD case, a GD of −6.33 ns, SA of 20.69 dB and input/output return losses >29 dB were obtained at the centre frequency.

High-Resolution Millimeter Wave Spectroscopy and Ab Initio Calculations of Aminomalononitrile

The HCN trimer aminomalononitrile (H2NCH(CN)2, AMN) is considered as a key compound in prebiotic chemistry and a potential candidate for detection in the interstellar medium. In this view, we studied the rotational spectrum of AMN in the 120-245 GHz frequency range. The spectroscopic work was augmented by high-level ab initio calculations. The calculations showed that between two existing rotamers, symmetric and asymmetric, the most stable is the asymmetric conformation, and it is the only conformation observed in the recorded spectra. The symmetric conformation is 6.7 kJ/mol higher in energy and thus has a very low Boltzmann factor. The analysis of the rotational spectra of the A conformation has shown that the observed lines exhibit a doublet or quartet structure owing to two large-amplitude motions, C-N torsion and amino group inversion. To study the large-amplitude motions in detail, we calculated a two-dimensional potential energy surface and determined the barrier heights for the torsion and inversion, Vt = 12.5 kJ/mol and Vi = 19.1 kJ/mol. About 2500 assigned rotational transitions in the ground vibrational state were fitted within experimental accuracy using the reduced axes system Hamiltonian. The set of obtained spectroscopic parameters allows accurate calculation of transition frequencies and intensities for an astrophysical search of AMN.

Thallium and manganese complexes involved in the luminescence emission of potassium-bearing aluminosilicates

The luminescence emission at 285nm in natural K-feldspar has been studied by Russian groups and associated with thallium ions in structural positions of K+ sites as artificially thallium-doped feldspars display the same emission band. Here attention is focussed on spectra of CL emission bands centered near 285 and 560nm from paragenetic adularia, moscovite and quartz micro-inclusions. With accesorial thallium they show clear resemblances to each other. Associated sedimentary and hydrothermal aluminosilicate samples collected from Guadalix (Madrid, Spain) were analyzed with a wide range of experimental techniques including Environmental Scanning Electron Microscopy (ESEM) with an attached X-Ray Energy-Dispersive Spectrometer (EDS) and a cathodoluminescence probe (CL) and Electron Probe Microanalysis (EPMA), X-Ray Fluorescence Spectrometry (XRF), Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), Differential and Thermogravimetric Analyses (DTA-TG), radioluminescence (RL), Mössbauer spectroscopy and X-Ray Photoelectron Spectrometry (XPS). The luminescence emission bands at 285 and 560nm seem to be associated with hydrous thallium–manganese complexes bonded to potassium-bearing aluminosilicates since various minerals such as K-feldspar, moscovite and quartz micro-inclusions display similar CL spectra, accesorial thallium and hydroxyl groups. The presence of iron introduces a brown color which is attributed to submicroscopic iron oxides detectable in the optical and chemical microanalysis, but this does not contribute to the luminescence emission. The XPS Mn 2p spectrum of the adularia sample at room temperature is composed of a spin–orbit doublet plus clear shake-up satellite structure ~4eV above the main photoemision lines and is consistent with Mn2+ in good agreement with the observed luminescence emission at 560nm for aluminosilicates produced by a 4T1(4G)→6A1(6S) transition in tetrahedrally coordinated Mn2+. Moscovite samples display spectral CL bands at 285 and 560nm but only when the electron-beam is directed along the (010) orientation and not along the (001) orientation. The Tl+ versus K+ cation isomorphism anchors the luminogenous hydrous thallium–manganese complexes to the potassium-bearing aluminosilicate surfaces under analyses. The CL emission bands at 285 and 560nm of these complexes together with the EDS detection of thallium are a fast analytical measurement detecting the presence of thallium in further studies involving this toxic element.

