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Sample records for rb cs phase

  1. Electronic properties and phase transitions of RbC60 and CsC60: Investigation by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Tycko, R.; Dabbagh, G.; Murphy, D. W.; Zhu, Q.; Fischer, J. E.

    1993-09-01

    We report the results of 133Cs, 87Rb, and 13C NMR measurements on the alkali-metal fullerides CsC60 and RbC60. Measurements of NMR spectra and spin-lattice relaxation rates provide clear evidence for phase transitions near 300 K in both compounds, with substantial changes in their electronic properties at the phase transitions. The high-temperature phases are paramagnets, with an exchange coupling of roughly 2 cm-1 between electron spins that are localized primarily on C-60 ions. The 133Cs and 87Rb NMR frequency shifts and relaxation rates are determined by Fermi contact hyperfine couplings to the electron spins. The 13C relaxation rates are determined by dipolar hyperfine couplings. The electron-spin susceptibility is greatly reduced in the low-temperature phases

  2. Universal V-shaped phase diagram in the iron-based superconductors XFe2As2 (X = K, Rb, Cs)

    NASA Astrophysics Data System (ADS)

    Ouellet, Alexandre; Fallah Tafti, Fazel; Juneau-Fecteau, Alexandre; Faucher, Samuel; Lapointe-Major, Maxime; Doiron-Leyraud, Nicolas; Taillefer, Louis; Wang, Aifeng; Luo, Xigang; Chen, Xianhui

    2015-03-01

    Following the discovery of a sharp reversal in the dependence of Tc on pressure in KFe2As2 and CsFe2As2, we report a similar behavior in RbFe2As2. The application of hydrostatic pressure initially decreases Tc until a critical pressure Pc = 11 kbar where Tc suddenly starts to increase. For the three materials, we find a universal V-shaped temperature-pressure phase diagram, with identical slopes dTc/dP below and above Pc. Upon crossing Pc, the upper critical field Hc2 is observed to jump, by a similar factor for KFe2As2andRbFe2As2. We interpret these universal features in terms of a pressure-induced change in the pairing state of these superconductors.

  3. NMR relaxation study of the phase transitions and relaxation mechanisms of the alums MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals

    SciTech Connect

    Lim, Ae Ran; Paik, Younkee; Lim, Kye-Young

    2011-06-15

    The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the {sup 87}Rb and {sup 133}Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T{sub 1} are related to variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}. We also compared these {sup 87}Rb and {sup 133}Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO{sub 4}){sub 2}.12H{sub 2}O and MAl(SO{sub 4}){sub 2}.12H{sub 2}O crystals. - Graphical Abstract: The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb, Cs, and NH{sub 4}) single crystals have been investigated. Highlights: > The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) crystals {yields} The NMR spectra and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals {yields} The variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}.

  4. Comparative Raman spectroscopic study of phase stability and anharmonic effects in AZr2(PO4)3 (A = K, Rb and Cs)

    NASA Astrophysics Data System (ADS)

    Kamali, K.; Ravindran, T. R.; Ravi, C.

    2016-02-01

    AZr2(PO4)3 (A = Na, K, Rb, Cs) are a set of framework structured compounds that exhibit tunable ultralow thermal expansion over the wide temperature range of 293-1273 K. We report a systematic Raman spectroscopic investigation on AZr2(PO4)3 (A = K, Rb and Cs) compounds as a function of temperature in the range 80-860 K and pressures of up to 32 GPa. To get insight into the thermal expansion property, phonon anharmonicity has been investigated by studying the temperature and pressure dependence of Raman peak shifts and line widths and computed bulk modulus. We have compared the phase transition and amorphization pressures of the various members of AZr2(PO4)3 to account for the stability of the ambient rhombohedral phase. We find that unlike most of the anomalous thermal expansion materials, in AZr2(PO4)3 (A = K, Rb and Cs), the phonons that are anharmonic with temperature do not necessarily exhibit anharmonicity with pressure.

  5. High-resolution {sup 13}C nuclear magnetic resonance evidence of phase transition of Rb,Cs-intercalated single-walled nanotubes

    SciTech Connect

    Bouhrara, M.; Saih, Y.; Waagberg, T.; Goze-Bac, C.; Abou-Hamad, E.

    2011-09-01

    We present 13 C high-resolution magic-angle-turning (MAT) and magic angle spinning nuclear magnetic resonance data of Cs and Rb intercalated single walled carbon nanotubes. We find two distinct phases at different intercalation levels. A simple charge transfer is applicable at low intercalation level. The new phase at high intercalation level is accompanied by a hybridization of alkali (s) orbitals with the carbon (sp2) orbitals of the single walled nanotubes, which indicate bundle surface sites is the most probable alkali site.

  6. Simple-design ultra-low phase noise microwave frequency synthesizers for high-performing Cs and Rb vapor-cell atomic clocks

    NASA Astrophysics Data System (ADS)

    François, B.; Calosso, C. E.; Abdel Hafiz, M.; Micalizio, S.; Boudot, R.

    2015-09-01

    We report on the development and characterization of novel 4.596 GHz and 6.834 GHz microwave frequency synthesizers devoted to be used as local oscillators in high-performance Cs and Rb vapor-cell atomic clocks. The key element of the synthesizers is a custom module that integrates a high spectral purity 100 MHz oven controlled quartz crystal oscillator frequency-multiplied to 1.6 GHz with minor excess noise. Frequency multiplication, division, and mixing stages are then implemented to generate the exact output atomic resonance frequencies. Absolute phase noise performances of the output 4.596 GHz signal are measured to be -109 and -141 dB rad2/Hz at 100 Hz and 10 kHz Fourier frequencies, respectively. The phase noise of the 6.834 GHz signal is -105 and -138 dB rad2/Hz at 100 Hz and 10 kHz offset frequencies, respectively. The performances of the synthesis chains contribute to the atomic clock short term fractional frequency stability at a level of 3.1 × 10-14 for the Cs cell clock and 2 × 10-14 for the Rb clock at 1 s averaging time. This value is comparable with the clock shot noise limit. We describe the residual phase noise measurements of key components and stages to identify the main limitations of the synthesis chains. The residual frequency stability of synthesis chains is measured to be at the 10-15 level for 1 s integration time. Relevant advantages of the synthesis design, using only commercially available components, are to combine excellent phase noise performances, simple-architecture, low-cost, and to be easily customized for signal output generation at 4.596 GHz or 6.834 GHz for applications to Cs or Rb vapor-cell frequency standards.

  7. Simple-design ultra-low phase noise microwave frequency synthesizers for high-performing Cs and Rb vapor-cell atomic clocks.

    PubMed

    François, B; Calosso, C E; Abdel Hafiz, M; Micalizio, S; Boudot, R

    2015-09-01

    We report on the development and characterization of novel 4.596 GHz and 6.834 GHz microwave frequency synthesizers devoted to be used as local oscillators in high-performance Cs and Rb vapor-cell atomic clocks. The key element of the synthesizers is a custom module that integrates a high spectral purity 100 MHz oven controlled quartz crystal oscillator frequency-multiplied to 1.6 GHz with minor excess noise. Frequency multiplication, division, and mixing stages are then implemented to generate the exact output atomic resonance frequencies. Absolute phase noise performances of the output 4.596 GHz signal are measured to be -109 and -141 dB rad(2)/Hz at 100 Hz and 10 kHz Fourier frequencies, respectively. The phase noise of the 6.834 GHz signal is -105 and -138 dB rad(2)/Hz at 100 Hz and 10 kHz offset frequencies, respectively. The performances of the synthesis chains contribute to the atomic clock short term fractional frequency stability at a level of 3.1 × 10(-14) for the Cs cell clock and 2 × 10(-14) for the Rb clock at 1 s averaging time. This value is comparable with the clock shot noise limit. We describe the residual phase noise measurements of key components and stages to identify the main limitations of the synthesis chains. The residual frequency stability of synthesis chains is measured to be at the 10(-15) level for 1 s integration time. Relevant advantages of the synthesis design, using only commercially available components, are to combine excellent phase noise performances, simple-architecture, low-cost, and to be easily customized for signal output generation at 4.596 GHz or 6.834 GHz for applications to Cs or Rb vapor-cell frequency standards. PMID:26429467

  8. Simple-design ultra-low phase noise microwave frequency synthesizers for high-performing Cs and Rb vapor-cell atomic clocks

    SciTech Connect

    François, B.; Calosso, C. E.; Micalizio, S.; Abdel Hafiz, M.; Boudot, R.

    2015-09-15

    We report on the development and characterization of novel 4.596 GHz and 6.834 GHz microwave frequency synthesizers devoted to be used as local oscillators in high-performance Cs and Rb vapor-cell atomic clocks. The key element of the synthesizers is a custom module that integrates a high spectral purity 100 MHz oven controlled quartz crystal oscillator frequency-multiplied to 1.6 GHz with minor excess noise. Frequency multiplication, division, and mixing stages are then implemented to generate the exact output atomic resonance frequencies. Absolute phase noise performances of the output 4.596 GHz signal are measured to be −109 and −141 dB rad{sup 2}/Hz at 100 Hz and 10 kHz Fourier frequencies, respectively. The phase noise of the 6.834 GHz signal is −105 and −138 dB rad{sup 2}/Hz at 100 Hz and 10 kHz offset frequencies, respectively. The performances of the synthesis chains contribute to the atomic clock short term fractional frequency stability at a level of 3.1 × 10{sup −14} for the Cs cell clock and 2 × 10{sup −14} for the Rb clock at 1 s averaging time. This value is comparable with the clock shot noise limit. We describe the residual phase noise measurements of key components and stages to identify the main limitations of the synthesis chains. The residual frequency stability of synthesis chains is measured to be at the 10{sup −15} level for 1 s integration time. Relevant advantages of the synthesis design, using only commercially available components, are to combine excellent phase noise performances, simple-architecture, low-cost, and to be easily customized for signal output generation at 4.596 GHz or 6.834 GHz for applications to Cs or Rb vapor-cell frequency standards.

  9. Half metallic ferromagnetism in alkali metal nitrides MN (M = Rb, Cs): A first principles study

    SciTech Connect

    Murugan, A. Rajeswarapalanichamy, R. Santhosh, M. Sudhapriyanga, G.; Kanagaprabha, S.

    2014-04-24

    The structural, electronic and elastic properties of two alkali metal nitrides (MN: M= Rb, Cs) are investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At ambient pressure the two nitrides are stable in ferromagnetic state with CsCl structure. The calculated lattice parameters are in good agreement with the available results. The electronic structure reveals that these materials are half metallic in nature. A pressure-induced structural phase transition from CsCl to ZB phase is observed in RbN and CsN.

  10. Measurements of the ground-state polarizabilities of Cs, Rb, and K using atom interferometry

    NASA Astrophysics Data System (ADS)

    Gregoire, Maxwell D.; Hromada, Ivan; Holmgren, William F.; Trubko, Raisa; Cronin, Alexander D.

    2015-11-01

    We measured the ground-state static electric-dipole polarizabilities of Cs, Rb, and K atoms using a three-nanograting Mach-Zehnder atom beam interferometer. Our measurements provide benchmark tests for atomic structure calculations and thus test the underlying theory used to interpret atomic parity-nonconservation experiments. We measured αCs=4 π ɛ0×59.39 (9 ) Å3,αRb=4 π ɛ0×47.39 (8 ) Å3 , and αK=4 π ɛ0×42.93 (7 ) Å3 . In atomic units, these measurements are αCs=401.2 (7 ) ,αRb=320.1 (6 ) , and αK=290.0 (5 ) . We report ratios of polarizabilities αCs/αRb=1.2532 (10 ) ,αCs/αK=1.3834 (9 ) , and αRb/αK=1.1040 (9 ) with smaller fractional uncertainty because the systematic errors for individual measurements are largely correlated. Since Cs atom beams have short de Broglie wavelengths, we developed measurement methods that do not require resolved atom diffraction. Specifically, we used phase choppers to measure atomic beam velocity distributions, and we used electric field gradients to give the atom interference pattern a phase shift that depends on atomic polarizability.

  11. Prediction of phase equilibrium for the aqueous systems Rb+, Cs+/Cl-, SO{4/-}-H2O and K+, Cs+/Cl-, SO{4/2-}-H2O at 25°C

    NASA Astrophysics Data System (ADS)

    Hu, B.

    2013-05-01

    The Pitzer ion-interaction extended by Harvic and Weare was applied to predict the solubility isotherms of reciprocal quaternary systems in which mixed crystals are formed. On the basis of data concerning the binary and ternary subsystems, the four components systems Rb+, Cs+/Cl-, SO{4/2-}-H2O, and K+, Cs+/Cl-, SO{4/2-}-H2O were investigated at 25°C.The results of calculation can be used to model salt crystallization during the concentration of brines.

  12. Satellite bands of the RbCs molecule in the range of highly excited states

    NASA Astrophysics Data System (ADS)

    Rakić, Mario; Beuc, Robert; Bouloufa-Maafa, Nadia; Dulieu, Olivier; Vexiau, Romain; Pichler, Goran; Skenderović, Hrvoje

    2016-05-01

    We report on the observation of three RbCs satellite bands in the blue and green ranges of the visible spectrum. Absorption measurements are performed using all-sapphire cell filled with a mixture of Rb and Cs. We compare high resolution absorption spectrum of Rb-Cs vapor mixture with pure Rb and Cs vapor spectra from the literature. After detailed analysis, the new satellite bands of RbCs molecule at 418.3 nm, 468.3, and 527.5 nm are identified. The origin of these bands is discussed by direct comparison with difference potentials derived from quantum chemistry calculations of RbCs potential energy curves. These bands originate from the lower Rydberg states of the RbCs molecule. This study thus provides further insight into photoassociation of lower Rydberg molecular states, approximately between Cs(7s) + Rb(5s) and Cs(6s) + Rb(6p) asymptotes, in ultracold gases.

  13. Satellite bands of the RbCs molecule in the range of highly excited states.

    PubMed

    Rakić, Mario; Beuc, Robert; Bouloufa-Maafa, Nadia; Dulieu, Olivier; Vexiau, Romain; Pichler, Goran; Skenderović, Hrvoje

    2016-05-28

    We report on the observation of three RbCs satellite bands in the blue and green ranges of the visible spectrum. Absorption measurements are performed using all-sapphire cell filled with a mixture of Rb and Cs. We compare high resolution absorption spectrum of Rb-Cs vapor mixture with pure Rb and Cs vapor spectra from the literature. After detailed analysis, the new satellite bands of RbCs molecule at 418.3 nm, 468.3, and 527.5 nm are identified. The origin of these bands is discussed by direct comparison with difference potentials derived from quantum chemistry calculations of RbCs potential energy curves. These bands originate from the lower Rydberg states of the RbCs molecule. This study thus provides further insight into photoassociation of lower Rydberg molecular states, approximately between Cs(7s) + Rb(5s) and Cs(6s) + Rb(6p) asymptotes, in ultracold gases. PMID:27250309

  14. Dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs

    SciTech Connect

    McCarron, D. J.; Cho, H. W.; Jenkin, D. L.; Koeppinger, M. P.; Cornish, S. L.

    2011-07-15

    We report the formation of a dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of {sup 133}Cs via elastic collisions with {sup 87}Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to 2x10{sup 4} atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the {sup 87}Rb during the cooling, we create single-species {sup 133}Cs condensates of up to 6x10{sup 4} atoms.

  15. In-situ Dehydration Studies of Fully K- Rb- and Cs-exchanged Natrolites

    SciTech Connect

    Y Lee; D Seoung; D Liu; M Park; S Hong; H Chen; J Bai; C Kao; T Vogt; Y Lee

    2011-12-31

    In-situ synchrotron X-ray powder diffraction studies of K-, Rb-, and Cs-exchanged natrolites between room temperature and 425 C revealed that the dehydrated phases with collapsed frameworks start to form at 175, 150, and 100 C, respectively. The degree of the framework collapse indicated by the unit-cell volume contraction depends on the size of the non-framework cation: K-exchanged natrolite undergoes an 18.8% unit-cell volume contraction when dehydrated at 175 C, whereas Rb- and Cs-exchanged natrolites show unit-cell volume contractions of 18.5 and 15.2% at 150 and 100 C, respectively. In the hydrated phases, the dehydration-induced unit-cell volume reduction diminishes as the cation size increases and reveals increasingly a negative slope as smaller cations are substituted into the pores of the natrolite structure. The thermal expansion of the unit-cell volumes of the dehydrated K-, Rb-, and Cs-phases have positive thermal expansion coefficients of 8.80 x 10{sup -5} K{sup -1}, 1.03 x 10{sup -4} K{sup 01}, and 5.06 x 10{sup -5} K{sup -1}, respectively. Rietveld structure refinements of the dehydrated phases at 400 C reveal that the framework collapses are due to an increase of the chain rotation angles, {Psi}, which narrow the channels to a more elliptical shape. Compared to their respective hydrated structures at ambient conditions, the dehydrated K-exchanged natrolite at 400 C shows a 2.2-fold increase in {Psi}, whereas the dehydrated Rb- and Cs-natrolites at 400 C reveal increases of {Psi} by ca. 3.7 and 7.3 times, respectively. The elliptical channel openings of the dehydrated K-, Rb-, to Cs-phases become larger as the cation size increases. The disordered non-framework cations in the hydrated K-, Rb-, and Cs-natrolite order during dehydration and the subsequent framework collapse. The dehydrated phases of Rb- and Cs-natrolite can be stabilized at ambient conditions.

  16. Elastic scattering of electrons from Rb, Cs and Fr atoms

    NASA Astrophysics Data System (ADS)

    Gangwar, R. K.; Tripathi, A. N.; Sharma, L.; Srivastava, R.

    2010-04-01

    Differential, integrated elastic, momentum-transfer and total cross sections as well as differential S, T and U spin parameters for scattering of electrons from rubidium, caesium and francium atoms in the incident energy range up to 300 eV are calculated using a relativistic Dirac equation. The projectile electron-target atom interaction is represented by both real and complex parameter-free optical potentials for obtaining the solution of a Dirac equation for scattered electrons. The Dirac-Fock wavefunctions have been used to represent the Rb, Cs and Fr target atoms. The results of differential cross sections and spin asymmetry parameter S for e-Rb and e-Cs have been compared with the available experimental and theoretical results. Detailed results are reported for the elastic scattering of electrons from the ground states of a francium atom for the first time in the wide range of incident electron energies. The results of electron-Fr elastic scattering show the similar features to those obtained in the case of e-Rb and e-Cs elastic scattering.

  17. Insights into the structures of the gas-phase hydrated cations M⁺(H₂O)(n)Ar (M = Li, Na, K, Rb, and Cs; n = 3-5) using infrared photodissociation spectroscopy and thermodynamic analysis.

    PubMed

    Ke, Haochen; van der Linde, Christian; Lisy, James M

    2015-03-12

    The hydration of alkali cations yields a variety of structural conformers with varying numbers of water molecules in the first solvation shell. How these ions move from the aqueous phase into biological systems, such as at the entrance of an ion channel, depends on the interplay between competing intermolecular forces, which first must involve ion-water and water-water interactions. New infrared action spectra, using argon as a messenger or "spy", for Li(+), Na(+), and K(+), with up to five water molecules are reported, and new structural conformers determined from ab initio calculations, combined with previous results on Rb(+) and Cs(+), have identified structural transitions at each hydration level. These transitions are a result of the delicate balance between competing noncovalent interactions and represent a quantitative microscopic view of the macroscopic enthalpy-entropy competition between energy and structural variety. Smaller cations (Li(+) and Na(+)), with higher charge density, yield structural configurations with extended linear networks of hydrogen bonds. Larger cations (Rb(+) and Cs(+)), with lower charge density, generate configurations with cyclic hydrogen-bonded water subunits. It appears that K(+) is somewhat unique, with very simple (and predominantly) single structural conformers. This has led to the suggestion that K(+) can "move" easily in or through biological systems, concealing its identity as an ion, under the "appearance" or disguise of a water molecule. PMID:25651135

  18. Measurements of the Ground-State Polarizabilities of Cs, Rb, and K using Atom Interferometry

    NASA Astrophysics Data System (ADS)

    Gregoire, Maxwell; Hromada, Ivan; Holmgren, William; Trubko, Raisa; Cronin, Alex

    2016-05-01

    We measured the ground-state static electric-dipole polarizabilities of Cs, Rb, and K atoms with 0.2% uncertainty using a three-nanograting Mach-Zehnder atom beam interferometer. Since thermal Cs atoms have short de Broglie wavelengths, we developed measurement methods that do not require resolved atom diffraction: we used phase choppers to measure atomic beam velocity distributions, and electric field gradients to induce polarizability-dependent phase shifts. Our measurements provide benchmark tests for atomic structure calculations and thus test the underlying theory used to interpret atomic parity non-conservation experiments.

  19. Electron Impact Ionization Cross Sections in Rb and Cs.

    NASA Astrophysics Data System (ADS)

    Reddish, T. J.; Lukomski, M.; Sutton, S.; Kedzierski, W.; McConkey, J. W.; Bartschat, K.; Bartlett, P. L.; Stelbovics, A. T.; Bray, I.

    2006-05-01

    We present a new atom trapping technique for determining absolute, total ionisation cross sections (TICS) out of an excited atom. The novel feature of this method is in utilizing Doppler cooling of neutral atoms to determine ionisation cross sections. This fluorescence-monitoring experiment, which is a variant of the `trap loss' technique, has enabled us to obtain the experimental electron impact ionisation cross sections out of the Cs 6^2P3/2 excited state between 7 - 400 eV. New CCC, R-Matrix with Pseudo-States (RMPS), and Born approximation single ionisation cross sections (SICS) are also presented for both the ground and excited states of Cs and Rb, and compared with the available experimental data. The comparison of the results reveals the importance of the autoionisation and multiple ionisation contributions to the TICS. The autoionisation contribution appears to be substantial for ionisation out of the Cs 6^2P and Rb 5^2P excited states; ˜ 3-4 larger than the direct ionisation contribution predicted by CCC at ˜ 30-50 eV. This surprising result shows the importance of multi-electron processes in determining the ionisation cross sections of heavy alkali atoms.

  20. Universal V-shaped temperature-pressure phase diagram in the iron-based superconductors KFe2As2,RbFe2As2 , and CsFe2As2

    NASA Astrophysics Data System (ADS)

    Tafti, F. F.; Ouellet, A.; Juneau-Fecteau, A.; Faucher, S.; Lapointe-Major, M.; Doiron-Leyraud, N.; Wang, A. F.; Luo, X.-G.; Chen, X. H.; Taillefer, Louis

    2015-02-01

    We report a sudden reversal in the pressure dependence of Tc in the iron-based superconductor RbFe2As2 , at a critical pressure Pc =11 kbar. Combined with our prior results on KFe2As2 and CsFe2As2 , we find a universal V-shaped phase diagram for Tc versus P in these fully hole-doped 122 materials, when measured relative to the critical point (Pc,Tc). From measurements of the upper critical field Hc 2(T ) under pressure in KFe2As2 and RbFe2As2 , we observe the same twofold jump in (1 /Tc) (-∂Hc2/∂T )Tc across Pc, compelling evidence for a sudden change in the structure of the superconducting gap. We argue that this change is due to a transition from one pairing state to another, with different symmetries on either side of Pc. We discuss a possible link between scattering and pairing, and a scenario where a d -wave state favored by high-Q scattering at low pressure changes to a state with s± symmetry favored by low-Q scattering at high pressure.