Optical properties of large-area ultrathin MoS2 films: Evolution from a single layer to multilayers

We investigated the optical properties of ultrathin MoS2 films (number of layers: N = 1, 2, 4, and 12) using Raman spectroscopy, photoluminescence (PL) spectroscopy, and spectroscopic ellipsometry. We estimated the layer thicknesses based on Raman spectra. We characterized the microstructural properties of a single-layer MoS2 film using atomic force microscopy. We measured the lowest-energy A and B excitons using PL spectroscopy. We measured the ellipsometric angles (Ψ and Δ) of MoS2 thin films using spectroscopic ellipsometry, and obtained the dielectric functions as the films' thickness changed from a single layer to multi-layers. We determined the films' optical gap energies from the absorption coefficients. Applying the standard critical point model to the second derivative of the dielectric function (d2ε(E)/dE2), we determined several critical point energies. The d2ε(E)/dE2 spectra showed doublet peaks around 3 eV corresponding to the C and D transitions, as well as doublet peaks around 2 eV corresponding to the A and B transitions. These doublet structures at 3 eV are attributed to the transitions in the Brillouin zone between the Γ and K points.

Raman spectroscopy of albumin interaction with nanodiamond films

This study is focused on finding the possible structural changes of molecules of one of the principal proteins of blood plasma (albumin) that occur upon their interaction with nanodiamonds. The interaction between nanodiamond films and protein films that form after solutions dry up is analyzed. A possibility of spontaneous protein crystallization after the solution dries up on the surface of a nanodiamond film is demonstrated. It is found by means Raman spectroscopy that the secondary structure, the structure of disulfide bridges, and the structure of the tyrosine doublet of the protein do not change (with respect to the corresponding structures in the lyophilized state) upon the interaction of the protein with a nanodiamond film, at least in the bulk of a protein film with a thickness of 1 μm. However, conformational changes may occur in a fairly thin (about 20 nm) near-surface layer of the protein film.

Electronic structure of open-shell tetrahedral {Fe(NO)2}(9) dinitrosyliron complexes.

High-level ab initio excited-state theory is employed to investigate the electronic structure of doublet {Fe(NO)2}(9) species in the ground state and compared with the results obtained by density functional theory. Both of the approaches consistently suggest that the linear NO ligands in dinitrosyliron complexes (DNICs) feature a radical character. Theoretical calculations also predict that the cyanide-supported DNIC anion of [(NC)2Fe(NO)2](-) features C2v symmetry with a Fe-C-N bonding motif, and multireference theories suggest a minimal active space of CAS(9,9) to describe these {Fe(NO)2}(9) compounds, while larger CAS(13,13) calculations do not tend to significantly improve the geometries. Experimental vibration modes of NO ligands are also accurately assigned due to second-order n-electron valence state perturbation theory.

Some recent experimental results related to nuclear chirality

Detailed band structures of three chiral-candidate nuclei, 134Pr, 132La and 103Rh have been studied. The aim of the study was twofold. First, to try to explore the reasons behind the contradiction between the theoretically predicted chirality in these nuclei and the recently observed fingerprints that suggest non-chiral interpretation for the previous chiral candidate band doublets. Second, to search for multiple chiral bands of different types in these nuclei. In 134Pr a new πh11/2vh11/2 band has been observed besides the previously known chiral-candidate πh11/2vh11/2 doublet. This new band and the yrare πh11/2vh11/2 band show the expected features of a chiral doublet structure. This fact combined with the observed similarity between the band structures of 134Pr and 132La suggests that chirality might exist in these nuclei. The detailed study of the 103Rh band structure resulted in the observation of two new chiral-doublet looking structures besides the previously known one. This is indicative of possible existence of multiple chiral doublet structure in this nucleus.

Fine structure of silicoflagellate double skeletons

Abstract Silicoflagellate double skeletons are commonly considered to be pre-division stages, even though their life cycle is only partially resolved, especially with respect to reproduction. Double skeletons of the modern silicoflagellate genera Dictyocha Ehrenberg, Distephanus Stohr, and Octactis Schiller are for the first time examined in detail by scanning electron microscopy in order to improve our understanding of how skeletal morphology relates to paired skeletons. A number of genus-specific mechanisms enable sibling skeletons to be held together at their abbasal surfaces, including a zig-zag design of the basal ring achieved via apical structure, strut attachment and pike rotation (in Distephanus and Dictyocha), and the presence of organic material binding the generally planar basal rings (in Octactis). Contrary to what is generally understood, the siblings are not mirror images of one another. Instead, the triple junctions formed by the skeletal elements of each apical structure are transposed across the middle of the dividing cell to produce a copy with the same rotation. Thus, two dome-shaped skeletons represent halves of a more spherical design, which suggests that the role of the silicoflagellate basal ring is to enable double skeleton formation, but the full implications of this have yet to be explored. Although the purpose of double skeleton formation in silicoflagellates remains unclear, observations from the fossil record indicate that differences in the relative alignment of doublet members can have a high significance for phylogeny. Differences in the doublet structure of living silicoflagellates call for a combined biological and geological perspective of the utility of maintaining Dictyocha, Distephanus and Octactis as separate genera.

Zeeman interaction in ThOH3Δ1for the electron electric-dipole-moment search

The current limit on the electron's electric dipole moment, $|{d}_{e}|<8.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}29}$ $e\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ (90% confidence), was set using the molecule thorium monoxide (ThO) in the $J=1$ rotational level of its $H{\phantom{\rule{0.16em}{0ex}}}^{3}{\ensuremath{\Delta}}_{1}$ electronic state [J. Baron et al., Science 343, 269 (2014)]. This state in ThO is very robust against systematic errors related to magnetic fields or geometric phases, due in part to its $\ensuremath{\Omega}$-doublet structure. These systematics can be further suppressed by operating the experiment under conditions where the $g$-factor difference between the $\ensuremath{\Omega}$ doublets is minimized. We consider the $g$ factors of the ThO $H{\phantom{\rule{0.16em}{0ex}}}^{3}{\ensuremath{\Delta}}_{1}$ state both experimentally and theoretically, including dependence on $\ensuremath{\Omega}$ doublets, the rotational level, and the external electric field. The calculated and measured values are in good agreement. We find that the $g$-factor difference between $\ensuremath{\Omega}$ doublets is smaller in $J=2$ than in $J=1$ and reaches zero at an experimentally accessible electric field. This means that the $H,J=2$ state should be even more robust against a number of systematic errors compared to $H,J=1$.

Study of the confined states in AlxGa1−xAs/GaAs/vacuum surface quantum well

In this paper, we investigate the optical properties of confined electronic states in ultra-thin Al0.27Ga0.73As/GaAs/vacuum surface quantum wells by using photoreflectance spectroscopy at room temperature. Well-resolved doublet structures were found in the spectra. The energy of the features increases with decreasing well width in agreement with the predictions of a model of the transition energy between confined electron and hole states in a surface quantum well. Both the transition broadening and intensity behaviors are also well explained by the effective mass approximation theory. The offset between the un-perturbed theoretical transition energy and the experimental data has been explained by surface-state interaction effects. Moreover, the fact that the light hole ground state in the surface quantum well can be pushed out from the surface quantum well has been directly observed experimentally.

Synthetic and natural chromium-bearing spinels: an optical spectroscopy study

Four samples of synthetic chromium-bearing spinels of (Mg, Fe2+)(Cr, Fe3+)2O4 composition and four samples of natural spinels of predominantly (Mg, Fe2+)(Al, Cr)2O4 composition were studied at ambient conditions by means of optical absorption spectroscopy. Synthetic end-member MgCr2O4 spinel was also studied at pressures up to ca. 10 GPa. In both synthetic and natural samples, chromium is present predominantly as octahedral Cr3+ seen in the spectra as two broad intense absorption bands in the visible range caused by the electronic spin-allowed 4A2g → 4T2g and 4A2g → 4T1g transitions (U- and Y-band, respectively). A distinct doublet structure of the Y-band in both synthetic and natural spinels is related to trigonal distortion of the octahedral site in the spinel structure. A small, if any, splitting of the U-band can only be resolved at curve-fitting analysis. In all synthetic high-chromium spinels, a couple of relatively narrow and weak bands of the spin-allowed transitions 4A2g → 2Eg and 4A2g → 2T1g of Cr3+, intensified by exchange-coupled interaction between Cr3+ and Fe3+ at neighboring octahedral sites of the structure, appear at ~14,400 and ~15,100 cm−1. A vague broad band in the range from ca. 15,000 to 12,000 cm−1 in synthetic spinels is tentatively attributed to IVCr2+ + VICr3+ → IVCr3+ + VICr2+ intervalence charge-transfer transition. Iron, mainly as octahedral Fe3+, causes intense high-energy absorption edge in near UV-range (ligand–metal charge-transfer O2− → Fe3+, Fe2+ transitions). As tetrahedral Fe2+, it appears as a strong infrared absorption band at around 4,850 cm−1 caused by electronic spin-allowed 5E → 5T2 transitions of IVFe2+. From the composition shift of the U-band in natural and synthetic MgCr2O4 spinels, the coefficient of local structural relaxation around Cr3+ in spinel MgAl2O4–MgCr2O4 system was evaluated as ~0.56(4), one of the lowest among (Al, Cr)O6 polyhedra known so far. The octahedral modulus of Cr3+ in MgCr2O4, derived from pressure-induced shift of the U-band of Cr3+, is ~313 (50) GPa, which is nearly the same as in natural low-chromium Mg, Al-spinel reported by Langer et al. (1997). Calculated from the results of the curve-fitting analysis, the Racah parameter B of Cr3+ in natural and synthetic MgCr2O4 spinels indicates that Cr–O-bonding in octahedral sites of MgCr2O4 has more covalent character than in the diluted natural samples. Within the uncertainty of determination in synthetic MgAl2O4 spinel, B does not much depend on pressure.