  1. Investigation of substitution effects and the phase transition in type-I clathrates Rb{sub x}Cs{sub 8-x}Sn{sub 44}square{sub 2} (1.3<=x<=2.1) using single-crystal X-ray diffraction, Raman spectroscopy, heat capacity and electrical resistivity measurements

    SciTech Connect

    Kaltzoglou, Andreas; Faessler, Thomas F.; Gold, Christian; Scheidt, Ernst-Wilhelm; Scherer, Wolfgang; Kume, Tetsuji; Shimizu, Hiroyasu

    2009-10-15

    The substitution of cations in Rb{sub x}Cs{sub 8-x}Sn{sub 44}square{sub 2}(1.3<=x<=2.1) is reported. The compounds crystallize at room temperature in the space group la3-bard adopting the type-I clathrate 2x2x2 superstructure with partly ordered framework vacancies (square), whereas at higher temperatures they transform to the primitive, more disordered modification (space group Pm3-barn). The guest atom distributions in the Sn cages on the Rb: Cs ratios is studied by means of single-crystal X-ray diffraction for Rb{sub 2.1(1)}Cs{sub 5.8(1)}Sn{sub 44} at T=293 K (1), Rb{sub 1.42(8)}Cs{sub 6.58(8)}Sn{sub 44} at T=293 K (2a), Rb{sub 1.46(5)}Cs{sub 6.54(5)}Sn{sub 44} at T=373 K (2b) and Rb{sub 1.32(8)}Cs{sub 6.68(8)}Sn{sub 44} at T=293 K (3). The structural order-disorder phase transition influences the electrical resistivity. The hysteresis observed for the electrical resistivity in combination with the symmetric shape of the specific heat anomaly suggests that the transformation is of first-order type and is characterized by an entropy change of about 2.5 J mol{sup -1} K{sup -1}. The Raman spectrum for the low-temperature modification of 2 is also reported. - Graphical Abstract: The effects of substitution of cations in the type-I clathrates Rb{sub x}Cs{sub 8-x}Sn{sub 44} (1.3<=x<=2.1) are reported. The distribution of the guests in the Sn cages under different reaction stoichiometries and annealing times is studied by X-ray diffraction. A structural phase transition in Rb{sub 1.4}Cs{sub 6.6}Sn{sub 44} at 333-363 K affects significantly the electrical resistivity and heat capacity.

  2. New-Structure-Type Fe-Based Superconductors: CaAFe4As4 (A = K, Rb, Cs) and SrAFe4As4 (A = Rb, Cs).

    PubMed

    Iyo, Akira; Kawashima, Kenji; Kinjo, Tatsuya; Nishio, Taichiro; Ishida, Shigeyuki; Fujihisa, Hiroshi; Gotoh, Yoshito; Kihou, Kunihiro; Eisaki, Hiroshi; Yoshida, Yoshiyuki

    2016-03-16

    Fe-based superconductors have attracted research interest because of their rich structural variety, which is due to their layered crystal structures. Here we report the new-structure-type Fe-based superconductors CaAFe4As4 (A = K, Rb, Cs) and SrAFe4As4 (A = Rb, Cs), which can be regarded as hybrid phases between AeFe2As2 (Ae = Ca, Sr) and AFe2As2. Unlike solid solutions such as (Ba1-xKx)Fe2As2 and (Sr1-xNax)Fe2As2, Ae and A do not occupy crystallographically equivalent sites because of the large differences between their ionic radii. Rather, the Ae and A layers are inserted alternately between the Fe2As2 layers in the c-axis direction in AeAFe4As4 (AeA1144). The ordering of the Ae and A layers causes a change in the space group from I4/mmm to P4/mmm, which is clearly apparent in powder X-ray diffraction patterns. AeA1144 is the first known structure of this type among not only Fe-based superconductors but also other materials. AeA1144 is formed as a line compound, and therefore, each AeA1144 has its own superconducting transition temperature of approximately 31-36 K. PMID:26943024

  3. Elastic Scattering of Ultracold 133Cs and 85Rb Atoms in Triplet State

    NASA Astrophysics Data System (ADS)

    Sun, Jin-Feng; Hu, Qiu-Bo; Zhu, Zun-Lue; Wang, Xiao-Fei; Zhang, Ji-Cai

    2007-06-01

    Elastic scattering properties of the ultracold interaction for the triplet state of 133Cs and 85Rb atoms are studied using two kinds of potentials by the same phase Φ. One is the interpolation potential, and another is Lennard-Jones potential (LJ12,6). The radial Schrödinger equation is also solved using two computational methods, the semiclassical method (WKB), and the Numerov method. Our results are found to be in an excellent agreement with the more recent theoretical values. It shows that the two potentials and methods are applicable for studying ultracold collisions between the mixing alkali atoms.

  4. Influence of Rb, Cs, and Ba on the superconductivity of magnesium diboride

    NASA Astrophysics Data System (ADS)

    Palnichenko, A. V.; Vyaselev, O. M.; Sidorov, N. S.

    2007-10-01

    Magnesium diboride has been thermally treated in the presence of Rb, Cs, and Ba. The magnetic susceptibility shows the possible onsets of superconductivity in the resulting samples at 52 K (Rb), 58 K (Cs), and 45 K (Ba). Room-temperature 11B NMR indicates the cubic symmetry of the electric field gradient at the boron site for the samples reacted with Rb and Cs, in contrast to the axial symmetry in the initial MgB2 and in the sample treated with Ba.

  5. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl{sub 6}

    SciTech Connect

    Pilania, G. Uberuaga, B. P.

    2015-03-21

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl{sub 6} using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl{sub 3} and RbZnCl{sub 3}) forming the double perovskite exhibit a stark contrast. While CsCaCl{sub 3} is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl{sub 3} is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositions in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl{sub 6} can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. The computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities.

  6. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl6

    DOE PAGESBeta

    Pilania, G.; Uberuaga, B. P.

    2015-03-19

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl6 using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl3 and RbZnCl3) forming the double perovskite exhibit a stark contrast. While CsCaCl3 is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl3 is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositionsmore » in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl6 can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. As a result, the computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities.« less

  7. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl6

    SciTech Connect

    Pilania, G.; Uberuaga, B. P.

    2015-03-19

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl6 using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl3 and RbZnCl3) forming the double perovskite exhibit a stark contrast. While CsCaCl3 is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl3 is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositions in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl6 can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. As a result, the computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities.

  8. Narrow 87Rb and 133Cs hyperfine transitions in evacuated wall-coated cells

    NASA Technical Reports Server (NTRS)

    Robinson, H. G.; Johnson, C. E.

    1983-01-01

    An extension of work on wall-coated cells was made to include observation by a triple resonance technique of the 0-0 hyperfine transitions in 87Rb and 133Cs. Conventional RF excited lamps were used. Interest in such cells is for possible application in atomic clocks. The Rb cell would appear to remain especially promising in this respect.

  9. Mixed Valent Gold Oxides: Syntheses, Structures, and Properties of Rb 5Au 3O 2, Rb 7Au 5O 2, and Cs 7Au 5O 2

    NASA Astrophysics Data System (ADS)

    Mudring, Anja-Verena; Nuss, Jürgen; Wedig, Ulrich; Jansen, Martin

    2000-11-01

    The title compounds Rb5Au3O2, Rb7Au5O2, and Cs7Au5O2 are the first examples of mixed valent phases containing gold in the oxidation states +1 and -1. Their crystal structures (Rb5Au3O2, Pbam, a=736.4(1) pm, b=1430.8(2) pm, c=567.9(1) pm, Z=2, R(F)=0.053, 647 reflections; Rb7Au5O2, Immm, a=567.1(2) pm, b=930.1(1) pm, C=1659.4(3) pm, Z=2, R(F)=0.066, 409 reflections; Cs7Au5O2, Immm, a=599.4(1) pm, b=960.6(3) pm, c=1720.8(12) pm, Z=2, R(F)=0.039, 386 reflections) are characterized by the combination of distinctive structural features of gold(I) oxides and aurides: for Au(+1) a typical linear coordination by oxygen is found and the surroundings of Au(-1) bear a close resemblance to the binary 1:1 aurides. In consequence the overall structures of Rb5Au3O2 and M7Au5O2 can be described as intergrowths of M3AuO2 and MAu (M=Rb, Cs), constituting members of a homologous series [MAu]n[M3AuO2] with n=2 and 4, respectively. The crystal chemical evidence for the valence states assumed, also confirmed by Mößbauer spectroscopy, is supported by various band structure calculations (Hartee-Fock and density functional) clearly indicating the coexistence of two different oxidation states. The compounds have been synthesized by reacting binary aurides MAu and alkali monoxides M2O (M=Rb, Cs) with elemental gold in the required stochiometric amounts. Hereby, a further astonishing parallel to the chemistry of halogens is revealed. Like these, gold disproportionates upon interaction with bases.

  10. Improved tests of local position invariance using 87Rb and 133Cs fountains.

    PubMed

    Guéna, J; Abgrall, M; Rovera, D; Rosenbusch, P; Tobar, M E; Laurent, Ph; Clairon, A; Bize, S

    2012-08-24

    We report tests of local position invariance based on measurements of the ratio of the ground state hyperfine frequencies of 133Cs and 87Rb in laser-cooled atomic fountain clocks. Measurements extending over 14 years set a stringent limit to a possible variation with time of this ratio: d ln(ν(Rb)/ν(Cs))/dt=(-1.39±0.91)×10(-16) yr(-1). This improves by a factor of 7.7 over our previous report [H. Marion et al., Phys. Rev. Lett. 90, 150801 (2003)]. Our measurements also set the first limit to a fractional variation of the Rb/Cs frequency ratio with gravitational potential at the level of c(2)d ln(ν(Rb)/ν(Cs))/dU=(0.11±1.04)×10(-6), providing a new stringent differential redshift test. The above limits equivalently apply to the fractional variation of the quantity α(-0.49)(g(Rb)/g(Cs)), which involves the fine-structure constant α and the ratio of the nuclear g-factors of the two alkalis. The link with variations of the light quark mass is also presented together with a global analysis combining other available highly accurate clock comparisons. PMID:23002732

  11. Hyperfine frequencies of 87Rb and 133Cs atoms in Xe gas

    NASA Astrophysics Data System (ADS)

    McGuyer, B. H.; Xia, T.; Jau, Y.-Y.; Happer, W.

    2011-09-01

    The microwave resonant frequencies of ground-state 87Rb and 133Cs atoms in Xe buffer gas are shown to have a relatively large nonlinear dependence on the Xe pressure, presumably because of RbXe or CsXe van der Waals molecules. The nonlinear shifts for Xe are opposite in sign to the previously measured shifts for Ar and Kr, even though all three gases have negative linear shifts. The Xe data show striking discrepancies with the previous theory for nonlinear shifts. Most of this discrepancy is eliminated by accounting for the spin-rotation interaction, γN·S, in addition to the hyperfine-shift interaction, δAI·S, in the molecules. To the limit of our experimental accuracy, the shifts of 87Rb and 133Cs in He, Ne, and N2 were linear with pressure.

  12. Superconductivity in Fe-Based Compound EuAFe4As4 (A = Rb and Cs)

    NASA Astrophysics Data System (ADS)

    Kawashima, Kenji; Kinjo, Tatsuya; Nishio, Taichiro; Ishida, Shigeyuki; Fujihisa, Hiroshi; Gotoh, Yoshito; Kihou, Kunihiro; Eisaki, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira

    2016-06-01

    We report the discovery of a novel Fe-based superconductor EuAFe4As4 (A = Rb, Cs) and describe its superconducting properties. EuAFe4As4 has a tetragonal unit cell with a P4/mmm (No. 123) space group, indicating that this material is an 1144-type compound. The magnetic susceptibility and electrical resistivity indicate superconducting transitions at approximately 36 and 35 K for EuRbFe4As4 and EuCsFe4As4, respectively. Moreover, an anomalous magnetic transition appears at approximately 15 K, suggesting the coexistence of superconductivity and a magnetic ordered state formed by the Eu2+ ions. The determined upper critical magnetic fields and coherence lengths are approximately 920 kOe and 1.8 nm for EuRbFe4As4 and 875 kOe and 1.9 nm for EuCsFe4As4, respectively.

  13. Dual species entanglement of Rb and Cs qubits with Rydberg blockade for crosstalk free qubit measurements

    NASA Astrophysics Data System (ADS)

    Baker, Kevin; Yu, Zhaoning; Ebert, Matthew; Sun, Yuan; Saffman, Mark

    2016-05-01

    One of the outstanding challenges facing neutral atom qubit approaches to quantum computation is suppression of crosstalk between proximal qubits due to scattered light that is generated during optical pumping and measurement operations. We have recently proposed a dual species approach to solving this challenge whereby computational qubits encoded in Cs atoms are entangled with Rb atoms via an interspecies Rydberg interaction. The quantum state of a Cs atom can then be readout by measuring the state of a Rb atom. The difference in resonant wavelengths of the two species effectively suppresses crosstalk. We will present progress towards experimental demonstration of dual species entanglement using Rb and Cs atoms cotrapped in a single beam optical trap. Work supported by the ARL CDQI.

  14. CsPbCl 3 nanocrystals dispersed in the Rb 0,8Cs 0,2Cl matrix studied by far-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Voloshynovskii, A.; Savchyn, P.; Karbovnyk, I.; Myagkota, S.; Cestelli Guidi, M.; Piccinini, M.; Popov, A. I.

    2009-04-01

    The comparative far-infrared spectroscopy studies of Rb 0.8Cs 0.2Cl and Rb 0.8Cs 0.2Cl containing CsPbCl 3 nanocrystals between 170 and 320 K are reported. The effect of cesium lead chloride nanocrystals on the phonon modes of the host matrix, particularly manifested in different temperature behavior of LO-TO splitting and the temperature dependence of high frequency dielectric constant, are demonstrated.

  15. Syntheses, crystal structure, and electronic properties of the five ABaMQ4 compounds RbBaPS4, CsBaPS4, CsBaVS4, RbBaVSe4, and CsBaVSe4

    NASA Astrophysics Data System (ADS)

    Mesbah, Adel; Prakash, Jai; Rocca, Dario; Lebègue, Sébastien; Beard, Jessica C.; Lewis, Benjamin A.; Ibers, James A.

    2016-01-01

    Five new compounds belonging to the ABaMQ4 family were synthesized by solid-state chemistry at 1123 K. The compounds RbBaPS4, CsBaPS4, CsBaVS4, RbBaVSe4, and CsBaVSe4 are isostructural and have the TlEuPS4 structure type. They crystallize in space group D162h - Pnma of the orthorhombic system. Their structure consists isolated MQ4 tetrahedra separated by A and Ba atoms to form a salt-like structure. Density Functional Theory (DFT) calculations of the electronic structures with the use of the HSE functional suggest that the compounds are semiconductors with calculated band gaps of 3.3 eV (RbBaPS4), 3.4 eV (CsBaPS4), 2.3 eV (CsBaVS4), and 1.6 eV (RbBaVSe4).

  16. Magnetic decoupling of 129Xe-Rb and 129Xe-Cs binary spin exchange

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu; Kuzma, Nicholas N.; Happer, William

    2003-02-01

    We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of 129Xe atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For 129Xe-Rb, where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for 129Xe-Rb is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.

  17. First-principle study of half-metallic ferromagnetism in rocksalt XO (X=Li, K, Rb, Cs)

    NASA Astrophysics Data System (ADS)

    Lei, Gang; Liu, Xiao-Xiong; Xie, Huan-Huan; Li, Lei; Gao, Qiang; Deng, Jian-Bo

    2016-01-01

    By using first-principles calculation, we have studied the structure, electronic and magnetic properties of XO (X=Li, K, Rb, Cs) at equilibrium lattice constant in the rocksalt structure. The calculations reveal that the ferromagnetic phase of these compounds is more stable than the nonferromagnetic phase ones and they can be synthetized. All the compounds show half-metallic behaviors at equilibrium lattice constant with an integer magnetic moment of 1μB per formula unit. The half-metallic band gap of these compounds is very large and all the compounds keep their half-metallic characteristic in a wide range of lattice constants. Therefore, we expect that they can be useful in spintronic applications.

  18. Ground electronic states of RbO2+, CsO2+ and FrO2: the ionization energies of RbO2 and CsO2.

    PubMed

    Lee, Edmond P F; Wright, Timothy G

    2005-04-14

    Calculations are performed to establish the ground electronic states of RbO2+, CsO2+, and FrO2. In the case of the cations, both linear and C2v orientations were considered; for FrO2, the two lowest electronic states, 2A2 and 2B2, were considered in C2v symmetry. In addition, calculations were also performed on the x2 A2 ground states of RbO2 and CsO2 to derive ionization energies. Binding energies and heats of formation are also derived. The bonding in FrO2 is found to be less ionic than that of RbO2 and CsO2. PMID:16833657

  19. Rb and Cs deposition on epitaxial graphene grown on 6H -SiC(0001)

    NASA Astrophysics Data System (ADS)

    Watcharinyanon, S.; Virojanadara, C.; Johansson, L. I.

    2011-11-01

    Epitaxial graphene grown on the silicon-terminated SiC(0001) is doped by alkali metals deposited on the surface. The synchrotron radiation based photoelectron spectroscopy results presented reveal that Rb and Cs deposited on monolayer graphene samples, grown on the silicon-terminated SiC(0001), gives rise to n-type doping, i.e. electron transfer from the metal to the graphene layer. The Dirac point of the single π-cone is found to shift downwards away from the Fermi level by ca. 1.0 eV after alkali metal depositions. The adsorbed Rb and Cs atoms do initially disrupt the bonds in the graphene layer but after heating the bonds appear to be recreated when the alkali metal coverage start to decrease due to thermal desorption. None of these two alkali metals do intercalate into the graphene and buffer layer after depositing at room temperature or after heating. This is contrary to the case of Li where intercalation occurred directly after deposition.

  20. Structures and synthesis of framework Rb and Cs uranyl arsenates and their relationships with their phosphate analogues

    NASA Astrophysics Data System (ADS)

    Locock, Andrew J.; Burns, Peter C.

    2003-11-01

    Two hydrated uranyl arsenates, Cs 2(UO 2)[(UO 2)(AsO 4)] 4(H 2O) 2 ( CsUAs) and Rb 2(UO 2)[(UO 2)(AsO 4)] 4(H 2O) 4.5 ( RbUAs), were synthesized by hydrothermal methods. Intensity data were collected at room temperature using Mo Kα radiation and a CCD-based area detector. The crystal structure of RbUAs was solved by direct methods, whereas the structure model of the phosphate Cs 2(UO 2)[(UO 2)(PO 4)] 4(H 2O) 2 was used for CsUAs; both were refined by full-matrix least-squares techniques on the basis of F2 to agreement indices ( CsUAs, RbUAs) w R2=0.061,0.041, for all data, and R1=0.032,0.021, calculated for 5098, 4991 unique observed reflections (| Fo|>4 σF), respectively. The compound CsUAs is orthorhombic, space group Cmc2 1, Z=4, a=15.157(2), b=14.079(2), c=13.439(2) Å, V=2867.9(1) Å 3. RbUAs is monoclinic, space group C2/ m, Z=4, a=13.4619(4), b=15.8463(5), c=14.0068(4) Å, β=92.311(1)°, V=2985.52(2) Å 3. The structures consist of sheets of arsenate tetrahedra and uranyl pentagonal bipyramids, with composition [(UO 2)(AsO 4)] -, that are topologically identical to the uranyl silicate sheets in uranophane-beta. These sheets are connected by a uranyl pentagonal bipyramid in the interlayer that shares corners with two arsenate tetrahedra on each of two adjacent sheets and whose fifth equatorial vertex is an H 2O group, resulting in an open framework with alkali metal cations in the larger cavities of the structures. CsUAs is isostructural with its phosphate analogue, and has two Cs atoms and a H 2O group in its structural cavities. RbUAs is not isostructural with its phosphate analogue, although it has a homeotypic framework. Its structural cavities are occupied by three Rb atoms and four H 2O groups; one Rb position and three of the interstitial H 2O groups are half-occupied. The partial occupancies of these positions probably result from the accommodation of the larger As atoms (relative to P) in the framework and resultant larger cavities.

  1. Magnetic-sublevel-independent magic wavelengths: Application to Rb and Cs atoms

    NASA Astrophysics Data System (ADS)

    Singh, Sukhjit; Sahoo, B. K.; Arora, Bindiya

    2016-06-01

    A generic scheme to trap atoms at the magic wavelengths λmagic that are independent of vector and tensor components of the interactions of the atoms with the external electric field is presented. The λmagic for the laser cooling D2 lines in the Rb and Cs atoms are demonstrated and their corresponding polarizability values without vector and tensor contributions are given. Consequently, these λmagic are independent of magnetic sublevels and hyperfine levels of the atomic states involved in the transition, thus, they can offer unique approaches to carrying out many high-precision measurements with minimal systematics. Inevitably, the proposed technique can also be used for electronic or hyperfine transitions in other atomic systems.

  2. Room temperature light emission from the low-dimensional semiconductors AZrPS{sub 6} ( A = K, Rb, Cs).

    SciTech Connect

    Banerjee, S.; Szarko, J. M.; Yuhas, B. D.; Malliakas, C. D.; Chen, L. X.; Kanatzidis, M. G.

    2010-03-29

    The new semiconducting thiophosphate compounds KZrPS{sub 6}, RbZrPS{sub 6}, and CsZrPS{sub 6} exhibit red light emission at room temperature. The materials have longer photoluminescence lifetimes than most of the inorganic chalcogenide semiconductors. They can be solution processed into thin films for potential device fabrication.

  3. Syntheses and structures of six compounds in the A{sub 2}LiMS{sub 4} (A=K, Rb, Cs; M=V, Nb, Ta) family

    SciTech Connect

    Huang Fuqiang; Deng Bin; Ibers, James A. . E-mail: ibers@chem.northwestern.edu

    2005-01-15

    Six new compounds in the A{sub 2}LiMS{sub 4} (A=K, Rb, Cs; M=V, Nb, Ta) family, namely K{sub 2}LiVS{sub 4}, Rb{sub 2}LiVS{sub 4}, Cs{sub 2}LiVS{sub 4}, Rb{sub 2}LiNbS{sub 4}, Cs{sub 2}LiNbS{sub 4}, and Rb{sub 2}LiTaS{sub 4}, have been synthesized by the reactions of the elements in Li{sub 2}S/S/A{sub 2}S{sub 3} (A=K, Rb, Cs) fluxes at 773K. The A and M atoms play a role in the coordination environment of the Li atoms, leading to different crystal structures. Coordination numbers of Li atoms are five in K{sub 2}LiVS{sub 4}, four in A{sub 2}LiVS{sub 4} (A=Rb, Cs) and Cs{sub 2}LiNbS{sub 4}, and both four and five in Rb{sub 2}LiMS{sub 4} (M=Nb, Ta). The A{sub 2}LiVS{sub 4} (A=Rb, Cs) structure comprises one-dimensional chains of {sub {infinity}}{sup 1}[LiVS{sub 4}] tetrahedra. The Rb{sub 2}LiMS{sub 4} (M=Nb, Ta) structure is composed of two-dimensional {sub {infinity}}{sup 2}[LiMS{sub 4}] layers. The Cs{sub 2}LiNbS{sub 4} structure contains one-dimensional {sub {infinity}}{sup 1}[LiNbS{sub 4}] chains that are related to the Rb{sub 2}LiMS{sub 4} layers. The K{sub 2}LiVS{sub 4} structure contains a different kind of {sub {infinity}}{sup 1}[LiVS{sub 4}] layer.

  4. First-principles study on the bulk and (1 1 1) surface half-metallicity of KS and RbS in CsCl structure

    SciTech Connect

    Li, Lei; Lei, Gang; Gao, Qiang; Deng, Jian-Bo; Hu, Xian-Ru

    2015-08-15

    Graphical abstract: Spin-polarized total and atomic DOS at S-(1 1 1) terminated slab and bulk in CsCl-type RbS. - Highlights: • The half metallic properties of CsCl-type RbS and KS have been studied. • The RbS's and KS's (1 1 1) slabs have been investigated. • Surface energy of RbS's and KS's (1 1 1) slabs are calculated. - Abstract: The electronic and magnetic properties of RbS and KS in CsCl structure have been investigated by using the full-potential local-orbital minimum-basis method. Calculating the relation between the total energies and lattice parameters for RbS and KS, we find out that the equilibrium lattice parameters are 4.02 Å and 3.84 Å for RbS and KS, respectively. According to our calculations in generalized gradient approximation approximation, both RbS and KS are half-metallic ferromagnets with the magnetic moments of 1 μ{sub B} per formula unit, and band gap of 4.287 eV for RbS and 4.395 eV for KS. We also have studied the electronic and magnetic properties of (1 1 1) surfaces of RbS and KS, and have found out that the half-metallicity of their bulk is preserved in all of those surfaces. Finally, through the calculations of formation energy of RbS and KS, it is found that their thin films are stable in the equilibrium conditions, and the Rb-terminated (1 1 1) slab of RbS and the K-terminated (1 1 1) slab of KS are more stable than their S-terminated (1 1 1) slabs. All of the above properties lead the compounds of RbS and KS in CsCl structure to be promising candidates for spintronic applications.

  5. Intercalation of heavy alkali metals (K, Rb and Cs) in the bundles of single wall nanotubes

    NASA Astrophysics Data System (ADS)

    Duclaux, L.; Méténier, K.; Lauginie, P.; Salvetat, J. P.; Bonnamy, S.; Beguin, F.

    2000-11-01

    The electric-arc discharge carbon deposits (collaret) containing Single Wall Carbon Nanotubes (SWNTs) were heat treated at 1600 °C during 2 days under N2 flow in order to eliminate the Ni catalyst by sublimation, without modifications of the SWNTs ropes. Sorting this deposit by gravity enabled to obtain in the coarsest particles higher amount of SWNTs ropes than in other particle sizes. The coarser particles of the carbon deposits were reacted with the alkali metals vapor giving intercalated samples with a MC8 composition. The intercalation led to an expansion of the 2D lattice of the SWNTs so that the alkali metals were intercalated in between the tubes within the bundles. Disordered lattices were observed after intercalation of Rb and Cs. The simulations of the X-ray diffractograms of SWNTs reacted with K, gave the best fit for three K ions occupying the inter-tubes triangular cavities. The investigations by EPR, and 13C NMR, showed that doped carbon deposits are metallic.

  6. Investigation on ultracold RbCs molecules in (2)0{sup +} long-range state below the Rb(5S{sub 1/2}) + Cs(6P{sub 1/2}) asymptote by high resolution photoassociation spectroscopy

    SciTech Connect

    Yuan, Jinpeng; Ji, Zhonghua; Li, Zhonghao; Zhao, Yanting Xiao, Liantuan; Jia, Suotang

    2015-07-28

    We present high resolution photoassociation spectroscopy of RbCs molecules in (2)0{sup +} long-range state below the Rb(5S{sub 1/2}) + Cs(6P{sub 1/2}) asymptote and derive the corresponding C{sub 6} coefficient, which is used to revise the potential energy curves. The excited state molecules are produced in a dual-species dark spontaneous force optical trap and detected by ionizing ground state molecules after spontaneous decay, using a high sensitive time-of-flight mass spectrum. With the help of resonance-enhanced two-photon ionization technique, we obtain considerable high resolution photoassociation spectrum with rovibrational states, some of which have never been observed before. By applying the LeRoy-Bernstein method, we assign the vibrational quantum numbers and deduce C{sub 6} coefficient, which agrees with the theoretical value of A{sup 1}Σ{sup +} state correlated to Rb(5S{sub 1/2}) + Cs(6P{sub 1/2}) asymptote. The obtained C{sub 6} coefficient is used to revise the long-range potential energy curve for (2)0{sup +} state, which possesses unique A − b mixing characteristic and can be a good candidate for the production of absolutely ground state molecule.

  7. Investigation on ultracold RbCs molecules in (2)0(+) long-range state below the Rb(5S1/2) + Cs(6P1/2) asymptote by high resolution photoassociation spectroscopy.

    PubMed

    Yuan, Jinpeng; Ji, Zhonghua; Li, Zhonghao; Zhao, Yanting; Xiao, Liantuan; Jia, Suotang

    2015-07-28

    We present high resolution photoassociation spectroscopy of RbCs molecules in (2)0(+) long-range state below the Rb(5S1/2) + Cs(6P1/2) asymptote and derive the corresponding C6 coefficient, which is used to revise the potential energy curves. The excited state molecules are produced in a dual-species dark spontaneous force optical trap and detected by ionizing ground state molecules after spontaneous decay, using a high sensitive time-of-flight mass spectrum. With the help of resonance-enhanced two-photon ionization technique, we obtain considerable high resolution photoassociation spectrum with rovibrational states, some of which have never been observed before. By applying the LeRoy-Bernstein method, we assign the vibrational quantum numbers and deduce C6 coefficient, which agrees with the theoretical value of A(1)Σ(+) state correlated to Rb(5S1/2) + Cs(6P1/2) asymptote. The obtained C6 coefficient is used to revise the long-range potential energy curve for (2)0(+) state, which possesses unique A - b mixing characteristic and can be a good candidate for the production of absolutely ground state molecule. PMID:26233133

  8. Investigation on ultracold RbCs molecules in (2)0+ long-range state below the Rb(5S1/2) + Cs(6P1/2) asymptote by high resolution photoassociation spectroscopy

    NASA Astrophysics Data System (ADS)

    Yuan, Jinpeng; Ji, Zhonghua; Li, Zhonghao; Zhao, Yanting; Xiao, Liantuan; Jia, Suotang

    2015-07-01

    We present high resolution photoassociation spectroscopy of RbCs molecules in (2)0+ long-range state below the Rb(5S1/2) + Cs(6P1/2) asymptote and derive the corresponding C6 coefficient, which is used to revise the potential energy curves. The excited state molecules are produced in a dual-species dark spontaneous force optical trap and detected by ionizing ground state molecules after spontaneous decay, using a high sensitive time-of-flight mass spectrum. With the help of resonance-enhanced two-photon ionization technique, we obtain considerable high resolution photoassociation spectrum with rovibrational states, some of which have never been observed before. By applying the LeRoy-Bernstein method, we assign the vibrational quantum numbers and deduce C6 coefficient, which agrees with the theoretical value of A1Σ+ state correlated to Rb(5S1/2) + Cs(6P1/2) asymptote. The obtained C6 coefficient is used to revise the long-range potential energy curve for (2)0+ state, which possesses unique A - b mixing characteristic and can be a good candidate for the production of absolutely ground state molecule.

  9. Theoretical transition probabilities between the lowest 2S, 2P and 2D states of Na, K, Rb and Cs

    NASA Technical Reports Server (NTRS)

    Langhoff, S. R.; Bauschlicher, C. W., Jr.; Partridge, H.

    1985-01-01

    Theoretical transition probabilities between the lowest 2S, 2P and 2D states of the alkali atoms Na through Cs have been computed using near Hartree-Fock quality Slater basis sets. The important core-valence correlation effects are incorporated explicitly by a configuration-interaction procedure. For Cs, the calculations were repeated using a Gaussian basis set so that relativistic effects could be incorporated through an effective core potential procedure. The best calculated electric quadrupole Einstein coefficients are Na(196.3/s), K(103.6/s), Rb(72.4/s) and Cs(19.7/s). Core-valence effects become increasingly important down the column, and reduce the quadrupole transition strengths to about the same degree as for the 2P-2S and 2D-2P dipole-allowed transitions. Relativistic effects increase the quadrupole moment of Cs, but less so than in Ba, presumably because the alkali 2D states are more diffuse.

  10. Rydberg States of rb and cs Atoms on Helium Nanodroplets: a Rydberg-Ritz Analysis

    NASA Astrophysics Data System (ADS)

    Lackner, Florian; Krois, Gunter; Ernst, Wolfgang E.

    2013-06-01

    Rydberg series of Rb and Cs atoms on the surface of helium nanodroplets (He_{N}) have been studied by resonance enhanced multi-photon ionization spectroscopy and laser induced fluorescence spectroscopy. The recorded excitation spectra are analyzed by using a Rydberg-Ritz approach. The dependence of the quantum defects on the principal quantum number within a Rydberg series gives insight into the interaction between the alkali atom's valence electron and the superfluid helium droplet. For higher excited states a screening of the valence electron from the alkali atom core by the helium droplet is observed. For lower states the strength of the screening effect decreases and the quantum defects are found to lie closer to free atom values. In addition, the large spin-orbit (SO) constant of the Cs-He_{N} nP(^{2}Π) states allows a detailed study of the influence of the helium droplet on the SO splitting as function of the principal quantum number. Within the pseudo-diatomic picture the alkali-He_{N} system represents a diatomic molecule. The coupling of the Cs valence electrons spin and the orbital angular momentum with the intermolecular axis, which is defined by the connection between the droplet center and the alkali nucleus, depends on the strength of the atomic SO interaction. While the splitting of the 6^{2}P_{1/2}(^{2}Π_{1/2}) and 6^{2}P_{3/2}(^{2}Π_{3/2}) components has an atom-like character (Hund's case (c) coupling), the SO splitting of higher n states is lower than the atomic value (Hund's case (a) coupling). C. Callegari and W. E. Ernst, Helium Droplets as Nanocryostats for Molecular Spectroscopy - from the Vacuum Ultraviolet to the Microwave Regime, in: Handbook of High-Resolution Spectroscopy, eds. M. Quack and F. Merkt, John Wiley & Sons, Chichester, (2011) F. Lackner, G. Krois, M. Theisen, M. Koch, and W.E. Ernst, Phys. Chem. Chem. Phys., 13, 18781-18788 (2011) F. Lackner, G. Krois, and W.E. Ernst, J. Phys. Chem. Lett., 3, 1404-1408 (2012)

  11. Emergent Kondo Lattice Behavior in Iron-Based Superconductors AFe_{2}As_{2} (A=K, Rb, Cs).

    PubMed

    Wu, Y P; Zhao, D; Wang, A F; Wang, N Z; Xiang, Z J; Luo, X G; Wu, T; Chen, X H

    2016-04-01

    Here, we experimentally study the origin of d-electron heavy fermion (HF) behavior in iron-based superconductors (FeSCs) AFe_{2}As_{2} (A=K, Rb, Cs). Nuclear magnetic resonance on ^{75}As reveals a universal coherent-incoherent crossover with a characteristic temperature T^{*}. Below T^{*}, a so-called "Knight shift anomaly" is first observed in FeSCs, which exhibits a scaling behavior similar to f-electron HF materials. Furthermore, the scaling rule also regulates the manifestation of magnetic fluctuation. These results undoubtedly support an emergent Kondo lattice scenario for the d-electron HF behavior, which qualifies the AFe_{2}As_{2} (A=K, Rb, Cs) as d-electron HF superconductors. PMID:27104721

  12. Emergent Kondo Lattice Behavior in Iron-Based Superconductors A Fe2As2 (A =K , Rb, Cs)

    NASA Astrophysics Data System (ADS)

    Wu, Y. P.; Zhao, D.; Wang, A. F.; Wang, N. Z.; Xiang, Z. J.; Luo, X. G.; Wu, T.; Chen, X. H.

    2016-04-01

    Here, we experimentally study the origin of d -electron heavy fermion (HF) behavior in iron-based superconductors (FeSCs) A Fe2As2 (A =K , Rb, Cs). Nuclear magnetic resonance on 75As reveals a universal coherent-incoherent crossover with a characteristic temperature T*. Below T*, a so-called "Knight shift anomaly" is first observed in FeSCs, which exhibits a scaling behavior similar to f -electron HF materials. Furthermore, the scaling rule also regulates the manifestation of magnetic fluctuation. These results undoubtedly support an emergent Kondo lattice scenario for the d -electron HF behavior, which qualifies the A Fe2As2 (A =K , Rb, Cs) as d -electron HF superconductors.

  13. Analysis of strongly coupled electronic states in diatomic molecules: Low-lying excited states of RbCs

    SciTech Connect

    Bergeman, T.; Fellows, C.E.; Gutterres, R.F.; Amiot, C.

    2003-05-01

    Analysis and assignment of spectra involving the lowest excited states of the heavier alkali-metal atom dimers are complicated by the strong spin-orbit coupling elements. Here we report an analysis of the Fourier-transform spectroscopy data from laser-induced fluorescence of the coupled A {sup 1}{sigma}{sup +} and b {sup 3}{pi} states of RbCs, using the discrete variable representation. Fitted parameters are given and special effects due to strong coupling are discussed.

  14. Temperature-dependent Raman scattering study of the defect pyrochlores RbNbWO6 and CsTaWO6.

    PubMed

    Mączka, M; Knyazev, A V; Majchrowski, A; Hanuza, J; Kojima, S

    2012-05-16

    Lattice dynamics calculations and temperature-dependent Raman scattering experiments were performed on RbNbWO(6) and CsTaWO(6) pyrochlore oxides. The observed bands were assigned to the respective motions of atoms in the unit cell. The spectra showed the presence of additional Raman bands not allowed for by the [Formula: see text] cubic structure. We have shown that these bands appear due to both substitutional disorder in the 16c sites and displacive disorder of the A ions. Raman studies also revealed the presence of an additional 80 cm(-1) band at room temperature for RbNbWO(6), not observed for CsTaWO(6). The presence of this band has been attributed to off-center displacement of the Nb and W ions due to structural phase transition into a tetragonal ferroelectric phase. The temperature evolution of the 80 cm(-1) band intensity revealed that it disappeared at a much higher temperature (about 650 K) than the reported phase transition temperature (about 360 K). This behavior is reminiscent of chemically disordered perovskite ferroelectrics, including relaxor ferroelectrics, and was attributed to the presence of small polar regions with local tetragonal distortion embedded in the paraelectric matrix of the [Formula: see text] structure. PMID:22517168

  15. A full dimensional investigation of infrared spectroscopy of the RbCs dimer using the multi-configuration time-dependent Hartree method

    SciTech Connect

    Wang, Huihui; Yang, Yonggang Xiao, Liantuan; Jia, Suotang

    2013-12-28

    The geometry and infrared absorption spectrum of (RbCs){sub 2} have been studied by full dimensional quantum dynamics simulations. For this purpose, the potential energy and dipole moment surfaces are generated by means of a cluster expansion with all two and three mode correlations, and fitted to analytical expressions with negligible deviations. Accordingly, the ground state (RbCs){sub 2} has a diamond geometry with D{sub 2h} symmetry. The infrared spectrum with frequencies up to 120 cm{sup −1}, exhibits rich details of the fundamentals, overtones, and combination bands; the highest fundamental frequency of (RbCs){sub 2} is only 40.26 cm{sup −1}. The present study unravels important details of the interactions between the widely investigated ultracold RbCs molecules.

  16. Two spatially separated phases in semiconducting Rb0.8Fe1.5S2

    DOE PAGESBeta

    Wang, Meng; Tian, Wei; Valdivia, P.; Chi, Songxue; Bourret-Courchesne, E.; Dai, Pengcheng; Birgeneau, R. J.

    2014-09-26

    We report neutron scattering and transport measurements on semiconducting Rb0.8Fe1.5S2, a compound isostructural and isoelectronic to the well-studied A0.8FeySe2(A = K, Rb, Cs, Tl/K) superconducting systems. Both resistivity and DC susceptibility measurements reveal a magnetic phase transition at T = 275 K. Neutron diffraction studies show that the 275 K transition originates from a phase with rhombic iron vacancy order which exhibits an in-plane stripe antiferromagnetic ordering below 275 K. In addition, the stripe antiferromagnetic phase interdigitates mesoscopically with an ubiquitous phase with √5 x√5 iron vacancy order. This phase has a magnetic transition at TN = 425 K andmore » an iron vacancy order-disorder transition at TS = 600 K. These two different structural phases are closely similar to those observed in the isomorphous Se materials. Based on the close similarities of the in-plane antiferromagnetic structures, moments sizes, and ordering temperatures in semiconducting Rb0.8Fe1.5S2 and K0.81Fe1.58Se2, we argue that the in-plane antiferromagnetic order arises from strong coupling between local moments. Superconductivity, previously observed in the A0.8FeySe2₋ zSz system, is absent in A0.8Fe1.5S2, which has a semiconducting ground state. We discuss the implied relationship between stripe and block antiferromagnetism and superconductivity in these materials as well as a strategy for further investigation.« less

  17. Luminescence properties of the CsSnBr3 phase in metastable Cs4SnBr6

    NASA Astrophysics Data System (ADS)

    Myagkota, S. V.; Savchin, P. V.; Voloshinovskiĭ, A. S.; Demkiv, T. M.; Boĭko, Ya. V.; Vus, R. S.; Demkiv, L. S.

    2008-08-01

    Crystalline materials of the compositions Cs4SnBr6, CsSnBr3, and CsBr-Sn (0.1 mol %) are investigated using x-ray diffraction and luminescent methods. The formation of the CsSnBr3 phase is found to occur in metastable Cs4SnBr6 and CsBr-Sn. It is established that the CsSnBr3 crystalline phase in the Cs4SnBr6 metastable phase is a more stable compound as compared to the CsSnBr3 bulk crystal, which undergoes oxidation and hydration in air.

  18. Precise Measurements of the Masses of Cs, Rb and Na A New Route to the Fine Structure Constant

    NASA Astrophysics Data System (ADS)

    Rainville, Simon; Bradley, Michael P.; Porto, James V.; Thompson, James K.; Pritchard, David E.

    2001-01-01

    We report new values for the atomic masses of the alkali 133Cs, 87Rb, 85Rb, and 23Na with uncertainties ≤ 0.2 ppb. These results, obtained using Penning trap single ion mass spectrometry, are typically two orders of magnitude more accurate than previously measured values. Combined with values of h/m atom from atom interferometry measurements and accurate wavelength measurements for different atoms, these values will lead to new ppb-level determinations of the molar Planck constant N A h and the fine structure constant α. This route to α is based on simple physics. It can potentially achieve the several ppb level of accuracy needed to test the QED determination of α extracted from measurements of the electron g factor. We also demonstrate an electronic cooling technique that cools our detector and ion below the 4 K ambient temperature. This technique improves by about a factor of three our ability to measure the ion's axial motion.

  19. Synthesis and characterization of ASnF{sub 3} (A=Na{sup +}, K{sup +}, Rb{sup +}, Cs{sup +})

    SciTech Connect

    Thao Tran, T.; Shiv Halasyamani, P.

    2014-02-15

    A family of alkali metal tin(II) fluorides, ASnF{sub 3} (A=Na{sup +}, K{sup +}, Rb{sup +}, or Cs{sup +}), has been synthesized through a low temperature solvothermal technique. A fluorine free solvent, methanol, was used in the synthesis. NaSnF{sub 3}, KSnF{sub 3}, and RbSnF{sub 3} have been reported previously; however for RbSnF{sub 3} the reported space group is incorrect. CsSnF{sub 3} is a new alkali tin(II) fluoride, and exhibits a ‘zero-dimensional’ crystal structure with isolated SnF{sub 3}{sup −} anions separated by Cs{sup +} cations. In addition to the synthesis, infrared, UV–vis, thermogravimetric and differential thermal analysis measurements were performed. - Graphical abstract: Ball-and-stick diagrams of CsSnF{sub 3}. Display Omitted - Highlights: • A family of ASnF{sub 3} (A=Na{sup +}, K{sup +}, Rb{sup +} or Cs{sup +}) has been synthesized solvothermally at low temperatures. • Fluorine-free solvent, methanol, was used instead of conventional fluorinating agents. • RbSnF{sub 3} described in the correct space group exhibits infinite chains of corner-sharing SnF{sub 4} polyhedra. • New CsSnF{sub 3} exhibits a ‘zero-dimensional’ crystal structure consisting of isolated SnF{sub 3}{sup −} anionic polyhedra.

  20. Structural, electronic and optical properties of novel carbonate fluorides ABCO{sub 3}F (A=K, Rb, Cs; B=Ca, Sr)

    SciTech Connect

    Narsimha Rao, E.; Appalakondaiah, S.; Yedukondalu, N.; Vaitheeswaran, G.

    2014-04-01

    In the present study, we performed first principles calculations on the electronic and optical properties of layered alkali–alkaline earth carbonate fluorides which attract attention in the domain of nonlinear optics. The calculated lattice parameters and volumes with and without inclusion of van der Waals (vdW) correction methods to standard density functional methods were compared with experiments. We observed that vdW interactions are predominant in RbCaCO{sub 3}F and CsCaCO{sub 3}F as compared with other computed compounds. The calculated bulk modulus from single crystal elastic constants reveals that these materials are all relatively harder than the KH{sub 2}PO{sub 4} (KDP) crystal. We also found that these materials are wide band gap insulators as obtained from Tran–Blaha modified Becke–Johnson potential. The linear optical properties such as dielectric function, refractive indices, birefringence and absorption spectra are presented. Finally, the calculated birefringence values indicate that these crystals could be promising for producing phase matching in the deep ultra-violet region. - Graphical abstract: The co- and anti-parallel alignment of CO{sub 3} groups leads to larger and smaller SHG coefficients in (a) KCaCO{sub 3}F, (b) KSrCO{sub 3}F, (c) RbSrCO{sub 3}F, (d) RbCaCO{sub 3}F, and (e) CsCaCO{sub 3}F. - Highlights: • Effect of van der Waals interactions on structural properties. • Single-crystalline elastic constants and mechanical stability. • Electronic properties. • Linear optical properties. • Comparison of present computed compounds with other well known materials in non-linear optical materials.

  1. Strain-Driven Approach to Quantum Criticality in A Fe2 As2 with A =K , Rb, and Cs

    NASA Astrophysics Data System (ADS)

    Eilers, Felix; Grube, Kai; Zocco, Diego A.; Wolf, Thomas; Merz, Michael; Schweiss, Peter; Heid, Rolf; Eder, Robert; Yu, Rong; Zhu, Jian-Xin; Si, Qimiao; Shibauchi, Takasada; Löhneysen, Hilbert v.

    2016-06-01

    The iron-based superconductors A Fe2 As2 with A =K , Rb, Cs exhibit large Sommerfeld coefficients approaching those of heavy-fermion systems. We have investigated the magnetostriction and thermal expansion of this series to shed light on this unusual behavior. Quantum oscillations of the magnetostriction allow identifying the band-specific quasiparticle masses which by far exceed the band-structure derived masses. The divergence of the Grüneisen ratio derived from thermal expansion indicates that with increasing volume along the series a quantum critical point is approached. The critical fluctuations responsible for the enhancement of the quasiparticle masses appear to weaken the superconducting state.