Low-Temperature Electron Spectra of Impurities in Naphtalene Crystals

This work relates to the study of vibrational structures in the electron spectra of naphthalene crystals with impurities of b- and a-naphthalene fluorine with concentrations of 10^−4 to 10 wt.% at a temperature at 4.2 K. It is determined that, at low impurity concentrations, the spectra have a doublet structure and consist of narrow quasilines with initial values of v01 = 31322 cm^−1 and v02 = 31226 cm^−1, which are resonance-coincident in the absorption and fluorescence spectra. It is demonstrated that if the impurity concentration increases, the series of narrow quasilines appear in the areas of the 0-0 transitions of the impurity centers of both types together with the doublet structure. A part of these quasilines is polarized predominantly along the b-axis of a naphthalene crystal. The model is proposed for impurity centers, which induce the generation of new spectral bands. This model is based on the interaction of translation-nonequivalent impurity molecules in the elementary lattice cell of a naphthalene crystal. At high impurity concentrations, the resonance-symmetric wide spectral bands appear in the absorption and fluorescence spectra. The analysis of the results obtained is performed with consideration for the Franck–Condon interaction and the Herzberg–Teller interaction.

The geology of the Målingen structure: A probable doublet to the Lockne marine‐target impact crater, central Sweden

AbstractThe Målingen structure is an approximately 700 m wide, rimmed, sediment‐filled, circular depression in Precambrian crystalline basement approximately 16.2 km from the concentric, marine‐target Lockne crater (inner, basement crater diameter approximately 7.5 km, total diameter in sedimentary strata approximately 13.5 km). We present here results from geologic mapping, a 148.8 m deep core drilling from the center of the structure, detailed biostratigraphic dating of the structure's formation and its age correlation with Lockne, chemostratigraphy of the sedimentary infill, and indication for shock metamorphism in quartz from breccias below the crater infill. The drill core reveals, from bottom to the top, approximately 33 m of basement rocks with increased fracturing upward, approximately 10 m of polymict crystalline breccia with shock features, approximately 97 m of slumped Cambrian mudstone, approximately 4.7 m of a normally graded, polymict sedimentary breccia that in its uppermost part grades into sandstone and siltstone (cf. resurge deposits), and approximately 1.6 m of secular sediments. The combined data set shows that the Målingen structure formed in conjunction with the Lockne crater in the same marine setting. The shape and depth of the basement crater and the cored sequence of crystalline breccias with shocked quartz, slumped sediments, and resurge deposits support an impact origin. The stratigraphic and geographic relationship with Lockne suggests the Lockne and Målingen craters to be the first described doublet impact structure by a binary asteroid into a marine‐target setting.

Optical absorption, induced bleaching, and photoluminescence of CdSe nanoplatelets grown in cadmium octanoate matrix

CdSe nanoparticles (NPs) are chemically synthesized in thermotropic ionic liquid crystalline (LC) phase of cadmium octanoate that was used as a nanoreactor. The nanocomposite samples are obtained by the rapid cooling of the LC phase to room temperature. Observed doublet structure in absorption spectra of the nanocomposites is characteristic for the two-dimensional CdSe nanoplatelets (NPLs). The thicknesses of the CdSe NPLs are 1.6, 1.9 and 2.3 nm as determined from the absorption spectra, and correspond to 4, 5 and 6 CdSe monolayers, respectively. Induced simultaneous bleaching of the doublet components observed under femtosecond laser excitation, as well as photoluminescence spectra and their kinetics are found compatible with the model of excitons with heavy- and light-hole valence bands confined in nanoplatelets.