  2. Strain-Driven Approach to Quantum Criticality in AFe_{2}As_{2} with A=K, Rb, and Cs.

    PubMed

    Eilers, Felix; Grube, Kai; Zocco, Diego A; Wolf, Thomas; Merz, Michael; Schweiss, Peter; Heid, Rolf; Eder, Robert; Yu, Rong; Zhu, Jian-Xin; Si, Qimiao; Shibauchi, Takasada; Löhneysen, Hilbert V

    2016-06-10

    The iron-based superconductors AFe_{2}As_{2} with A=K, Rb, Cs exhibit large Sommerfeld coefficients approaching those of heavy-fermion systems. We have investigated the magnetostriction and thermal expansion of this series to shed light on this unusual behavior. Quantum oscillations of the magnetostriction allow identifying the band-specific quasiparticle masses which by far exceed the band-structure derived masses. The divergence of the Grüneisen ratio derived from thermal expansion indicates that with increasing volume along the series a quantum critical point is approached. The critical fluctuations responsible for the enhancement of the quasiparticle masses appear to weaken the superconducting state. PMID:27341252

  3. Interaction potentials of LiH, NaH, KH, RbH, and CsH

    NASA Astrophysics Data System (ADS)

    Geum, N.; Jeung, G.-H.; Derevianko, A.; Côté, R.; Dalgarno, A.

    2001-10-01

    Quantum-mechanical calculations of the potential energy curves of the singlet and triplet states of LiH, NaH, KH, RbH, and CsH formed by the approach of ground state alkali-metal atoms and hydrogen atoms are presented. Precise values are determined for the coefficients of the van der Waals interaction and estimates are made of the contribution of the exchange interaction at large distances. Together with empirical data, they are used to assess and improve the accuracy of the ab initio potentials.

  4. On the stereochemical inertness of the auride lone pair: ab initio studies of AAu (A = K, Rb, Cs).

    PubMed

    Miao, Maosheng; Brgoch, Jakoah; Krishnapriyan, Aditi; Goldman, Abby; Kurzman, Joshua A; Seshadri, Ram

    2013-07-15

    The "lone" 6s electron pair often plays a key role in determining the structure and physical properties of compounds containing sixth-row elements in their lower oxidation states: Tl(+), Pb(2+), and Bi(3+) with the [Xe]4f(14)5d(10)6s(2) electronic configuration. The lone pairs on these ions are associated with reduced structural symmetries, including ferroelectric instabilities and other important phenomena. Here we consider the isoelectronic auride Au(-) ion with the [Xe]4f(14)5d(10)6s(2) electronic configuration. Ab initio density functional theory methods are employed to probe the effect of the 6s lone pair in alkali-metal aurides (KAu, RbAu, and CsAu) with the CsCl structure. The dielectric constants, Born effective charges, and structural instabilities suggest that the 6s lone pair on the Au(-) anion is stereochemically inert to minor mechanical and electrical perturbation. Pressures greater than 14 GPa, however, lead to reorganization of the electronic structure of CsAu and activate lone-pair involvement and Au-Au interactions in bonding, resulting in a transformation from the cubic CsCl structure type to an orthorhombic Cmcm structure featuring zigzag Au-Au chains. PMID:23822069

  5. Production of rovibronic ground-state 85 Rb133 Cs molecules via photoassociation to Ω = 1 states

    NASA Astrophysics Data System (ADS)

    Shimasaki, Toshihiko; Kim, Jin Tae; Demille, David

    2016-05-01

    We have extensively investigated short-range photoassociation (PA) to the (2) 3Π1 , (2) 1Π1 , and (3) 3Σ1+ states of 85 Rb133 Cs in the region between 11650 cm-1 and 12100 cm-1, where strong mixing between triplet and singlet states is expected. In contrast to the previously observed two-photon cascade decay from the (2) 3Π0 states, here we observe that the PA excited states can directly decay to the rovibronic ground state X1Σ+(v = 0 , J = 0) by a one-photon transition. We have observed rich hyperfine structures of the PA states, which were unresolved in previous cold beam experiments in the same region. Based on the analysis of vibrational and rotational branching ratios in the decay process to the X1Σ+ state, we will discuss the molecule production rate in comparison with that for PA to the (2) 3Π0 states. We will also report on a similar study of PA to the B1 Π and (2) 3Σ1+ states of 85 Rb133 Cs, which also produce the rovibronic ground state X1Σ+(v = 0 , J = 0) via direct one-photon decay.

  6. Independent cross sections of Na, K, Rb, Cs, and Fr isotopes produced in Ta and U targets bombarded by /sup 12/C ions up to 77 MeV/nucleon

    SciTech Connect

    de Saint Simon, M.; Haan, S.; Audi, G.; Coc, A.; Epherre, M.; Guimbal, P.; Langevin, M.; Mueller, A.C.; Thibault, C.; Touchard, F.

    1982-12-01

    Isotopic distribution measurements for Na, K, Rb, Cs, and Fr in the reactions /sup 181/Ta(/sup 12/C,X )Na,K,Rb,Cs and /sup 238/U(/sup 12/C,X )Na,K,Rb,Cs,Fr at different energies E = 13, 27, and 77 MeV/nucleon are reported. The independently observed yields of Rb and Cs show an important contribution for neutron-deficient nuclei. The U target shows very broad isotopic distributions which may be understood as a sum of two components. The results are compared to those obtained by nuclear reactions induced by protons over a wide energy range.

  7. About the mechanism for paramagnetic centers formation under the radiolysis of RbNO3 and CsNO3 crystals

    NASA Astrophysics Data System (ADS)

    Anan'ev, V.; Pak, V.

    2014-05-01

    The accumulation of paramagnetic centers - NO2rad and Orad - in RbNO3 and CsNO3 crystals under γ-irradiation at 310 K and their thermal stability has been studied. The values of the initial radiation chemical yield of NO2rad were calculated to be ∼2.5 × 10-2 (100 eV)-1 in both nitrates. These values for Orad - are equal to 0.05 and 0.38 (100 eV)-1 for RbNO3 and CsNO3, respectively. The heating of irradiated crystals results in the decay of NO2rad and Orad - centers with simultaneously appearance of the ozonide ion. The mechanism for paramagnetic centers formation under γ-irradiation of RbNO3 and CsNO3 crystals has been discussed.

  8. SUMOylation of Rb enhances its binding with CDK2 and phosphorylation at early G1 phase

    PubMed Central

    Meng, Fengxi; Qian, Jiang; Yue, Han; Li, Xiaofeng; Xue, Kang

    2016-01-01

    ABSTRACT Retinoblastoma protein (Rb) is a prototypical tumor suppressor that is vital to the negative regulation of the cell cycle and tumor progression. Hypo-phosphorylated Rb is associated with G0/G1 arrest by suppressing E2F transcription factor activity, whereas Rb hyper-phosphorylation allows E2F release and cell cycle progression from G0/G1 to S phase. However, the factors that regulate cyclin-dependent protein kinase (CDK)-dependent hyper-phosphorylation of Rb during the cell cycle remain obscure. In this study, we show that throughout the cell cycle, Rb is specifically small ubiquitin-like modifier (SUMO)ylated at early G1 phase. SUMOylation of Rb stimulates its phosphorylation level by recruiting a SUMO-interaction motif (SIM)-containing kinase CDK2, leading to Rb hyper-phosphorylation and E2F-1 release. In contrast, a SUMO-deficient Rb mutant results in reduced SUMOylation and phosphorylation, weakened CDK2 binding, and attenuated E2F-1 sequestration. Furthermore, we reveal that Rb SUMOylation is required for cell proliferation. Therefore, our study describes a novel mechanism that regulates Rb phosphorylation during cell cycle progression. PMID:27163259

  9. SUMOylation of Rb enhances its binding with CDK2 and phosphorylation at early G1 phase.

    PubMed

    Meng, Fengxi; Qian, Jiang; Yue, Han; Li, Xiaofeng; Xue, Kang

    2016-07-01

    Retinoblastoma protein (Rb) is a prototypical tumor suppressor that is vital to the negative regulation of the cell cycle and tumor progression. Hypo-phosphorylated Rb is associated with G0/G1 arrest by suppressing E2F transcription factor activity, whereas Rb hyper-phosphorylation allows E2F release and cell cycle progression from G0/G1 to S phase. However, the factors that regulate cyclin-dependent protein kinase (CDK)-dependent hyper-phosphorylation of Rb during the cell cycle remain obscure. In this study, we show that throughout the cell cycle, Rb is specifically small ubiquitin-like modifier (SUMO)ylated at early G1 phase. SUMOylation of Rb stimulates its phosphorylation level by recruiting a SUMO-interaction motif (SIM)-containing kinase CDK2, leading to Rb hyper-phosphorylation and E2F-1 release. In contrast, a SUMO-deficient Rb mutant results in reduced SUMOylation and phosphorylation, weakened CDK2 binding, and attenuated E2F-1 sequestration. Furthermore, we reveal that Rb SUMOylation is required for cell proliferation. Therefore, our study describes a novel mechanism that regulates Rb phosphorylation during cell cycle progression. PMID:27163259

  10. Zirconium bromide cluster chemistry. A new tunnel structure in A{sub 5}Zr{sub 6}Br{sub 15}Be (A = Rb, Cs)

    SciTech Connect

    Qi, Ru-Yi; Corbett, J.D.

    1995-03-29

    Reactions in the ABr-ZrBr{sub 4}-Be systems (A = Cs, Rb) at {approximately}850 {degree}C yield phases with a new tunnel structure constructed from a [Zr{sub 6}(Be)Br{sub 12}]Br{sub 6/3} network. Crystal refinements are given for hexagonal Rb{sub 5.0(1)}Zr{sub 6}Br{sub 15}Be (P6{sub 3}22, Z = 2, a = 13.009(1{angstrom}, c = 12.060(1) {angstrom}, R/R{sub w} = 4.4/4.8%)) and Cs{sub 4.60(8)}Zr{sub 6}Br{sub 15}Be (P6{sub 3}, Z = 2, a = 13.105(1) {angstrom}, c = 12.156(1) {angstrom}, R/R{sub w} = 4.93/3.5%). The boride also exists in the rubidium system. The alkali-metal cations all exhibit fractional occupancies, most being located within or on the walls of the tunnels defined by the bridged cluster array, some with only three close bromine neighbors. Some two-site disorder appears in the rubidium structure (and persists in a marginal refinement of it in P6{sub 3}), while this problem is absent in the cesium compound refinement in the lower symmetry. These characteristics are common in cluster network structures containing larger cations. The formation of 16-e clusters is achieved even with the limited binding of some cations, the cesium salt showing only temperature-independent paramagnetism. This structure type defines a new, fifth type of a M{sub 6}X{sub 12}X{sub 6/2} network.

  11. Atomistic bond relaxation, energy entrapment, and electron polarization of the RbN and CsN clusters (N ≤ 58).

    PubMed

    Guo, Yongling; Bo, Maolin; Wang, Yan; Liu, Yonghui; Huang, Yongli; Sun, Chang Q

    2015-11-11

    We systematically examined the effect of atomic undercoordination on the performance of bonds and electrons of Rb and Cs atomic clusters and their solid skins using a combination of photoelectron spectrometric analysis and density functional theory calculations. Results show that atomic coordination number reduction shortens the bonds by up to 30% for the Rb13 and Cs13 clusters, which densifies the local electrons and entraps their binding energies. Consistency between predictions and observations revealed that the Rb 4p level shifts from 13.654 eV for an isolated atom to a bulk value of 14.940 eV and the Cs 5p level shifts from 10.284 to 11.830 eV upon bulk formation. Such core-electron densification and entrapment polarize the valence charge from the inner to the outermost layer of skins, which perturbs the local Hamiltonian and hence dictates the unusual behavior of the Rb and Cs solid skins and nanocrystals. PMID:26507096

  12. Phase-modulated electronic wave packet interferometry reveals high resolution spectra of free Rb atoms and Rb*He molecules.

    PubMed

    Bruder, Lukas; Mudrich, Marcel; Stienkemeier, Frank

    2015-10-01

    Phase-modulated wave packet interferometry is combined with mass-resolved photoion detection to investigate rubidium atoms attached to helium nanodroplets in a molecular beam experiment. The spectra of atomic Rb electronic states show a vastly enhanced sensitivity and spectral resolution when compared to conventional pump-probe wave packet interferometry. Furthermore, the formation of Rb*He exciplex molecules is probed and for the first time a fully resolved vibrational spectrum for transitions between the lowest excited 5Π3/2 and the high-lying electronic states 2(2)Π, 4(2)Δ, 6(2)Σ is obtained and compared to theory. The feasibility of applying coherent multidimensional spectroscopy to dilute cold gas phase samples is demonstrated in these experiments. PMID:26309123

  13. Role of acentric displacements on the crystal structure and second-harmonic generating properties of RbPbCO3F and CsPbCO3F.

    PubMed

    Tran, T Thao; Halasyamani, P Shiv; Rondinelli, James M

    2014-06-16

    Two lead fluorocarbonates, RbPbCO3F and CsPbCO3F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO3F and CsPbCO3F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO6F2 polyhedra. For RbPbCO3F, infrared and ultraviolet-visible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO3F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6m2 (crystal class 6m2). Powder second-harmonic generation (SHG) measurements on RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 × α-SiO2, respectively. Charge constants d33 of approximately 72 and 94 pm/V were obtained for RbPbCO3F and CsPbCO3F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO6F2 polyhedra, because of the even-odd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb(2+). The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates. PMID:24867361

  14. Role of Acentric Displacements on the Crystal Structure and Second-Harmonic Generating Properties of RbPbCO3F and CsPbCO3F

    PubMed Central

    2015-01-01

    Two lead fluorocarbonates, RbPbCO3F and CsPbCO3F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO3F and CsPbCO3F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO6F2 polyhedra. For RbPbCO3F, infrared and ultraviolet–visible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO3F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6̅m2 (crystal class 6̅m2). Powder second-harmonic generation (SHG) measurements on RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 × α-SiO2, respectively. Charge constants d33 of approximately 72 and 94 pm/V were obtained for RbPbCO3F and CsPbCO3F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO6F2 polyhedra, because of the even–odd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb2+. The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates. PMID:24867361

  15. Scattering parameters for cold Li-Rb and Na-Rb collisions derived from variable phase theory

    SciTech Connect

    Ouerdane, H.; Jamieson, M.J.

    2004-08-01

    We show how the scattering phase shift, the s-wave scattering length, and the p-wave scattering volume can be obtained from Riccati equations derived in variable phase theory. We find general expressions that provide upper and lower bounds for the scattering length and the scattering volume. We show how, in the framework of the variable phase method, Levinson's theorem yields the number of bound states supported by a potential. We report results from a study of the heteronuclear alkali-metal dimers NaRb and LiRb. We consider ab initio molecular potentials for the X {sup 1}{sigma}{sup +} and a {sup 3}{sigma}{sup +} states of both dimers and compare and discuss results obtained from experimentally based X {sup 1}{sigma}{sup +} and a {sup 3}{sigma}{sup +} potentials of NaRb. We explore the mass dependence of the scattering data by considering all isotopomers and we calculate the numbers of bound states supported by the molecular potentials for each isotopomer.

  16. Low-lying {sup 3}P{sup o} and {sup 3}S{sup e} states of Rb{sup -}, Cs{sup -}, and Fr{sup -}

    SciTech Connect

    Bahrim, C.; Thumm, U.

    2000-02-01

    Our Dirac R-matrix calculations suggest that none of the heavy alkali-metal negative ions, Rb, Cs, and Fr, has an excited bound state. Their lowest excited state appears to be a multiplet of {sup 3}P{sub J}{sup o}-shape resonances, the J=1 component of which was recently observed in photodetachment experiments on Cs{sup -}. We analyze these {sup 3}P{sub J}{sup o} and the {sup 3}S{sup e} excited negative ion states in partial and converged total scattering cross sections for slow electrons with incident kinetic energies below 120 meV. Our results are in excellent agreement with available experimental data. We also propose a new value for the electron affinity of Fr, provide the scattering length for electronic collisions with Rb, Cs, and Fr, and discuss the nuclear charge dependence of relativistic effects in the resonance profiles. (c) 2000 The American Physical Society.

  17. Syntheses, structures and magnetic properties of the alkali oxonickelates(I) A3NiO2 (A = K, Rb, Cs)

    NASA Astrophysics Data System (ADS)

    Đuriš, Katarina; Magdysyuk, Oxana V.; Jansen, Martin

    2012-10-01

    New oxonickelates(I), Rb3NiO2 and Cs3NiO2, were prepared via the azide/nitrate route, starting from stoichiometric mixtures of azides, nitrates and NiO as precursors. The mixtures were heated steadily in a controlled heating regime up to 723 K and annealed at this temperature for 50 h (30 h for cesium compound) in specially designed containers with silver inlays. The crystal structures of Rb3NiO2 and Cs3NiO2 were solved and refined by X-ray powder methods. Room temperature α-Rb3NiO2 (P41212, Z = 4, a = 6.2651(2) Å, b = 14.7438(3) Å; Rwp = 6.30%) and high temperature β-Rb3NiO2 (at 523 K P42/mnm, Z = 2, a = 6.2750(2) Å, b = 7.5088(3) Å; Rwp = 7.85%) were found to be isostructural to room and high temperature α- and β-K3NiO2, respectively. Cs3NiO2 crystallizes at room temperature isostructural with the β-K3NiO2 (P42/mnm, Z = 2, a = 6.4336(3) Å, b = 8.0844(4) Å; Rwp = 5.21%). A3NiO2 (A = K, Rb, Cs) are paramagnetic in the whole temperature range investigated. The magnetic susceptibility data have been evaluated by the Curie-Weiss law, where the calculated magnetic moments are as expected for a d9 system (μ = 1.73-2.20μB). Negative values of Weiss constants are indicative for antiferromagnetic interactions in this family of compounds.

  18. New alkali metal diphosphates how materials to preserve the security of the environment: CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7) synthesis and crystal structure determination

    NASA Astrophysics Data System (ADS)

    Chernyatieva, Anastasiya; Filatova, Alyona; Spiridonova, Dariya; Krivovichev, Sergey

    2013-04-01

    In this work we describe preliminary results of the synthesis and of a crystal-chemical study of synthetic phosphates with transition metals. Due to the increasing requirements for environmental safety specialists from various industries, we are searching for sustainable forms of immobilization of hazardous waste during storage. We are also developing a component-based waste for new materials. In our continued exploratory synthesis of compounds containing transition-metals, we were able to produce the new diphosphate phases CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7). A crystal chemical study has allowed us to identify new phosphates. Crystals of CsNaCu(P2O7) (Phase 1) is orthorhombic, crystallizes in space group Pmn21, with a = 5.147(8), b = 15.126(2), c = 9.717(2) Å, V = 756.20 Å3, R1 = 0.066 and Rb2Cu(P2O7) (Phase 2) is orthorhombic as well, crystallizes in space group Pmcn, with a = 5.183(8), b = 10.096(1), c = 15.146(3) Å, V = 793.55 Å3, R1 = 0.063, they have been obtained by high-temperature reaction of RbNO3, CsNO3, Cu(NO3)2, NaOH and (NH4)4P2O7. Synthetic crystals of the phosphate of copper and rubidium were studied in detail by us on the structures of Rb2Cu(P2O7) and Rb2Cu3(P2O7)2 - new alkali metal copper diphosphates (CHERNYATIEVA et al., 2008). Here we report the synthesis, the structure and the properties of the title compounds and we compare these phases with the previously discovered K2CuP2O7 (ELMAADI et al., 1995) and CsNaMnP2O7 (HUANG et al., 1998). These structures crystallize in other space groups, although their structures are also based on 2-D layers, formed by P2O7 groups combined with polyhedra of the transition metals (CHERNYATIEVA et al., 2012). A crystal chemical study has allowed us to identify even new diphosphates CsNaCu(P2O7) (Phase 3). Crystals of CsNaCoP2O7 is monoclinic, space group P 21/n, with a = 7,424(2), b = 7,648(1), c = 12,931(3)Å, β = 90,71(2)° , V = 734.2(3) Å3 and R1 = 0.060. The structure is based framework of Co

  19. Measurement of the binding energy of ultracold 87Rb133Cs molecules using an offset-free optical frequency comb

    NASA Astrophysics Data System (ADS)

    Molony, Peter K.; Kumar, Avinash; Gregory, Philip D.; Kliese, Russell; Puppe, Thomas; Le Sueur, C. Ruth; Aldegunde, Jesus; Hutson, Jeremy M.; Cornish, Simon L.

    2016-08-01

    We report the binding energy of 87Rb133Cs molecules in their rovibrational ground state measured using an offset-free optical frequency comb based on difference frequency generation technology. We create molecules in the absolute ground state using stimulated Raman adiabatic passage (STIRAP) with a transfer efficiency of 88%. By measuring the absolute frequencies of our STIRAP lasers, we find the energy-level difference from an initial weakly bound Feshbach state to the rovibrational ground state with a resolution of ˜5 kHz over an energy-level difference of more than 114 T Hz ; this lets us discern the hyperfine splitting of the ground state. Combined with theoretical models of the Feshbach-state binding energies and ground-state hyperfine structure, we determine a zero-field binding energy of h ×114 268 135.24 (4 )(3 )M Hz . To our knowledge, this is the most accurate determination to date of the dissociation energy of a molecule.

  20. Shape resonances in ground-state diatomic molecules: General trends and the example of RbCs

    SciTech Connect

    Londono, B. E.; Mahecha, J. E.; Luc-Koenig, E.; Crubellier, A.

    2010-07-15

    The presence of shape resonances due to tunneling through the centrifugal barrier modifies strongly the dynamics of cold atom scattering. As shown on the example of the ground and lowest triplet electronic states of the {sup 85}Rb{sup 133}Cs molecule, the crucial parameter is, as usual for cold collisions, the scattering length. A general description of shape resonances of diatomic molecules is given from three simple single channel asymptotic models, whose respective performances are discussed. The first model, which consists of a R{sup -6} potential limited at short range by a repulsive wall, positioned to reproduce the s-wave scattering length, accounts satisfactorily for the main system-independent properties of shape resonances. Introduction in the model of energy- and angular-momentum-dependent nodal lines specific to the inner part of the potential greatly improves its efficiency. When the energy and angular momentum dependence of the nodal lines cannot be deduced from full potential calculations or from experiment, a rough, but universal, estimate of these properties is obtained by extending the R{sup -6} behavior of the potential up to the origin.

  1. Evolution of quasiparticle excitations with enhanced electron correlations in superconducting A Fe2As2 (A =K , Rb, and Cs)

    NASA Astrophysics Data System (ADS)

    Mizukami, Y.; Kawamoto, Y.; Shimoyama, Y.; Kurata, S.; Ikeda, H.; Wolf, T.; Zocco, D. A.; Grube, K.; Löhneysen, H. v.; Matsuda, Y.; Shibauchi, T.

    2016-07-01

    In the heavily hole-doped iron-based superconductors A Fe2As2 (A =K , Rb, and Cs), the electron effective mass increases rapidly with alkali-ion radius. To study the superconducting gap structure in this series, we measure the in-plane London penetration depth λa b(T ) in clean crystals of A Fe2As2 down to low temperature T ˜0.1 K. In KFe2As2 , the superfluid stiffness ρsa b(T ) =λab 2(0 ) /λab 2(T ) at low temperatures can be accounted for by the strongly band-dependent multiple gaps reported recently. Although the λa b(T ) in all systems exhibits similar nonexponential temperature dependence indicating nodes or small minima in the gap, we find that the quasiparticle excitations at low temperatures show a systematic suppression with increasing alkali-ion radius. A possible origin of such evolution of low-energy excitations is discussed in terms of the momentum-dependent effect of enhanced quasiparticle mass near a quantum critical point.

  2. Optically isotropy in scintillator host compounds M{sub 2}LaCl{sub 5} (M=Rb, and Cs): Ab-initio study

    SciTech Connect

    Shwetha, G.; Kanchana, V.; Vaitheeswaran, G.

    2015-06-24

    Full potential linearized augmented plane wave method (FP-LAPW) has been used to calculate the electronic structure and optical properties of high light output scintillator host compounds M{sub 2}LaCl{sub 5} (M=Rb, and Cs) with in the Tran Blaha modified Becke Johnson (TB-mBJ) potential. These are wide band gap materials with the band gap of 4.75, and 4.72 eV for Rb{sub 2}LaCl{sub 5}, and Cs{sub 2}LaCl{sub 5} respectively. From the calculated optical properties of these compounds, we find these compounds to be optically isotropic, though they are structurally anisotropic, which is an important criteria for the ceramic scintillators.

  3. Synthesis and structural characterization of the new clathrates K8Cd4Ge42, Rb8Cd4Ge42, and Cs8Cd4Ge42

    DOE PAGESBeta

    Schafer, Marion; Bobev, Svilen

    2016-03-25

    This paper presents results from our exploratory work in the systems K-Cd-Ge, Rb-Cd-Ge, and Cs-Cd-Ge, which yielded the novel type-I clathrates with refined compositions K8Cd3.77(7)Ge42.23, Rb8Cd3.65(7)Ge42.35, and Cs7.80(1)Cd3.65(6)Ge42.35. The three compounds represent rare examples of clathrates of germanium with the alkali metals, where a d10 element substitutes a group 14 element. The three structures, established by single-crystal X-ray diffraction, indicate that the framework-building Ge atoms are randomly substituted by Cd atoms on only one of the three possible crystallographic sites. Furthermore, this and several other details of the crystal chemistry are elaborated.

  4. A CASPT2 study of the spectral shift of the resonance emission lines of Rb and Cs embedded in liquid He

    NASA Astrophysics Data System (ADS)

    Modesto-Costa, Lucas; Mukherjee, Prasanta Kumar; Canuto, Sylvio

    2016-07-01

    The emission line shifts of the resonance transitions (s ← p) of Rb and Cs embedded in liquid He environment have been estimated using CASPT2 with quadruple-zeta basis sets. The liquid He environment has been approximated by a spherically symmetric model cluster, with 14 He atoms placed in equidistant positions from the central alkali atom. The emission line for the D1 transition is found to be blue shifted. The shift is estimated to be -1.2 to -1.8 nm for Rb and -2.2 to -2.6 nm for Cs, in very good agreement with the experimental estimates of -1.2 nm and -2.1 nm respectively obtained in liquid He.

  5. Optically isotropy in scintillator host compounds M2LaCl5 (M=Rb, and Cs): Ab-initio study

    NASA Astrophysics Data System (ADS)

    Shwetha, G.; Vaitheeswaran, G.; Kanchana, V.

    2015-06-01

    Full potential linearized augmented plane wave method (FP-LAPW) has been used to calculate the electronic structure and optical properties of high light output scintillator host compounds M2LaCl5 (M=Rb, and Cs) with in the Tran Blaha modified Becke Johnson (TB-mBJ) potential. These are wide band gap materials with the band gap of 4.75, and 4.72 eV for Rb2LaCl5, and Cs2LaCl5 respectively. From the calculated optical properties of these compounds, we find these compounds to be optically isotropic, though they are structurally anisotropic, which is an important criteria for the ceramic scintillators.

  6. The determination of potential energy curve and dipole moment of the (5)0(+) electronic state of (85)Rb(133)Cs molecule by high resolution photoassociation spectroscopy.

    PubMed

    Yuan, Jinpeng; Zhao, Yanting; Ji, Zhonghua; Li, Zhonghao; Kim, Jin-Tae; Xiao, Liantuan; Jia, Suotang

    2015-12-14

    We present the formation of ultracold (85)Rb(133)Cs molecules in the (5)0(+) electronic state by photoassociation and their detection via resonance-enhanced two-photon ionization. Up to v = 47 vibrational levels including the lowest v = 0 vibrational and lowest J = 0 levels are identified with rotationally resolved high resolution photoassociation spectra. Precise Dunham coefficients are determined for the (5)0(+) state with high accuracy, then the Rydberg-Klein-Rees potential energy curve is derived. The electric dipole moments with respect to the vibrational numbers of the (5)0(+) electronic state of (85)Rb(133)Cs molecule are also measured in the range between 1.9 and 4.8 D. These comprehensive studies on previously unobserved rovibrational levels of the (5)0(+) state are helpful to understand the molecular structure and discover suitable transition pathways for transferring ultracold atoms to deeply bound rovibrational levels of the electronic ground state. PMID:26671380

  7. The determination of potential energy curve and dipole moment of the (5)0+ electronic state of 85Rb133Cs molecule by high resolution photoassociation spectroscopy

    NASA Astrophysics Data System (ADS)

    Yuan, Jinpeng; Zhao, Yanting; Ji, Zhonghua; Li, Zhonghao; Kim, Jin-Tae; Xiao, Liantuan; Jia, Suotang

    2015-12-01

    We present the formation of ultracold 85Rb133Cs molecules in the (5)0+ electronic state by photoassociation and their detection via resonance-enhanced two-photon ionization. Up to v = 47 vibrational levels including the lowest v = 0 vibrational and lowest J = 0 levels are identified with rotationally resolved high resolution photoassociation spectra. Precise Dunham coefficients are determined for the (5)0+ state with high accuracy, then the Rydberg-Klein-Rees potential energy curve is derived. The electric dipole moments with respect to the vibrational numbers of the (5)0+ electronic state of 85Rb133Cs molecule are also measured in the range between 1.9 and 4.8 D. These comprehensive studies on previously unobserved rovibrational levels of the (5)0+ state are helpful to understand the molecular structure and discover suitable transition pathways for transferring ultracold atoms to deeply bound rovibrational levels of the electronic ground state.

  8. Schottky-barrier and interface formation of Cs/GaSb(110) and Rb/GaSb(110) at room temperature

    NASA Astrophysics Data System (ADS)

    Schirm, K. M.; Soukiassian, P.; Mangat, P. S.; Soonckindt, L.

    1994-02-01

    The Schottky-barrier and interface formation of Cs/GaSb(110) and Rb/GaSb(110) at room temperature are investigated by soft-x-ray core level photoemission spectroscopy using synchrotron radiation. A large splitting (0.9 eV) is found at the Cs 4d core level and indicates two different adsorption sites (having a large difference in ionicity) for the alkali-metal atoms on the GaSb(110) surface with bonding to both cation and anion. The large Fermi-level overshootings observed at very low alkali-metal coverages [0.03 monolayer (ML) Cs or Rb] for the p-type GaSb(110) samples are directly related to the specific donor character of alkali-metal atoms with charge transfer into the empty Ga dangling bond. The unique room-temperature growth properties of alkali metals are also likely to be of relevance. Further Cs or Rb deposition is found to be highly disruptive with large reactive components at Sb 4d but also Ga 3d core levels and a higher reactivity for the smaller alkali metal (Rb). Interestingly, this interface reactivity, which results from surface defects, is also significantly higher for p-type than for n-type samples, suggesting that the nature of the doping might play some role in the interface chemistry. The final Fermi-level pinning position for both p- and n-type GaSb(110) is already achieved at an alkali-metal coverage of about 0.3 ML, corresponding to significant changes in the mode of growth and to the threshold of surface disruption. This pinning position is located at about 0.1 eV above the valence-band maximum, in agreement with a defect acceptor state model.

  9. Triple-barrel structure of inwardly rectifying K+ channels revealed by Cs+ and Rb+ block in guinea-pig heart cells.

    PubMed

    Matsuda, H; Matsuura, H; Noma, A

    1989-06-01

    1. The hypothesis that the inwardly rectifying K+ channel consists of a triple-barrel structure was investigated. Inward currents were recorded under the blocking effects of external Cs+ or Rb+ in the cell-attached configuration of the patch-clamp technique using single ventricular cells enzymatically isolated from guinea-pig hearts. 2. Cs+ (10-100 microM) or Rb+ (20-100 microM) added to the 150 mM-K+ pipette solution induced rapid open-blocked transitions in the inward open-channel currents. In about 20% of experiments the inward current showed two intermediate current levels equally spaced between the unit amplitude and the zero-conductance level. The current fluctuated between these four levels. In the remaining experiments no obvious sublevels were observed except spontaneous ones, whose amplitudes were not always equal to one-third or two-thirds of the unit amplitude. 3. In experiments showing sublevels, the probability that the open-channel current stayed at each level was measured at various concentrations of blockers and membrane potentials. In both Cs+ and Rb+ block, the distribution of the current levels showed reasonable agreement with the binomial theorem. This finding suggests that the inwardly rectifying K+ channel is composed of three equally conductive subunits and each subunit is independently blocked by Cs+ or Rb+. 4. The dwell-time histogram in each substate was well fitted with a single-exponential function. On the assumption of the binomial model, the blocking (mu) and unblocking (lambda) rate for Cs+ and Rb+ were calculated. The value of mu was linearly proportional to the concentration of the blocking ion at a given membrane potential and increased with hyperpolarization (e-fold increase with a change of -43.5 mV in the Cs+ block). lambda was almost independent of the concentration of the blocking ion and less dependent on the membrane potential than mu. 5. The open and blocked times were calculated in experiments showing no clear sublevels

  10. Structural, electronic and optical properties of novel carbonate fluorides ABCO3F (A=K, Rb, Cs; B=Ca, Sr)

    NASA Astrophysics Data System (ADS)

    Narsimha Rao, E.; Appalakondaiah, S.; Yedukondalu, N.; Vaitheeswaran, G.

    2014-04-01

    In the present study, we performed first principles calculations on the electronic and optical properties of layered alkali-alkaline earth carbonate fluorides which attract attention in the domain of nonlinear optics. The calculated lattice parameters and volumes with and without inclusion of van der Waals (vdW) correction methods to standard density functional methods were compared with experiments. We observed that vdW interactions are predominant in RbCaCO3F and CsCaCO3F as compared with other computed compounds. The calculated bulk modulus from single crystal elastic constants reveals that these materials are all relatively harder than the KH2PO4 (KDP) crystal. We also found that these materials are wide band gap insulators as obtained from Tran-Blaha modified Becke-Johnson potential. The linear optical properties such as dielectric function, refractive indices, birefringence and absorption spectra are presented. Finally, the calculated birefringence values indicate that these crystals could be promising for producing phase matching in the deep ultra-violet region.

  11. Atomic masses of {sup 6}Li,{sup 23}Na,{sup 39,41}K,{sup 85,87}Rb, and {sup 133}Cs

    SciTech Connect

    Mount, Brianna J.; Redshaw, Matthew; Myers, Edmund G.

    2010-10-15

    The atomic masses of the alkali-metal isotopes {sup 6}Li,{sup 23}Na,{sup 39,41}K,{sup 85,87}Rb, and {sup 133}Cs have been obtained from measurements of cyclotron frequency ratios of pairs of ions simultaneously trapped in a Penning trap. The results, with one standard deviation uncertainty, are: M({sup 6}Li)=6.015 122 887 4(16)u,M({sup 23}Na)=22.989769 282 8(26)u,M({sup 39}K)=38.963 706 485 6(52)u,M({sup 41}K)=40.961 825 257 4(48)u,M({sup 85}Rb)=84.911 789739(9)u,M({sup 87}Rb)=86.909 180 535(10)u, and M({sup 133}Cs)=132.905 451 963(13)u. Our mass of {sup 6}Li yields an improved neutron separation energy for {sup 7}Li of 7251.1014(45) keV.

  12. A combined metal-halide/metal flux synthetic route towards type-I clathrates: crystal structures and thermoelectric properties of A8Al8Si38 (A = K, Rb, and Cs).

    PubMed

    Baran, Volodymyr; Senyshyn, Anatoliy; Karttunen, Antti J; Fischer, Andreas; Scherer, Wolfgang; Raudaschl-Sieber, Gabriele; Fässler, Thomas F

    2014-11-10

    Single-phase samples of the compounds K8Al8Si38 (1), Rb8Al8Si38 (2), and Cs7.9Al7.9Si38.1 (3) were obtained with high crystallinity and in good quantities by using a novel flux method with two different flux materials, such as Al and the respective alkali-metal halide salt (KBr, RbCl, and CsCl). This approach facilitates the removal of the product mixture from the container and also allows convenient extraction of the flux media due to the good solubility of the halide salts in water. The products were analyzed by means of single-crystal X-ray structure determination, powder X-ray and neutron diffraction experiments, (27)Al-MAS NMR spectroscopy measurements, quantum chemical calculations, as well as magnetic and transport measurements (thermal conductivity, electrical resistivity, and Seebeck coefficient). Due to the excellent quality of the neutron diffraction data, the difference between the nuclear scattering factors of silicon and aluminum atoms was sufficient to refine their mixed occupancy at specific sites. The role of variable-range hopping for the interpretation of the resistivity and the Seebeck coefficient is discussed. PMID:25267571

  13. Evaluation of in vivo detection properties of 22Na, 65Zn, 86Rb, 109Cd and 137Cs in plant tissues using real-time radioisotope imaging system

    NASA Astrophysics Data System (ADS)

    Sugita, Ryohei; Kobayashi, Natsuko I.; Hirose, Atsushi; Tanoi, Keitaro; Nakanishi, Tomoko M.

    2014-02-01

    In plant research, radioisotope imaging provides useful information about physiological activities in various tissues and elemental transport between plant organs. To expand the usage of imaging techniques, a new system was developed to visualize beta particles, x-rays and gamma-rays emitted from plant bodies. This real-time radioisotope imaging system (RRIS) visualizes radioactivity after conversion into light with a CsI(Tl) scintillator plate. Herein, the RRIS detection properties of the gamma-ray emitters 22Na, 65Zn, 86Rb, 109Cd and 137Cs were evaluated in comparison with those of radioluminography (RLG) using an imaging plate. The lower quantitative detection limit (Bq mm-2) during a 15 min period ranged from 0.1 to 4, depending on the nuclide, similar to that of RLG. When the quantitative ability to detect radiation from various Arabidopsis tissues was analyzed, the quantitative capability in silique and the thick internode tended to be low. In an EGS5 simulation, beta particles were the greatest contributors to RRIS imaging of 22Na, 86Rb and 137Cs, and low-energy x-rays contributed significantly to 65Zn and 109Cd detection. Thus, both self-absorption and air space between the sample and scintillator surface could impair quantitative RRIS imaging. Despite these issues, RRIS is suggested for quantitative time-course measurements of radionuclide motion within plants.

  14. Unusual centrosymmetric structure of [M(18-crown-6)](+) (M = Rb, Cs and NH4) complexes stabilized in an environment of hexachloridoantimonate(V) anions.

    PubMed

    Ponomarova, Vira V; Rusanova, Julia A; Rusanov, Eduard B; Domasevitch, Konstantin V

    2015-10-01

    In (1,4,7,10,13,16-hexaoxacyclooctadecane)rubidium hexachloridoantimonate(V), [Rb(C12H24O6)][SbCl6], (1), and its isomorphous caesium {(1,4,7,10,13,16-hexaoxacyclooctadecane)caesium hexachloridoantimonate(V), [Cs(C12H24O6)][SbCl6]}, (2), and ammonium {ammonium hexachloridoantimonate(V)-1,4,7,10,13,16-hexaoxacyclooctadecane (1/1), (NH4)[SbCl6]·C12H24O6}, (3), analogues, the hexachloridoantimonate(V) anions and 18-crown-6 molecules reside across -3 axes passing through the Sb atoms and the centroids of the 18-crown-6 groups, both of which coincide with centres of inversion. The Rb(+) [in (1)], Cs(+) [in (2)] and NH4(+) [in (3)] cations are situated inside the cavity of the 18-crown-6 ring; they are situated on -3 axes and are equally disordered about centres of inversion, deviating from the centroid of the 18-crown-6 molecule by 0.4808 (13), 0.9344 (7) and 0.515 (8) Å, respectively. Interaction of the ammonium cation and the 18-crown-6 group is supported by three equivalent hydrogen bonds [N...O = 2.928 (3) Å and N-H...O = 162°]. The centrosymmetric structure of [Cs(18-crown-6)](+), with the large Cs(+) cation approaching the centre of the ligand cavity, is unprecedented and accompanied by unusually short Cs-O bonds [2.939 (2) and 3.091 (2) Å]. For all three compounds, the [M(18-crown-6)](+) cations and [SbCl6](-) anions afford linear stacks along the c axis, with the cationic complexes embedded between pairs of inversion-related anions. PMID:26422213

  15. Structure and superconductivity of (Li1-x Fe x )OHFeSe single crystals grown using A x Fe2-y Se2 (A  =  K, Rb, and Cs) as precursors.

    PubMed

    Yu, G; Zhang, G Y; Ryu, G H; Lin, C T

    2016-01-13

    We present results on the hydrothermal growth of ([Formula: see text])OHFeSe single crystals using floating-zone-grown [Formula: see text] (A  =  K, Rb, and Cs) as precursors. The growth proceeds by the hydrothermal ion exchange of Li/Fe-O-H for K, Rb, and Cs, resulting in a stacking layer of ([Formula: see text])OH sandwiched between the FeSe layers. Optimal growth parameters are achieved using high quality A 0.80Fe1.81Se2 single crystals added to the mixtures of LiOH, H2O, Fe and C(NH2)2Se in an autoclave and subsequently heated to 120 °C for 2 d, to obtain highest quality single crystals. The obtained crystals have lateral dimensions up to centimeters, with the final size related to that of the precursor crystal used. All ([Formula: see text])OHFeSe single crystals show a superconducting transition temperature T c  >  42 K, regardless of the phase of the precursor such as superconducting K0.80Fe1.81Se2 (T c  =  29.31 K) or non-superconducting Rb0.80Fe1.81Se2 or poor-superconducting Cs0.80Fe1.81Se2 (T c  =  28.67 K). The T c and transition width ΔT vary in the obtained single crystals, due to the inhomogeneity of the ionic exchange. X-ray diffraction analysis demonstrates that the 245 insulating phase is absent in the ion-exchanged single crystals, while it is observed in the [Formula: see text] precursors. Comparative studies of the structure, magnetization, and superconductivity on the parent A 0.80Fe1.81Se2 and the ion-exchanged ([Formula: see text])OHFeSe crystals are discussed. A phase diagram including antiferromagnetic spin density wave and superconducting phases is also proposed. PMID:26656943

  16. Structure and superconductivity of (Li1-x Fe x )OHFeSe single crystals grown using A x Fe2-y Se2 (A  =  K, Rb, and Cs) as precursors

    NASA Astrophysics Data System (ADS)

    Yu, G.; Zhang, G. Y.; Ryu, G. H.; Lin, C. T.

    2016-01-01

    We present results on the hydrothermal growth of (\\text{L}{{\\text{i}}1-x}\\text{F}{{\\text{e}}x} )OHFeSe single crystals using floating-zone-grown {{A}x}\\text{F}{{\\text{e}}2-y}\\text{S}{{\\text{e}}2} (A  =  K, Rb, and Cs) as precursors. The growth proceeds by the hydrothermal ion exchange of Li/Fe-O-H for K, Rb, and Cs, resulting in a stacking layer of (\\text{L}{{\\text{i}}1-x}\\text{F}{{\\text{e}}x} )OH sandwiched between the FeSe layers. Optimal growth parameters are achieved using high quality A 0.80Fe1.81Se2 single crystals added to the mixtures of LiOH, H2O, Fe and C(NH2)2Se in an autoclave and subsequently heated to 120 °C for 2 d, to obtain highest quality single crystals. The obtained crystals have lateral dimensions up to centimeters, with the final size related to that of the precursor crystal used. All (\\text{L}{{\\text{i}}1-x}\\text{F}{{\\text{e}}x} )OHFeSe single crystals show a superconducting transition temperature T c  >  42 K, regardless of the phase of the precursor such as superconducting K0.80Fe1.81Se2 (T c  =  29.31 K) or non-superconducting Rb0.80Fe1.81Se2 or poor-superconducting Cs0.80Fe1.81Se2 (T c  =  28.67 K). The T c and transition width ΔT vary in the obtained single crystals, due to the inhomogeneity of the ionic exchange. X-ray diffraction analysis demonstrates that the 245 insulating phase is absent in the ion-exchanged single crystals, while it is observed in the {{A}x}\\text{F}{{\\text{e}}2-y}\\text{S}{{\\text{e}}2} precursors. Comparative studies of the structure, magnetization, and superconductivity on the parent A 0.80Fe1.81Se2 and the ion-exchanged (\\text{L}{{\\text{i}}1-x}\\text{F}{{\\text{e}}x} )OHFeSe crystals are discussed. A phase diagram including antiferromagnetic spin density wave and superconducting phases is also proposed.

  17. The determination of potential energy curve and dipole moment of the (5) 0+ electronic state of 85 Rb133 Cs molecule by high resolution photoassociation spectroscopy

    NASA Astrophysics Data System (ADS)

    Yuan, Jinpeng; Zhao, Yanting; Ji, Zhonghua; Li, Zhonghao; Kim, Jin-Tae; Xiao, Liantuan; Jia, Suotang

    2016-05-01

    The creation and manipulation of ultracold polar molecules have attracted intensive attentions due to their permanent electric dipole moments interacting strongly with an external electric field and with long-range dipole-dipole force, which facilitate applications such as precision measurement, quantum control of cold chemical reactions, and quantum computation. The (5) 0+ state is a good candidate to produce ultracold ground state RbCs molecule through a short-range photoassociation (PA). We present the formation of ultracold 85 Rb133 Cs molecules in the (5) 0+ electronic state by PA and their detection via resonance-enhanced two-photon ionization. Up to v = 47 vibrational levels including the lowest v = 0 and lowest J = 0 levels are identified with high resolution. Precise Dunham coefficients and the Rydberg-Klein-Rees potential energy curve of the (5) 0+ state are determined The electric dipole moments with respect to the vibrational numbers of the (5) 0+ electronic state are also measured in the range between 1.9 and 4.8 D. These comprehensive studies on previously unobserved rovibrational levels of the (5) 0+ state are helpful to understand the molecular structure and discover suitable transition pathways for transferring to the lowest rovibrational level of the ground state.

  18. Effect of Rb2O and Cs2O on Inclusion Removal in 321 Stainless Steels Using Novel Basic Tundish Fluxes

    NASA Astrophysics Data System (ADS)

    Choi, Kyunsuk; Kang, Youngjo; Sohn, Il

    2016-06-01

    Inclusion removal and modification of the 321 stainless steel using Rb2O- and Cs2O-containing novel basic tundish flux has been investigated. The average inclusion diameter was significantly lowered after reaction of the liquid metal with the flux after 45 minutes in an induction furnace set at 1823 K (1550 °C) under an Ar atmosphere. The number of inclusions was also decreased with increased reaction time and the majority of the inherent TiN inclusions were removed after reaction with the proposed novel basic tundish flux. Spinel inclusions were also observed after the reaction, which was due to the reaction of the MgO crucible and the CaO-Al2O3-SiO2-MgO-` x'wt pct R2O flux system at fixed CaO/(Al2O3 + SiO2) of 1.45. The Rb2O and Cs2O seemed to have allowed significant removal of the TiN inclusions due to its ion compensation effect and the supplement of free oxygen ions, while increasing the viscosity of the slag to retain the absorbed inclusions.

  19. Heat capacity, p-T phase diagram, and structure of Rb2KTiOF5

    NASA Astrophysics Data System (ADS)

    Fokina, V. D.; Flerov, I. N.; Molokeev, M. S.; Pogorel'Tsev, E. I.; Bogdanov, E. V.; Krylov, A. S.; Bovina, A. F.; Voronov, V. N.; Laptash, N. M.

    2008-11-01

    Elpasolite Rb2KTiOF5 (space group, Fm bar 3 m, Z = 4) was synthesized using a solid-phase reaction method. The temperature dependences of the heat capacity, the unit cell parameters, the structure, the permittivity, the response to an external pressure, and the Raman spectra were studied. A nonferroelectric phase transition was revealed at T 0 = 215 K; the transition is accompanied by a tetragonal distortion of the unit cell (space group I4/ m, Z = 10) and a change in the entropy (Δ S 0 = Rln8), which is anomalously large for perovskite-like oxyfluorides with atomic cations. The specific features of the mechanism of structure distortion are discussed in combination with the previous experimental data obtained for cryolite (NH4)3TiOF5 and elpasolite Rb2KGaF6.

  20. Microscopic nature of correlations in multiorbital A Fe2As2 (A =K,Rb,Cs) : Hund's coupling versus Coulomb repulsion

    NASA Astrophysics Data System (ADS)

    Backes, Steffen; Jeschke, Harald O.; Valentí, Roser

    2015-11-01

    We investigate via LDA+DMFT (local density approximation combined with dynamical mean field theory) the manifestation of correlation effects in a wide range of binding energies in the hole-doped family of Fe pnictides A Fe2As2 (A =K ,Rb, Cs) as well as the fictitious FrFe2As2 and a -axis stretched CsFe2As2 . This choice of systems allows for a systematic analysis of the interplay of Hund's coupling JH and on-site Coulomb repulsion U in multiorbital Fe pnictides under negative pressure. With increasing ionic size of the alkali metal, we observe a nontrivial change in the iron 3 d hoppings, an increase of orbitally-selective correlations, and the presence of incoherent weight at high binding energies that do not show the typical lower Hubbard-band behavior but rather characteristic features of a Hund's metal. This is especially prominent in a b -stretched CsFe2As2 . We also find that the coherent/incoherent electronic behavior of the systems is, apart from temperature, strongly dependent on JH, and we provide estimates of the coherence scale T*. We discuss these results in the framework of reported experimental observations.

  1. Extended Fourier-transform spectroscopy studies and deperturbation analysis of the spin-orbit coupled A1Σ+ and b3Π states in RbCs.

    PubMed

    Kruzins, A; Alps, K; Docenko, O; Klincare, I; Tamanis, M; Ferber, R; Pazyuk, E A; Stolyarov, A V

    2014-11-14

    The article presents a study of the strongly spin-orbit coupled singlet A(1)Σ(+) and triplet b(3)Π states of the RbCs molecule, which provide an efficient optical path to transfer ultracold molecules to their rovibrational ground state. Fourier-transform A(1)Σ(+) - b(3)Π → X(1)Σ(+) and (4)(1)Σ(+) → A(1)Σ(+) - b(3)Π laser-induced fluorescence (LIF) spectra were recorded for the natural mixture of the (85)Rb(133)Cs and (87)Rb(133)Cs isotopologues produced in a heat pipe oven. Overall 8730 rovibronic term values of A(1)Σ(+) and b(3)Π states were determined with an uncertainty of 0.01 cm(-1) in the energy range [9012, 14087] cm(-1), covering rotational quantum numbers J ∈ [6, 324]. An energy-based deperturbation analysis performed in the framework of the four A(1)Σ(+) - b(3)Π(Ω = 0, 1, 2) coupled-channels approach reproduces 97% of the experimental term values of both isotopologues with a standard deviation of 0.0036 cm(-1). The reliability of the deperturbed mass-invariant potentials and spin-orbit coupling functions of the interacting A(1)Σ(+) and b(3)Π states is additionally proved by a good reproduction of the A - b → X and (4)(1)Σ(+) → A - b relative intensity distributions. The achieved accuracy of the A - b complex description allowed us to use the latter to assign the observed (5)(1)Σ(+) → A - b and (3)(1)Π → A - b transitions. As is demonstrated, LIF to the A - b complex becomes as informative as to the ground X(1)Σ(+) state, which is confirmed by comparing the results of (4)(1)Σ(+) state analysis based on (4)(1)Σ(+) → A - b LIF with the data from V. Zuters et al. [Phys. Rev. A 87, 022504 (2013)] based on (4)(1)Σ(+) → X LIF. PMID:25399149

  2. Investigation of an unusual low-temperature phase transformation in RbBH{sub 4} by neutron diffraction

    SciTech Connect

    Kitchen, Brian B.; Verdal, Nina; Udovic, Terrence J.; Rush, John J.; Hartman, Michael R.; DeVries, Daniel J.

    2013-07-15

    To investigate the previously reported low-temperature phase transition in rubidium borohydride (RbBH{sub 4}) near 48.5 K, we carried out neutron powder diffraction and vibrational spectroscopy measurements both above and below this temperature on an isotopically-enriched sample of Rb{sup 11}BD{sub 4}. Our diffraction data reflected an average cubic Fm3{sup ¯}m structure with BD{sub 4}{sup −} anion orientational disorder at all temperatures, with no hint of extra Bragg peaks due to long-range orientational order below the transition temperature as reported by others. These structural results and careful analysis of torsional vibrations in RbBD{sub 4} corroborate the results of prior neutron vibrational spectroscopy measurements suggesting that the low-temperature RbBH{sub 4} structure indeed possesses some orientational ordering of the BH{sub 4}{sup −} anions, but of a shorter-ranged nature insensitive to powder diffraction methods. - The neutron powder diffraction pattern of RbBD{sub 4} below the phase transition temperature (shown here in black) is indistinguishable from that collected above the phase transition temperature. The inset depicts the cubic structure that fits the data at both temperatures. - Highlights: • We investigated the nature of the RbBD{sub 4} phase transition using NVS and NPD. • A change in shape of the RbBD{sub 4} torsion mode was observed across the transition. • The RbBD{sub 4} diffraction pattern across this phase transition was unchanged. • The phase transition in RbBD{sub 4} appears to produce only short-range ordering of BD{sub 4}{sup −}.

  3. Pressure-induced phase transition in synthetic trioctahedral Rb-mica

    NASA Astrophysics Data System (ADS)

    Comodi, P.; Drábek, M.; Montagnoli, M.; Rieder, M.; Weiss, Z.; Zanazzi, P. F.

    The crystal structure of a synthetic Rb analog of tetra-ferri-annite (Rb-TFA) 1M with the composition Rb0.99Fe2+3.03(Fe3+ 1.04 Si2.96)O10.0(OH)2.0 was determined by the single-crystal X-ray diffraction method. The structure is homooctahedral (space group C2/m) with M1 and M2 occupied by divalent iron. Its unit cell is larger than that of the common potassium trioctahedral mica, and similar lateral dimensions of the tetrahedral and octahedral sheets allow a small tetrahedral rotation angle α=2.23(6)°. Structure refinements at 0.0001, 1.76, 2.81, 4.75, and 7.2 GPa indicate that in some respects the Rb-TFA behaves like all other micas when pressure increases: the octahedra are more compressible than the tetrahedra and the interlayer is four times more compressible than the 2:1 layer. However, there is a peculiar behavior of the tetrahedral rotation angle α: at lower pressures (0.0001, 1.76, 2.81 GPa), it has positive values that increase with pressure [from 2.23(6)° to 6.3(4)°] as in other micas, but negative values -7.5(5)° and -8.5(9)° appear at higher pressures, 4.75 and 7.2 GPa, respectively. This structural evidence, together with electrostatic energy calculations, shows that Rb-TFA has a Franzini A-type 2:1 layer up to at least 2.81 GPa that at higher pressure yields to a Franzini B-type layer, as shown by the refinements at 4.75 and 7.2 GPa. The inversion of the α angle is interpreted as a consequence of an isosymmetric displacive phase transition from A-type to B-type structure between 2.81 and 4.75 GPa. The compressibility of the Rb-TFA was also investigated by single-crystal X-ray diffraction up to a maximum pressure of 10 GPa. The lattice parameters reveal a sharp discontinuity between 3.36 and 3.84 GPa, which was associated with the phase transition from Franzini-A to Franzini-B structure.

  4. Tet1 is required for Rb phosphorylation during G1/S phase transition

    SciTech Connect

    Huang, Shengsong; Zhu, Ziqi; Wang, Yiqin; Wang, Yanru; Xu, Longxia; Chen, Xuemei; Xu, Qing; Zhang, Qimin; Zhao, Xin; Yu, Yi; Wu, Denglong

    2013-05-03

    Highlights: •Tet1 was required for NIT3T3 proliferation. •Tet1 depletion inhibited G1-S entry. •Cyclin D1 accumulation and Rb phosphorylation was blocked by Tet1 knockdown. -- Abstract: DNA methylation plays an important role in many biological processes, including regulation of gene expression, maintenance of chromatin conformation and genomic stability. TET-family proteins convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), which indicates that these enzymes may participate in DNA demethylation. The function of TET1 has not yet been well characterized in somatic cells. Here, we show that depletion of Tet1 in NIH3T3 cells inhibits cell growth. Furthermore, Tet1 knockdown blocks cyclin D1 accumulation in G1 phase, inhibits Rb phosphorylation and consequently delays entrance to G1/S phase. Taken together, this study demonstrates that Tet1 is required for cell proliferation and that this process is mediated through the Rb pathway.

  5. Pressure-induced phase transitions in multiferroic RbFe(MoO{sub 4}){sub 2}-Raman scattering study

    SciTech Connect

    Maczka, M.; Ptak, M.; Luz-Lima, C.; Freire, P.T.C.; Paraguassu, W.; Guerini, S.; Hanuza, J.

    2011-10-15

    High pressure Raman scattering experiments were performed on RbFe(MoO{sub 4}){sub 2}. These experiments revealed that two phase transitions take place in RbFe(MoO{sub 4}){sub 2} at very low pressures, i.e. between ambient pressure and 0.2 GPa and between 0.4 and 0.7 GPa. Raman results showed that at the first phase transition the room temperature P3-bar m1 phase transforms into the P3-bar phase, which is also observed at ambient pressure below 190 K. The second pressure-induced phase transition occurs into a low symmetry phase of unknown symmetry. The performed lattice dynamics calculations for the P3-bar m1 phase and ab initio calculation of the structural changes under hydrostatic pressure helped us to get better insights into the mechanism of the observed phase transitions. - Graphical abstract: Raman spectra of RbFe(MoO{sub 4}){sub 2} crystal in the high wavenumber region recorded at different pressures during compression experiment. Highlights: > RbFe(MoO{sub 4}){sub 2} exhibits two pressure-induced phase transitions below 0.7 GPa. > First phase transition is from the P3-bar m1 into P3-bar structure. > Phase transitions in RbFe(MoO{sub 4}){sub 2} are similar as in KFe(MoO{sub 4}){sub 2}. > Transitions' pressures are much lower for the rubidium compound.

  6. Preparation of Porous Three-Dimensional Quaternary Thioantimonates(III) ACuSb2 S4 (A = Rb, Cs) through a Surfactant-Thermal Method.

    PubMed

    Shen, Yaying; Liu, Chang; Hou, Peipei; Zhi, Mingjia; Zhou, Chunmei; Chai, Wenxiang; Cheng, Jian-Wen; Liu, Yi; Zhang, Qichun

    2015-12-01

    Two novel porous three-dimensional (3D) quaternary thioantimonates(III) ACuSb2S4 (A = Rb, Cs) were successfully synthesized by employing the neutral surfactant PEG-400 (PEG = polyethyleneglycol) as reaction media, these are significantly different from the known quaternary A-Cu-Sb-S thioantimonates(III) with two-dimensional (2D) crystal structures. This is the first time that crystalline quaternary chalcogenides have been prepared in surfactant media. Both experimental and theoretical studies confirm they are semiconductors with narrow band gaps. Our results demonstrated that the surfactant-thermal strategy could offer a new opportunity to explore novel chalcogenides with diverse crystal structures and interesting physicochemical properties. PMID:26381694

  7. Structure and magnetism in hexagonal tungsten bronze metal oxides AM1/3W8/3O9 (A-K, Rb, Cs; M-Cr, Fe)

    NASA Astrophysics Data System (ADS)

    Ivanov, S. A.; Sahu, J. R.; Voronkova, V. I.; Mathieu, R.; Nordblad, P.

    2015-02-01

    The structure and magnetic properties of hexagonal tungsten bronzes AM1/3W8/3O9 (A-K+, Rb+, Cs+; M- Cr3+, Fe3+) have been investigated. Pure ceramic samples were synthesized by solid-state reaction. The samples have been studied by X-ray powder diffraction in combination with magnetic measurements. The compounds crystallize in hexagonal space group P63/mcm. The substitution of magnetic ions into the WO6 octahedra yields dilute antiferromagnetic Cr3+-O2--Cr3+ (or Fe3+-O2--Fe3+) superexchange interaction causing the appearance of short-range magnetic order at low temperatures. The antiferromagnetic character of the interaction is supported by negative values of the derived Curie-Weiss temperatures, θCW. The magnitude of θCW is found to decrease with increasing ionic radius of the A cation.

  8. Design and Syntheses of Three Novel Carbonate Halides: Cs3 Pb2 (CO3 )3 I, KBa2 (CO3 )2 F, and RbBa2 (CO3 )2 F.

    PubMed

    Liu, Lili; Yang, Yun; Dong, Xiaoyu; Zhang, Bingbing; Wang, Ying; Yang, Zhihua; Pan, Shilie

    2016-02-24

    Three new carbonate halides, Cs3 Pb2 (CO3 )3 I, KBa2 (CO3 )2 F and RbBa2 (CO3 )2 F have been synthesized with hydrothermal and solid-state methods. Cs3 Pb2 (CO3 )3 I is the first product in the lead carbonate iodides family; KBa2 (CO3 )2 F and RbBa2 (CO3 )2 F are the first two centrosymmetric compounds found in the alkaline-alkaline earth carbonate fluorides family. Cs3 Pb2 (CO3 )3 I crystallizes in a centrosymmetric space group C2/m, and exhibits a two- dimensional layered structure which is formed by [Cs4 Pb4 (CO3 )6 I2 ]∞ double-layers consisting of [Pb2 (CO3 )3 I]∞ single-layers bridged by the Cs atoms. KBa2 (CO3 )2 F and RbBa2 (CO3 )2 F, which are isostructural, crystallize in a trigonal crystal system with a centric space group of R3‾ featuring a honeycomb-like framework. First principle calculations indicate that Cs3 Pb2 (CO3 )3 I has a moderate birefringence and explain the difference between the band gaps of the title compounds from electron structures. The effects of cations and halogens on the structures and properties of the title compounds are also discussed. PMID:26822173

  9. Modulation of Framework and Centricity: Cation Size Effect in New Quaternary Selenites, ASc(SeO3)2 (A = Na, K, Rb, and Cs).

    PubMed

    Song, Seung Yoon; Ok, Kang Min

    2015-05-18

    Four new stoichiometrically equivalent quaternary scandium selenites, ASc(SeO3)2 (A = Na, K, Rb, and Cs) have been hydrothermally synthesized using A2CO3, Sc(NO3)3·xH2O (or ScO3), and SeO2 as starting materials. All four materials share similar bond networks that are composed of corner-shared distorted ScO6 octahedra and SeO3 trigonal pyramids. However, each material reveals different frameworks and centricities. Detailed structural analysis suggests that the structural variation is attributed to the difference in size and subsequent coordination number for the alkali metal cations. Powder second-harmonic generation (SHG) measurements on noncentrosymmetric (NCS) RbSc(SeO3)2 show that the compound has an SHG efficiency similar to that of (NH4)H2PO4. The observed SHG efficiency is due to the remaining net polarization after cancellation of oppositely aligned moments for SeO3 and ScO6 groups. Thorough characterizations such as spectroscopic, thermal, and elemental analyses for the new materials are presented as are dipole moment and out-of-center distortion calculations. PMID:25915517

  10. Synthesis and structure of R{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (R = Rb or Cs)

    SciTech Connect

    Serezhkin, V. N.; Peresypkina, E. V.; Grigor’eva, V. A.; Virovets, A. V.; Serezhkina, L. B.

    2015-01-15

    Crystals Rb{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (I) and Cs{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (II) have been synthesized and studied by IR spectroscopy and X-ray diffraction. Crystals I are monoclinic, with the following parameters: a = 12.2118(5) Å, b = 10.2545(3) Å, c = 11.8754(4) Å, β = 110.287(1)°, sp. gr. C2/c, Z = 4, and R = 0.0523. Crystals II are orthorhombic, with a = 13.7309(3) Å, b = 10.5749(2) Å, c = 10.1891(2) Å, sp. gr. Pnma, Z = 4, and R = 0.0411. The basic structural units of crystals I and II are one-core complexes [UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}]{sup 2−}, which belong to the crystallochemical group cis-AB{sub 2}{sup 01}M{sub 2}{sup 1} (A = UO{sub 2}{sup 2+}, B{sup 01} = NO{sub 3}{sup −}, M{sup 1} = NCS{sup −}), which are combined into a framework via electrostatic interactions with ions of alkaline metals R (R = Rb or Cs). The structural features of crystals I and II, which condition the formation of [UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}]{sup 2−} complexes with a cis rather than a trans position of isothiocyanate ions in the coordination sphere of uranyl ions, are discussed.

  11. Incoherence-coherence crossover and low-temperature Fermi-liquid-like behavior in AFe2As2 (A  =  K, Rb, Cs): evidence from electrical transport properties.

    PubMed

    Xiang, Z J; Wang, N Z; Wang, A F; Zhao, D; Sun, Z L; Luo, X G; Wu, T; Chen, X H

    2016-10-26

    We study the normal-state transport properties of AFe2As2 (A  =  K, Rb and Cs) single crystals using Hall coefficient, resistivity and magnetoresistance (MR) measurements. In all three materials, the Hall coefficient R H shows a strong temperature dependence, which is typical for multi-band systems. In particular, R H develops an upturn below a characteristic temperature [Formula: see text], which is in agreement with the incoherence-coherence crossover reported in recent nuclear magnetic resonance studies. A Fermi-liquid-like state, characterized by T (2) behavior of the resistivity and a positive orbital MR obeying Kohler's rule, emerges below T FL  ∼0.4 [Formula: see text]. The superconducting transition temperature T c experiences a simultaneous suppression with [Formula: see text] and T FL as the alkali ion's radius increases from A  =  K to A  =  Cs, suggesting that the unconventional superconductivity in the AFe2As2 series is related to the strength of the electronic coherence. A phase diagram, similar to that in the heavy fermion Kondo lattice system, is obtained. Based on all the experimental evidence, we argue that the physical properties of this family of heavily hole-doped Fe-based superconductors are controlled by the hybridization between itinerant carriers and localized orbitals, and the Kondo scenario could be effective in such a case. PMID:27589485

  12. A low phase noise microwave source for atomic spin squeezing experiments in 87Rb

    NASA Astrophysics Data System (ADS)

    Chen, Zilong; Bohnet, Justin G.; Weiner, Joshua M.; Thompson, James K.

    2012-04-01

    We describe and characterize a simple, low cost, low phase noise microwave source that operates near 6.800 GHz for agile, coherent manipulation of ensembles of 87Rb. Low phase noise is achieved by directly multiplying a low phase noise 100 MHz crystal to 6.8 GHz using a nonlinear transmission line and filtering the output with custom band-pass filters. The fixed frequency signal is single sideband modulated with a direct digital synthesis frequency source to provide the desired phase, amplitude, and frequency control. Before modulation, the source has a single sideband phase noise near -140 dBc/Hz in the range of 10 kHz-1 MHz offset from the carrier frequency and -130 dBc/Hz after modulation. The resulting source is estimated to contribute added spin-noise variance 16 dB below the quantum projection noise level during quantum nondemolition measurements of the clock transition in an ensemble 7 × 105 87Rb atoms.

  13. A low phase noise microwave source for atomic spin squeezing experiments in 87Rb.

    PubMed

    Chen, Zilong; Bohnet, Justin G; Weiner, Joshua M; Thompson, James K

    2012-04-01

    We describe and characterize a simple, low cost, low phase noise microwave source that operates near 6.800 GHz for agile, coherent manipulation of ensembles of (87)Rb. Low phase noise is achieved by directly multiplying a low phase noise 100 MHz crystal to 6.8 GHz using a nonlinear transmission line and filtering the output with custom band-pass filters. The fixed frequency signal is single sideband modulated with a direct digital synthesis frequency source to provide the desired phase, amplitude, and frequency control. Before modulation, the source has a single sideband phase noise near -140 dBc/Hz in the range of 10 kHz-1 MHz offset from the carrier frequency and -130 dBc/Hz after modulation. The resulting source is estimated to contribute added spin-noise variance 16 dB below the quantum projection noise level during quantum nondemolition measurements of the clock transition in an ensemble 7 × 10(5) (87)Rb atoms. PMID:22559559

  14. A low phase noise microwave source for atomic spin squeezing experiments in {sup 87}Rb

    SciTech Connect

    Chen Zilong; Bohnet, Justin G.; Weiner, Joshua M.; Thompson, James K.

    2012-04-15

    We describe and characterize a simple, low cost, low phase noise microwave source that operates near 6.800 GHz for agile, coherent manipulation of ensembles of {sup 87}Rb. Low phase noise is achieved by directly multiplying a low phase noise 100 MHz crystal to 6.8 GHz using a nonlinear transmission line and filtering the output with custom band-pass filters. The fixed frequency signal is single sideband modulated with a direct digital synthesis frequency source to provide the desired phase, amplitude, and frequency control. Before modulation, the source has a single sideband phase noise near -140 dBc/Hz in the range of 10 kHz-1 MHz offset from the carrier frequency and -130 dBc/Hz after modulation. The resulting source is estimated to contribute added spin-noise variance 16 dB below the quantum projection noise level during quantum nondemolition measurements of the clock transition in an ensemble 7 x 10{sup 5} {sup 87}Rb atoms.

  15. Berry phase and its sign in quantum superposition states of thermal 87Rb atoms

    NASA Astrophysics Data System (ADS)

    Welte, S.; Basler, C.; Helm, H.

    2014-02-01

    We investigate the Berry phase in an ensemble of thermal 87Rb atoms which we prepare in a superposition state under conditions near and at electromagnetically induced transparency. The geometric phase is imprinted in the atoms by rotating the laboratory magnetic field. Phase-stabilized light fields permit us to monitor phase changes of the atomic sample in a Ramsey-type interferometer by instant probing of the absorptive response of the atoms as well as by monitoring the free-induction decay of the coherent superposition. The absolute sign of the phase is determined by reference to controllable phase shifts imposed by the experimenter. We prove that the geometric phase is independent of the rotational frequency of the magnetic field in the adiabatic regime, that the phase is additive in multiple rotations, and it is independent of the Landé factor of the atomic magnetic moment, as predicted in Berry's seminal paper. We show that the absolute sign of the phase encodes the sign of the observable angular momentum in relation to laboratory coordinates.

  16. Rb(16)Cd(25.39(3))sb(36): an electron-deficient zintl phase containing infinite dodecahedron chains.

    PubMed

    Zheng, Wu-Zui; Wang, Peng; Wu, Li-Ming; Liu, Yi; Chen, Ling

    2010-07-01

    A novel ternary antimonide Rb(16)Cd(25.39(3))Sb(36) has been synthesized by a solid-state reaction of the appropriate amount of elements in a welded niobium tube at 530 degrees C. The compound crystallizes in orthorhombic space group Cmcm (No. 63) with a = 16.499(5) A, b = 12.391(4) A, c = 12.400(4) A, and Z = 1. The structure features a new 3D network constructed of chains of Rb(+)-centered dodecahedra running along [001]. The atomic distribution of the Cd(8)Sb(12) dodecahedron presents an energetically favored pattern without any Cd-Cd bonding. The formation of the phase and the occurrence of a very narrow phase width of Rb(16)Cd(24+x)Sb(36) [0.94(2) < or = x < or = 1.47(3)] have been studied in detail. The Fermi level of the title compound is expected to be located between those of the hypothetical models of "[Rb(16)Cd(24)Sb(36)](0)" (I, poor metallic) and "[Rb(16)Cd(24)Sb(36)] + 4e" (II, narrow-band-gap semiconductor), which agrees well with the experimental measurements. In the temperature range of 300-473 K, the as-synthesized Rb(16)Cd(25.39(3))Sb(36) exhibits p-type semiconductor behavior and shows temperature-independent thermal conductivities (around 0.49 W/m.K). The electrical conductivity, Seebeck coefficient, and figure of merit (ZT) of Rb(16)Cd(25.39(3))Sb(36) are temperature-dependent; these values are 57.4 S/cm, +81.4 microV/K, and 0.04, respectively, at 466 K. PMID:20509601

  17. Structural modulation of molybdenyl iodate architectures by alkali metal cations in AMoO3(IO3) (A = K, Rb, Cs): a facile route to new polar materials with large SHG responses.

    PubMed

    Sykora, Richard E; Ok, Kang Min; Halasyamani, P Shiv; Albrecht-Schmitt, Thomas E

    2002-03-01

    Three new molybdenyl iodates, KMoO3(IO3) (1), RbMoO3(IO3) (2), and CsMoO3(IO3) (3), have been prepared through the hydrothermal reactions of MoO3 with AIO4 (A = K, Rb, or Cs) at 180 C. These compounds are isolated as nearly colorless, air-stable crystals. Single-crystal X-ray diffraction experiments reveal that 1 possesses a corrugated layered structure constructed from molybdenum oxide chains that are bridged by iodate anions. The puckering of the layers is caused by the alignment of bent molybdenyl (MoO2(2+)) groups along one side of the molybdenum oxide chains. The K+ cations separate these layers from one another and serve to balance charge. In contrast, compounds 2 and 3, which are isostructural, form three-dimensional structures with small cavities filled with Rb+ or Cs+ cations. The differences between the structures of 1 and those of 2 and 3 are due to rotation of the molybdenyl units as translation occurs down the molybdenum oxide chains in order to accommodate the increased size of the Rb+ and Cs+ cations. This rotation allows for the iodate anions to bridge the molybdenum oxide chains in an additional dimension, creating a three-dimensional network structure. Furthermore, while 1 crystallizes in a centrosymmetric space group, 2 and 3 crystallize in polar space groups. Second-harmonic generation measurements on 2 and 3 show large responses of 400x alpha-quartz. Differential scanning calorimetry measurements demonstrate that 2 and 3 are thermally stable to 494 and 486 C, respectively. UV-vis diffuse reflectance spectra of these compounds show a high degree of transparency from 1 to 3 eV and a band gap of 3.1 eV. PMID:11866608

  18. Hyperfine structures of the 2 3 Π(Ω = 1), 2 1 Π(Ω = 1), and 3 3Σ+(Ω = 1) states of ultracold 85 Rb133 Cs via short range photoassociation

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Tae; Shimasaki, Toshihiko; Demille, David

    2016-05-01

    We have observed new short-range photoassociation (PA) to the 2 3 Π(Ω = 1), 2 1 Π(Ω = 1), and 3 3Σ+(Ω = 1) states of ultracold 85 Rb133 Cs molecule, starting with 85 Rb and 133 Cs atoms trapped in their | FRb = 2> and | FCs = 3> hyperfine states in dark SPOT MOTs We have completed vibrational and electronic assignments of those PA states in the perturbed region where assignments were difficult due to strong mixing between electronic states through spin-orbit interaction Further, high-resolution (~10 MHz) PA spectroscopy has revealed rich hyperfine structures in the low J, which we can understand using various coupling schemes (Hund's case bβS or Hund's case bβJ) mainly considering Fermi contact interaction. Similarly, we have also observed PA lines in the strongly perturbed singlet (1 1 Π) and triplet (2 3Σ+) states, which also show similar hyperfine structures. Further, we have observed production of RbCs molecules in the rovibronic ground state through these PA lines via one-photon decay, which opens up the possibility of using these new PA lines as an efficient direct path to the rovibronic ground state.

  19. Phase coexistence in Cs0.8Fe1.6Se2 as seen by x-ray mapping of reciprocal space

    NASA Astrophysics Data System (ADS)

    Bosak, A.; Svitlyk, V.; Krzton-Maziopa, A.; Pomjakushina, E.; Conder, K.; Pomjakushin, V.; Popov, A.; de Sanctis, D.; Chernyshov, D.

    2012-11-01

    AxFe2-ySe2 (A = K, Rb, Cs) superconductors are frequently complex mixtures of phases even in the form usually described as a single crystal. Phases, resulting from phase separation, metrically are very similar, so their detailed characterization is a delicate task, and the existing data are typically scarce. We characterize the room-temperature phase-separated state of Cs0.8Fe1.6Se2 in reciprocal space by means of single-crystal diffraction of synchrotron radiation. Using the arguments of commensurability and detailed analysis of twinning patterns, we augment the previous findings by quantifying the intergrowth state, consisting of the tetragonal phase with ordered Fe vacancies and the minor disordered phase. Compared to the main phase, the minor one is compressed in the tetragonal a-b plane and expanded along the c direction; a set of modulated Bragg rods evidences a planar disorder. Fourfold splitting of the rods and main Bragg peaks implies a rotational twinning; close inspection of the lattice metric indicates that the symmetry of the minor phase is not higher than monoclinic, with a deviation from the orthogonal basis of ˜0.25°.

  20. Phase stability, electronic structure and phonons in CsGeI3

    NASA Astrophysics Data System (ADS)

    Huang, Ling-Yi; Lambrecht, Walter

    Because Ge is smaller than Sn and Pb, CsGeI3 is promising to overcome the stability problems of the perovskite forms of CsSnI3 and CsPbI3 halides toward the denser yellow phase in which octahedra are edge as well as cornersharing in one dimensional chains. This phase has higher gaps and is unsuitable for photovoltaics. CsGeI3 and other trihalide germanates are found to exist in the cubic perovskite phase at high temperature but in a rhombohedral phase in which the Ge is displaced toward three of the halogen neighbors in its surrounding octahedron, accompanied by a rhombohedral distortion of the lattice vectors. We will present density functional total energy calculations and band structures obtained within the quasi-particle self-consistent GW method for both the cubic and rhombohedral phase of CsGeI3. For the latter, we find a gap of 1.6 eV in excellent agreement with recent experiments on its absorption edge. We will also present optical dielectric function and effective mass results for this material and discuss the trends for different types of distortions in halides depending on the chemical composition. The phonons at the Brillouin zone center are calculated and compared to experimental Raman spectra. NSF and DOE.

  1. Structural basis for the phase transitions of Cs2HgCl4.

    PubMed

    Bagautdinov, B; Jobst, A; Ludecke, J; van Smaalen, S

    2001-06-01

    The a(0) x b(0) x 2c(0) twofold superstructure of dicaesium mercury tetrachloride, Cs(2)HgCl(4), at T = 120 K has been determined by single-crystal X-ray diffraction using synchrotron radiation. Lattice parameters were found as a = 9.7105 (2), b = 7.4691 (1), c = 26.8992 (4) A, and beta = 90.368 (1) degrees with the supercell space group P2(1)/c. Refinements on 1828 observed unique reflections converged to R = 0.053 (wR = 0.057) using anisotropic temperature factors for all atoms. This phase is the stable phase of Cs(2)HgCl(4) below 163 K. A quantitative comparison is made of the distortions of the 2c(0) superstructure with the undistorted phase that is stable at room temperature, and with the 3c(0) and 5a(0) superstructures that are stable at temperatures between 163 K and room temperature. The principal difference between the 2c(0) superstructure and all other phases of Cs(2)HgCl(4) is that the Cs cations are displaced away from the centers of their coordination polyhedra in the 2c(0) superstructure. The structural basis for the driving force of the series of phase transitions in this compound is found in the variations of the environments of Cs atoms and in the variations of the distortions of the HgCl(4) tetrahedra. PMID:11373379

  2. Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia.

    PubMed

    Neufeld, Roman; Michel, Reent; Herbst-Irmer, Regine; Schöne, Ralf; Stalke, Dietmar

    2016-08-22

    Alkali metal 1,1,1,3,3,3-hexamethyldisilazide (MHMDSs) are one of the most utilised weakly nucleophilic Brønsted bases in synthetic chemistry and especially in natural product synthesis. Like lithium organics, they aggregate depending on the employed donor solvents. Thus, they show different reactivity and selectivity as a function of their aggregation and solvation state. To date, monomeric LiHMDS with monodentate donor bases was only characterised in solution. Since the first preparation of LiHMDS in 1959 by Wannagat and Niederprüm, all efforts to crystallise monomeric LiHMDS in the absence of chelating ligands failed. Herein, we present ammonia adducts of LiHMDS, NaHMDS, KHMDS, RbHMDS and CsHMDS with unprecedented aggregation motifs: 1) The hitherto missing monomeric key compound in the LiHMDS aggregation architectures. Monomeric crystal structures of trisolvated LiHMDS (1) and NaHMDS (2), showing unique intermolecular hydrogen bonds, 2) the unprecedented tetrasolvated KHMDS (3) and RbHMDS (4) dimers and 3) the disolvated CsHMDS (5) dimer with very close intermolecular Si-CH3 ⋅⋅⋅Cs s-block "agostic" interactions have been prepared and characterised by single-crystal X-ray structure analysis. PMID:27457218

  3. Syntheses and crystal structures of two novel alkaline uranyl chromates A{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2} (A=Rb, Cs) with bidentate coordination mode of uranyl ions by chromate anions

    SciTech Connect

    Siidra, Oleg I.

    2012-03-15

    Single crystals of Cs{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2} and Rb{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2} were prepared by solid state reactions. The structures are based upon the [(UO{sub 2})(CrO{sub 4}){sub 2}]{sup 2-} chains. Within the chains, UrO{sub 5} pentagonal bipyramids (Ur=uranyl) form Ur{sub 2}O{sub 8} dimers, which are linked via CrO{sub 4} tetrahedra into one-dimensional chains. The CrO{sub 4} tetrahedra coordinate uranyl ions in both mono- and bidentate fashion, which is unusual for uranyl chromates. The bidentate coordination has a strong influence upon geometrical parameters of both U and Cr coordination polyhedra. The conformation of the chains in 1 and 2 is different due to the different size of the Cs{sup +} and Rb{sup +} cations. - Graphical abstract: Uranyl chromate chain with monodentate and bidentate coordination mode of uranyl cations by CrO{sub 4} tetrahedra in Cs{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2}. Highlights: Black-Right-Pointing-Pointer Single crystals of novel uranyl chromates were prepared by solid state reactions. Black-Right-Pointing-Pointer The CrO{sub 4} tetrahedra coordinate uranyl ions in both mono- and bidentate fashion. Black-Right-Pointing-Pointer The bidentate coordination has a strong influence upon geometrical parameters.

  4. Phase dependence of secondary electron emission at the Cs-Sb-Si (111) interface

    NASA Astrophysics Data System (ADS)

    Govind, Govind; Kumar, Praveen; Shivaprasad, S. M.

    2009-06-01

    The multi-alkali antimonides adsorption on Si (111) surface has drawn much attention of several surface science studies due to its importance in both, fundamental and technological aspects of night vision devices & photocathodes. We report the formation of alkali metal antimonide ternary interface on Si(111)- 7×7 surface and in-situ characterization by X-ray Photoelectron Spectroscopy (XPS). The results show that Cs adsorption on clean Si(111) surface follows the layer-by-layer (Frank van der Merwe) growth mode at low flux rate, while Sb grows as islands (Volmer-Weber) on Cs/Si surface. The changes in the Si (2p) and Cs (3d) core level spectra show the formation of a ternary interface (Sb/Cs/Si) at room temperature, which is further confirmed by changes in the density of states in the valence band spectra. The temperature controlled desorption of ternary interface, by monitoring the chemical species remnant on the surface after annealing at different temperatures, reveal that the Sb islands desorb at <550° C while Cs monolayer desorbs at temperatures >750° C, which implies a stronger Cs-Si bond to Cs-Sb bond. The work function changes from 3.9 eV to 0.8 eV for Cs adsorption on Si, which further reduces to 0.65 eV after Sb adsorption on the Cs/Si interface. The changes in work function corresponds to the compositional and chemical nature of the interface and thus indicate that the secondary electron emission is an extremely phase dependent phenomena.

  5. Syntheses and characterization of one-dimensional alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs)

    SciTech Connect

    Yohannan, Jinu P.; Vidyasagar, Kanamaluru

    2015-01-15

    Three new isostructural quaternary antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs) have been synthesized by using alkali metal thiosulfate flux and structurally characterized by X-ray diffraction. Their structures contain A{sup +} ions around the [Sb{sub 2}Sn{sub 3}S{sub 10}]{sup 2−} chains, which are built from SbS{sub 3} pyramids, SnS{sub 6} octahedra and SnS{sub 4} tetrahedra. Raman and Mössbauer spectroscopic measurements corroborate the oxidation states and coordination environments of Sb(III) and Sn(IV). All three compounds are wide band gap semiconductors. Potassium compound undergoes partial exchange with strontium, cadmium and lead ions. - Graphical abstract: Syntheses, crystal structure, spectroscopic and partial ion-exchange studies of new one-dimensional alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs) are described. - Highlights: • Syntheses of new alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs). • Wide band gap semiconductors with one-dimensional structure. • Topotactic partial exchange of K{sup +} ions of K{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} with Sr{sup 2+}, Cd{sup 2+} and Pb{sup 2+} ions.

  6. Spectroscopic data, spin-orbit functions, and revised analysis of strong perturbative interactions for the A {sup 1{Sigma}+} and b {sup 3{Pi}} states of RbCs

    SciTech Connect

    Docenko, O.; Tamanis, M.; Ferber, R.; Bergeman, T.; Kotochigova, S.; Stolyarov, A. V.

    2010-04-15

    The current interest in producing ultracold RbCs molecules by optical excitation from weakly bound Feshbach resonances and stimulated decay to the absolute ground state requires detailed analyses of the intermediate excited states. In this study, we present two sets of experimental Fourier-transform spectroscopic data of the A {sup 1{Sigma}+}-b {sup 3{Pi}} complex. The A-b mixed vibrational levels are the most likely candidates to be intermediates in the molecular formation. The more recent and more accurate data set is from mixed A-b{yields}X transitions, while the second is derived in large part from (4) {sup 1{Sigma}+{yields}}A-b emission and extends to higher A-b energy levels. From a detailed analysis of the spectroscopic data we obtain term values which allow one to construct potentials and spin-orbit functions. Vibrational numbering of the A state has been raised by one quantum over a previous report [T. Bergeman et al., Phys. Rev. A 67, 050501 (2003)] while the numbering of the b state is established with a considerable degree of certainty with help of data on the {sup 85}Rb{sup 133}Cs and {sup 87}Rb{sup 133}Cs isotopomers. In addition, we have performed calculations of spin-orbit functions by two distinct methods. The fitted spin-orbit coupling matrix element between the two {Omega}{sup p}=0{sup +} states, A {sup 1{Sigma}+} and b {sup 3{Pi}}{sub 0+}, happens to agree rather well with the results from both of these methods, while for the diagonal b {sup 3{Pi}} state spin-orbit function, the fitted function agrees fairly well with that obtained by the other method.

  7. Decays of the Three Top Contributors to the Reactor ν[over ¯]_{e} High-Energy Spectrum, ^{92}Rb, ^{96gs}Y, and ^{142}Cs, Studied with Total Absorption Spectroscopy.

    PubMed

    Rasco, B C; Wolińska-Cichocka, M; Fijałkowska, A; Rykaczewski, K P; Karny, M; Grzywacz, R K; Goetz, K C; Gross, C J; Stracener, D W; Zganjar, E F; Batchelder, J C; Blackmon, J C; Brewer, N T; Go, S; Heffron, B; King, T; Matta, J T; Miernik, K; Nesaraja, C D; Paulauskas, S V; Rajabali, M M; Wang, E H; Winger, J A; Xiao, Y; Zachary, C J

    2016-08-26

    We report total absorption spectroscopy measurements of ^{92}Rb, ^{96gs}Y, and ^{142}Cs β decays, which are the most important contributors to the high energy ν[over ¯]_{e} spectral shape in nuclear reactors. These three β decays contribute 43% of the ν[over ¯]_{e} flux near 5.5 MeV emitted by nuclear reactors. This ν[over ¯]_{e} energy is particularly interesting due to spectral features recently observed in several experiments including the Daya Bay, Double Chooz, and RENO Collaborations. Measurements were conducted at Oak Ridge National Laboratory by means of proton-induced fission of ^{238}U with on-line mass separation of fission fragments and the Modular Total Absorption Spectrometer. We observe a β-decay pattern that is similar to recent measurements of ^{92}Rb, with a ground-state to ground-state β feeding of 91(3)%. We verify the ^{96gs}Y ground-state to ground-state β feeding of 95.5(20)%. Our measurements substantially modify the β-decay feedings of ^{142}Cs, reducing the β feeding to ^{142}Ba states below 2 MeV by 32% when compared with the latest evaluations. Our results increase the discrepancy between the observed and the expected reactor ν[over ¯]_{e} flux between 5 and 7 MeV, the maximum excess increases from ∼10% to ∼12%. PMID:27610847

  8. The determination of potential energy curve and dipole moment of the (5)0{sup +} electronic state of {sup 85}Rb{sup 133}Cs molecule by high resolution photoassociation spectroscopy

    SciTech Connect

    Yuan, Jinpeng; Zhao, Yanting Ji, Zhonghua; Li, Zhonghao; Xiao, Liantuan; Jia, Suotang; Kim, Jin-Tae

    2015-12-14

    We present the formation of ultracold {sup 85}Rb{sup 133}Cs molecules in the (5)0{sup +} electronic state by photoassociation and their detection via resonance-enhanced two-photon ionization. Up to v = 47 vibrational levels including the lowest v = 0 vibrational and lowest J = 0 levels are identified with rotationally resolved high resolution photoassociation spectra. Precise Dunham coefficients are determined for the (5)0{sup +} state with high accuracy, then the Rydberg-Klein-Rees potential energy curve is derived. The electric dipole moments with respect to the vibrational numbers of the (5)0{sup +} electronic state of {sup 85}Rb{sup 133}Cs molecule are also measured in the range between 1.9 and 4.8 D. These comprehensive studies on previously unobserved rovibrational levels of the (5)0{sup +} state are helpful to understand the molecular structure and discover suitable transition pathways for transferring ultracold atoms to deeply bound rovibrational levels of the electronic ground state.

  9. A multinuclear solid-state NMR study of alkali metal ions in tetraphenylborate salts, M[BPh4] (M = Na, K, Rb and Cs): what is the NMR signature of cation-pi interactions?

    PubMed

    Wu, Gang; Terskikh, Victor

    2008-10-16

    We report a multinuclear solid-state ( (23)Na, (39)K, (87)Rb, (133)Cs) NMR study of tetraphenylborate salts, M[BPh 4] (M = Na, K, Rb, Cs). These compounds are isostructural in the solid state with the alkali metal ion surrounded by four phenyl groups resulting in strong cation-pi interactions. From analyses of solid-state NMR spectra obtained under stationary and magic-angle spinning (MAS) conditions at 11.75 and 21.15 T, we have obtained the quadrupole coupling constants, C Q, and the chemical shift tensor parameters for the alkali metal ions in these compounds. We found that the observed quadrupole coupling constant for M (+) in M[BPh 4] is determined by a combination of nuclear quadrupole moment, Sternheimer antishielding factor, and unit cell dimensions. On the basis of a comparison between computed paramagnetic and diamagnetic contributions to the total chemical shielding values for commonly found cation-ligand interactions, we conclude that cation-pi interactions give rise to significantly lower paramagnetic shielding contributions than other cation-ligand interactions. As a result, highly negative chemical shifts are expected to be the NMR signature for cations interacting exclusively with pi systems. PMID:18816043

  10. Low temperature phase transition and crystal structure of CsMgPO{sub 4}

    SciTech Connect

    Orlova, Maria; Khainakov, Sergey; Michailov, Dmitriy; Perfler, Lukas; Langes, Christoph; Kahlenberg, Volker; Orlova, Albina

    2015-01-15

    CsMgPO{sub 4} doped with radioisotopes is a promising compound for usage as a radioactive medical source. However, a low temperature phase transition at temperatures close to ambient conditions (∼−40 °C) was observed. Information about such kind of structural changes is important in order to understand whether it can cause any problem for medical use of this compound. The phase transition has been investigated in detail using synchrotron powder diffraction, Raman spectroscopy and DFT calculations. The structure undergoes a transformation from an orthorhombic modification, space group Pnma (RT phase) to a monoclinic polymorph, space group P2{sub 1}/n (LT phase). New LT modification adopts similar to RT but slightly distorted unit cell: a=9.58199(2) Å, b=8.95501(1) Å, c=5.50344(2) Å, β=90.68583(1)°, V=472.198(3) Å{sup 3}. CsMgPO{sub 4} belongs to the group of framework compounds and is made up of strictly alternating MgO{sub 4}- and PO{sub 4}-tetrahedra sharing vertices. The cesium counter cations are located in the resulting channel-like cavities. Upon the transformation a combined tilting of the tetrahedra is observed. A comparison with other phase transitions in ABW-type framework compounds is given. - Graphical abstract: Structural behavior of β-tridymite-type phosphate CsMgPO{sub 4}, considered as potential chemical form for radioactive Cs-source has been studied at near ambient temperatures. A phase transition at (∼−40 °C) has been found and investigated. It has been established that the known orthorhombic RT modification, space group Pnma, adopts a monoclinic cell with space group P2{sub 1}/n at low temperatures. In this paper, we present results of structural analysis of changes accompanying this phase transition and discuss its possible impact on the application properties. - Highlights: • β-Tridymite type phosphate CsMgPO{sub 4} undergoes so called translationengleiche phase transition of index 2 at −40 °C. • The structure

  11. High temperature redox reactions with uranium: Synthesis and characterization of Cs(UO{sub 2})Cl(SeO{sub 3}), Rb{sub 2}(UO{sub 2}){sub 3}O{sub 2}(SeO{sub 3}){sub 2}, and RbNa{sub 5}U{sub 2}(SO{sub 4}){sub 7}

    SciTech Connect

    Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

    2013-10-15

    Cs(UO{sub 2})Cl(SeO{sub 3}) (1), Rb{sub 2}(UO{sub 2}){sub 3}O{sub 2}(SeO{sub 3}){sub 3} (2), and RbNa{sub 5}U{sub 2}(SO{sub 4}){sub 7} (3) single crystals were synthesized using CsCl, RbCl, and a CuCl/NaCl eutectic mixture as fluxes, respectively. Their lattice parameters and space groups are as follows: P2{sub 1}/n (a=6.548(1) Å, b=11.052(2) Å, c=10.666(2) Å and β=93.897(3)°), P1{sup ¯} (a=7.051(2) Å, b=7.198(2) Å, c=8.314(2) Å, α=107.897(3)°, β=102.687(3)° and γ=100.564(3)°) and C2/c (a=17.862(4) Å, b=6.931(1) Å, c=20.133(4) Å and β=109.737(6)°. The small anionic building units found in these compounds are SeO{sub 3}{sup 2−} and SO{sub 4}{sup 2−} tetrahedra, oxide, and chloride. The crystal structure of the first compound is composed of [(UO{sub 2}){sub 2}Cl{sub 2}(SeO{sub 3}){sub 2}]{sup 2−} chains separated by Cs{sup +} cations. The structure of (2) is constructed from [(UO{sub 2}){sub 3}O{sub 11}]{sup 16−} chains further connected through selenite units into layers stacked perpendicularly to the [0 1 0] direction, with Rb{sup +} cations intercalating between them. The structure of compound (3) is made of uranyl sulfate layers formed by edge and vertex connections between dimeric [U{sub 2}O{sub 16}] and [SO{sub 4}] polyhedra. These layers contain unusual sulfate–metal connectivity as well as large voids. - Graphical abstract: A new family of uranyl selenites and sulfates has been prepared by high-temperature redox reactions. This compounds display new bonding motifs. Display Omitted - Highlights: • Low-dimensional Uranyl Oxoanion compounds. • Conversion of U(IV) to U(VI) at high temperatures. • Dimensional reduction by both halides and stereochemically active lone-pairs.

  12. A Phase Ia Study to Assess the Safety and Immunogenicity of New Malaria Vaccine Candidates ChAd63 CS Administered Alone and with MVA CS

    PubMed Central

    de Barra, Eoghan; Hodgson, Susanne H.; Ewer, Katie J.; Bliss, Carly M.; Hennigan, Kerrie; Collins, Ann; Berrie, Eleanor; Lawrie, Alison M.; Gilbert, Sarah C.; Nicosia, Alfredo

    2014-01-01

    Background Plasmodium falciparum (P. falciparum) malaria remains a significant cause of mortality and morbidity throughout the world. Development of an effective vaccine would be a key intervention to reduce the considerable social and economic impact of malaria. Methodology We conducted a Phase Ia, non-randomized, clinical trial in 24 healthy, malaria-naïve adults of the chimpanzee adenovirus 63 (ChAd63) and modified vaccinia virus Ankara (MVA) replication-deficient viral vectored vaccines encoding the circumsporozoite protein (CS) of P. falciparum. Results ChAd63-MVA CS administered in a heterologous prime-boost regime was shown to be safe and immunogenic, inducing high-level T cell responses to CS. With a priming ChAd63 CS dose of 5×109 vp responses peaked at a mean of 1947 SFC/million PBMC (median 1524) measured by ELIspot 7 days after the MVA boost and showed a mixed CD4+/CD8+ phenotype. With a higher priming dose of ChAd63 CS dose 5×1010 vp T cell responses did not increase (mean 1659 SFC/million PBMC, median 1049). Serum IgG responses to CS were modest and peaked at day 14 post ChAd63 CS (median antibody concentration for all groups at day 14 of 1.3 µg/ml (range 0–11.9), but persisted throughout late follow-up (day 140 median antibody concentration groups 1B & 2B 0.9 µg/ml (range 0–4.7). Conclusions ChAd63-MVA is a safe and highly immunogenic delivery platform for the CS antigen in humans which warrants efficacy testing. Trial Registration ClinicalTrials.gov NCT01450280 PMID:25522180

  13. Disruption of RB/E2F-1 interaction by single point mutations in E2F-1 enhances S-phase entry and apoptosis.

    PubMed Central

    Shan, B; Durfee, T; Lee, W H

    1996-01-01

    The retinoblastoma protein (RB) has been proposed to function as a negative regulator of cell proliferation by complexing with cellular proteins such as the transcription factor E2F. To study the biological consequences of the RB/E2F-1 interaction, point mutants of E2F-1 which fail to bind to RB were isolated by using the yeast two-hybrid system. Sequence analysis revealed that within the minimal 18-amino acid peptide of E2F-1 required for RB binding, five residues, Tyr (position 411), Glu (419), and Asp-Leu-Phe (423-425), are critical. These amino acids are conserved among the known E2F family members. While mutation of any of these five amino acids abolished binding to RB, all mutants retained their full transactivation potential. Expression of mutated E2F-1, when compared with that of wild-type, significantly accelerated entry into S phase and subsequent apoptosis. These results provide direct genetic evidence for the biological significance of the RB/E2F interaction and strongly suggest that the interplay between RB and E2F is critical for proper cell cycle progression. Images Fig. 3 Fig. 4 PMID:8570615

  14. Binding energies of the ground triplet state a{sup 3}Σ{sub u}{sup +} of Rb{sub 2} and Cs{sub 2} in terms of the generalized Le Roy–Bernstein near-dissociation expansion

    SciTech Connect

    Sovkov, V. B.; Ivanov, V. S.

    2014-04-07

    Formulae of Le Roy–Bernstein near-dissociation theory are derived in a general isotope–invariant form, applicable to any term in the rotational expansion of a diatomic ro-vibrational term value. It is proposed to use the generalized Le Roy–Bernstein expansion to describe the binding energies (ro-vibrational term values) of the ground triplet state a{sup 3}Σ{sub u}{sup +} of alkali metal dimers. The parameters of this description are determined for Rb{sub 2} and Cs{sub 2} molecules. This approach gives a recipe to calculate the whole variety of the binding energies with characteristic accuracies from ∼1 × 10{sup −3} to 1 × 10{sup −2} cm{sup −1} using a relatively simple algebraic equation.

  15. Structural Investigation of a New Series of Long-Chain Polyphosphates. Crystal Structure of AgK(PO 3) 2 and Crystal Data for Ag M(PO 3) 2 with M = K, Rb, Cs, and TI

    NASA Astrophysics Data System (ADS)

    Averbuch-Pouchot, M. T.

    1993-01-01

    Single crystals of four isotypic AgM(PO3)2 compounds (M = K, Rb, Cs, and TI) have been prepared by flux methods. Crystal structure determination, performed with the silver-potassium salt, shows these four compounds are long-chain polyphosphates. AgK(PO3)2 is monoclinic, P21/a, with Z = 4 and the following unit cell dimensions: a = 7.490(6), b = 13.175(10), c = 6.037(5) Å, β = 94.32(6)°. The final R value is 0.031 for 1887 independent reflections. Infinite (PO3)n chains are directed along the a direction with a period of four tetrahedra, while associated cations form very corrugated layers waving between the phosphoric chains.

  16. Synthesis and characterization of new fluoride-containing manganese vanadates A2Mn2V2O7F2 (A=Rb, Cs) and Mn2VO4F

    NASA Astrophysics Data System (ADS)

    Sanjeewa, Liurukara D.; McGuire, Michael A.; Smith Pellizzeri, Tiffany M.; McMillen, Colin D.; Ovidiu Garlea, V.; Willett, Daniel; Chumanov, George; Kolis, Joseph W.

    2016-09-01

    Large single crystals of A2Mn2V2O7F2 (A=Rb, Cs) and Mn2VO4F were grown using a high-temperature (~600 °C) hydrothermal technique. Single crystal X-ray diffraction and powder X-ray diffraction were utilized to characterize the structures, which both possess MnO4F2 building blocks. The A2Mn2V2O7F2 series crystallizes as a new structure type in space group Pbcn (No. 60), Z=4 (Rb2Mn2V2O7F2: a=7.4389(17) Å, b=11.574(3) Å, c=10.914(2) Å; Cs2Mn2V2O7F2: a=7.5615(15) Å, b=11.745(2) Å, c=11.127(2) Å). The structure is composed of zigzag chains of edge-sharing MnO4F2 units running along the a-axis, and interconnected through V2O7 pyrovanadate groups. Temperature dependent magnetic susceptibility measurements on this interesting one-dimensional structural feature based on Mn2+ indicated that Cs2Mn2V2O7F2 is antiferromagnetic with a Neél temperature, TN=~3 K and a Weiss constant, θ, of -11.7(1) K. Raman and infrared spectra were also analyzed to identify the fundamental V-O vibrational modes in Cs2Mn2V2O7F2. Mn2(VO4)F crystalizes in the monoclinic space group of C2/c (no. 15), Z=8 with unit cell parameters of a=13.559(2) Å, b=6.8036(7) Å, c=10.1408(13) Å and β=116.16(3)°. The structure is associated with those of triplite and wagnerite. Dynamic fluorine disorder gives rise to complex alternating chains of five-and six-coordinate Mn2+. These interpenetrating chains are additionally connected through isolated VO4 tetrahedra to form the condensed structure.

  17. Charge transport in charge-ordered layered crystals θ-(BEDT-TTF)2MZn(SCN)4 (M=Cs,Rb) : Effects of long-range Coulomb interaction and the Pauli exclusion principle

    NASA Astrophysics Data System (ADS)

    Takahide, Yamaguchi; Kimata, Motoi; Hazama, Kaori; Terashima, Taichi; Uji, Shinya; Konoike, Takako; Yamamoto, Hiroshi M.

    2010-06-01

    We have measured the current-voltage (I-V) characteristics, dielectric properties, and magnetoresistances of insulating layered organic crystals θ-(BEDT-TTF)2MZn(SCN)4 (M=Cs,Rb) , in which electron-electron Coulomb interactions are considered to induce charge ordering. The in-plane I-V characteristics follow the power law with a large exponent that exceeds 10 in the low-temperature limit. The nonlinear I-V characteristics are attributed to electric field induced unbinding of pairs of an electron and a hole that are thermally excited and attracted to each other due to two-dimensional long-range Coulomb interaction. The temperature and frequency dependences of the in-plane dielectric constant for M=Cs are explained by the polarization of the electron-hole bound pairs, consistently with the I-V characteristics. The large dielectric anisotropy ( ≈100 at 0.6 K) observed for M=Cs suggests two-dimensional long-range Coulomb interaction, which is also consistent with the explanation of the nonlinear I-V curves. The organic crystals have a large positive magnetoresistance ratio, e.g., ≈10000% for M=Cs in a magnetic field of 10 T at 0.1 K. The magnetoresistance is nearly independent of the magnetic field orientation despite the highly two-dimensional charge transport, indicating that it is electron-spin related. The magnetoresistance may be caused by magnetic field induced parallel alignment of spins of mobile and localized electrons, both in the highest occupied molecular orbital of a BEDT-TTF molecule, and by the resulting suppression of conduction due to the Pauli exclusion principle.

  18. Distributions of Li+, Na+ K+, Rb+, and Cs+ tracer ions in erythrocytes at 38 degrees C in relation to entry rates of these ions into cells at 0 degree C.

    PubMed

    Salminen, S; Ekman, A; Rastas, J

    2000-01-01

    Forces that are able to transport Na+ and K+ into two compartments were investigated. A modified Nernst-Planck equation for coupled flows of electric current, water, and ions was integrated. The result shows that if alkali ions in the ion channel of the cell membrane are separated by their electric-current-induced inward flows against an electro-osmotic outward flow of water, the logarithms of the stationary cell/medium distributions of these ions should be proportional to the inverse of their diffusion mobilities. The relationship was tested in human erythrocytes. From inward and outward movements of tracer alkali ions, calculations were made to obtain their stationary distributions at infinite time. The cell/medium distributions determined in this way at 38 degrees C are Li+ = 0.59, 22Na+ = 0.044, 42K+ = 10.0, 86Rb+ = 11.9, and 137Cs+ = 3.07. The entry rates of ions into the cell at 0 degrees C are understood to represent their diffusion mobilities in the pump channel. The entry rates are Li+ = 1.44, 2Na+ = 1, 42K+ = 2.22, 86Rb+ = 2.39, and 137Cs+ = 1.72 relative to that of 22Na+. There is an expected negative correlation between the logarithms of the stationary cell/ medium distributions at 38 degrees C and the inverse of the entry rates into the cell at 0 degrees C for the five ions. It is suggested that the proposed physical forces cause the separation of alkali ions in the channel of Na,K-ATPase. PMID:11156287

  19. On the pressure induced phase of Na{sub 2}CsC{sub 60}

    SciTech Connect

    Morosin, B.; Schirber, J.E.; Jorgensen, J.D.; Kwei, G.H.; Yildirim, T. |; Fischer, J.E.

    1996-06-01

    Neutron powder diffraction at pressures to 6 kbar in gaseous Ne has been used to study the pressure-induced phase transition and compressibilities of Na{sub 2}CsC{sub 60}. The pressure-induced phase can be achieved by compression to about 5 kbar at room temperature. If cooled, this phase can be retained below 200 K upon release of the pressure. The structure is orthorhombic as previously reported (but may differ in its detailed crystal structure) with lattice constants near 80 K and ambient pressure of a=9.385 A, b=10.06 A, and c=14.36 A. Corresponding linear compressibilities are 0.0004, 0014, and 0.0017 kbar{sup -1}, respectively. Identical pressure temperature cycling results in a superconductor with an unexpectedly low pressure dependence for {Tc} while in this phase. Models for the superconducting behavior of this compound are discussed.

  20. Phase stability and transformations in the halide perovskite CsSnI3

    NASA Astrophysics Data System (ADS)

    da Silva, E. Lora; Skelton, Jonathan M.; Parker, Stephen C.; Walsh, Aron

    2015-04-01

    We employ the quasiharmonic approximation to study the temperature-dependent lattice dynamics of the four different phases of cesium tin iodide (CsSnI3). Within this framework, we obtain the temperature dependence of a number of structural properties, including the cell volume, bulk modulus, and Grüneisen parameter. The Gibbs free energy of each phase is compared against the temperature-dependent Helmholtz energy obtained from the equilibrium structure within the harmonic approximation. We find that the black tetragonal perovskite phase is not dynamically stable up to at least 500 K, with the phonon dispersion displaying negative optic modes, which pass through all of the high-symmetry wave vectors in the Brillouin zone. The main contributions to the negative modes are found to be motions of the Cs atom inside the perovskite cage. The black cubic perovskite structure shows a zone-boundary instability, indicated by soft modes at the special q points M and R . These modes are present in calculations at the equilibrium (0 K) lattice constant, while at finite temperature additional negative modes develop at the zone center, indicating a ferroelectric instability. The yellow crystal, composed of one-dimensional (SnI6)n double chains, has the same heat of formation as the orthorhombic perovskite phase at 0 K, but becomes less energetically favorable at higher temperatures, due to its higher free energy.

  1. Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

    NASA Astrophysics Data System (ADS)

    Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

    2015-07-01

    MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including X-ray diffraction, electron backscatter diffraction, energy dispersive X-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

  2. Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

    SciTech Connect

    Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

    2015-05-16

    MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including x-ray diffraction, electron backscatter diffraction, energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

  3. Crystal structure and phase transition mechanisms in CsFe{sub 2}F{sub 6}

    SciTech Connect

    Molokeev, M.S.; Bogdanov, E.V.; Misyul, S.V.; Tressaud, A.; Flerov, I.N.

    2013-04-15

    For the first time, structural phase transitions induced by the temperature were found in A{sub x}M{sub x}{sup II}M{sub (1−x)}{sup III}F{sub 3} fluorides with the defect pyrochlore structure (Fd3{sup ¯}m, Z=8). The room temperature structure of CsFe{sub 2}F{sub 6} was determined using X-ray powder diffraction technique. This phase was found to be ordered with the Pnma space group. The study of the temperature stability of orthorhombic structure by differential scanning calorimeter between 100 K and 700 K has shown a succession of phase transitions. The Pnma (Z=4)→Imma (Z=4)→I4{sub 1}/amd (Z=4)→Fd3{sup ¯}m (Z=8) structural sequence was proposed to occur within a rather narrow temperature range 500–560 K. The mechanism of structural transition has been mainly associated with the rotation of (MF{sub 6}) octahedra and small displacements of some Fe atoms. This assumption is in good agreement with the low experimental entropy value, which is characteristic for displacive transformations. - Graphical abstract: Mechanism of phase transition between the HT cubic form of CsFe{sub 2}F{sub 6} at 573 K (left) and the room temperature orthorhombic form at 298 K (right). The grey rectangles are clusters of five FeF{sub 6} octahedra. Highlights: ► Structural transition found for the first time in CsFe{sub 2}F{sub 6} with defect pyrochlore type. ► Fe{sup II} and Fe{sup III} atoms are ordered in room temperature Pnma form of CsFe{sub 2}F{sub 6}. ► Pnma(Z=4)→Imma(Z=4)→I4{sub 1}/amd(Z=4)→Fd-3m(Z=8) transition sequence is proposed. ► Structural transition due to rotation of MF{sub 6} groups+small displacements of Fe atoms. ► The low value of the entropy is in agreement with a displacive-type transition.

  4. Ferroelastic phase transition in Cs3Bi2I9: A neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Jorio, A.; Currat, R.; Myles, D. A. A.; McIntyre, G. J.; Aleksandrova, I. P.; Kiat, J. M.; Saint-Grégoire, P.

    2000-02-01

    Crystalline Cs3Bi2I9, with the P63/mmc symmetry at room temperature was studied by Laue and four-circle neutron diffractometry from room temperature down to 50 K. At T0=220 K the crystal undergoes a second-order proper ferroelastic phase transition to a polydomain structure with a nonprimitive monoclinic C12/m1 space group. Satellites were not found below T0, indicating that the continuous distribution of sites observed in previous 127I nuclear quadrupole resonance experiments is due either to an undetected incommensurate phase characterized by a very small displacement amplitude, or due to the fraction of the crystal volume occupied by domain walls. We argue that thick domain walls are expected in the present structure due to the absence of mechanical compatibility between domains.

  5. Ion mobility, conductivity, structure, and phase transitions in K0.7M0.3SbF4 compounds with M=Rb, NH4

    NASA Astrophysics Data System (ADS)

    Kavun, V. Ya.; Gerasimenko, A. V.; Uvarov, N. F.; Polyantsev, M. M.; Zemnukhova, L. A.

    2016-09-01

    Ion mobility, phase transitions, structure, and conductivity in the K0.7M0.3SbF4 (M=Rb, NH4) compounds were studied by NMR spectroscopy, DSC, X-ray, and conductivity measurements. The predominant form in the ion motions resulting from the phase transition of high modification was diffusion of fluoride and ammonium ions above 450 K. The high-temperature phases of K0.7M0.3SbF4 (M=Rb, NH4) are superionic, while their conductivity attains the values of ~10-2-10-4 S/cm at 450-500 K. The structures of α- and β-modifications of the K0.7Rb0.3SbF4 are monoclinic (space group P21/m). The main structural units in them are statistically substituting each other K+ and Rb+ cations and complex ∞1[ SbF4]- anions linked into zigzag-like chains by bridge fluorine atoms. The nearest surrounding of each antimony atom contains five fluorine atoms, so that the antimony coordination polyhedron can be described, taking into account the lone electron pair, as a distorted SbF5E octahedron (ψ-octahedron).

  6. Effects of thermal and quantum fluctuations on the phase diagram of a spin-1 {sup 87}Rb Bose-Einstein condensate

    SciTech Connect

    Phuc, Nguyen Thanh; Kawaguchi, Yuki; Ueda, Masahito

    2011-10-15

    We investigate the effects of thermal and quantum fluctuations on the phase diagram of a spin-1 {sup 87}Rb Bose-Einstein condensate (BEC) under the quadratic Zeeman effect. Due to the large ratio of spin-independent to spin-dependent interactions of {sup 87}Rb atoms, the effect of noncondensed atoms on the condensate is much more significant than that in scalar BECs. We find that the condensate and spontaneous magnetization emerge at different temperatures when the ground state is in the broken-axisymmetry phase. In this phase, a magnetized condensate induces spin coherence of noncondensed atoms in different magnetic sublevels, resulting in temperature-dependent magnetization of the noncondensate. We also examine the effect of quantum fluctuations on the order parameter at absolute zero and find that the ground-state phase diagram is significantly altered by quantum depletion.

  7. Crystal Structure and Ionic Conductivity of Three Polymorphic Phases of Rubidium Trefluoromethyl Sulfonate, RbSO3CF3

    SciTech Connect

    Hildebrandt,L.; Dinnebier, R.; Jansen, M.

    2006-01-01

    The crystal structures of three polymorphic phases of rubidium trifluoromethyl sulfonate (RbSO{sub 3}CF{sub 3}, rubidium 'triflate') were solved from X-ray powder diffraction data. At room temperature, rubidium triflate crystallizes in the monoclinic space group Cm with lattice parameters of a = 19.9611(5) Angstroms, b = 23.4913(7) Angstroms, c = 5.1514(2) Angstroms, = 102.758(2); Z = 16. At T = 321 K, a first-order phase transition occurs toward a monoclinic phase in space group P2{sub 1} with lattice parameters at T = 344 K of a = 10.3434(5) Angstroms, b = 5.8283(3) Angstroms, c = 5.1982(3) Angstroms, = 104.278(6); Z = (2). At T = 461 K, another phase transition, this time of second order, occurs toward an orthorhombic phase in space group Cmcm with lattice parameters at T = 510 K of a = 5.3069(2) Angstroms, b = 20.2423(10) Angstroms, c = 5.9479(2) Angstroms; Z = 4. As a common feature within all three crystal structures of rubidium triflate, the triflate anions are arranged in double layers with the lipophilic CF{sub 3} groups facing each other. The rubidium ions are located between the SO{sub 3} groups. The general packing is similar to the packing in cesium triflate. Rubidium triflate can be classified as a solid electrolyte with a specific ionic conductivity of = 9.89 x 10{sup -9} S/cm at T = 384 K and = 3.84 x 10{sup -6} S/cm at T = 481 K.

  8. RABL6A promotes G1-S phase progression and pancreatic neuroendocrine tumor cell proliferation in an Rb1-dependent manner

    PubMed Central

    Hagen, Jussara; Muniz, Viviane P.; Falls, Kelly; Reed, Sara M.; Taghiyev, Agshin F.; Quelle, Frederick W.; Gourronc, Francoise; Klingelhutz, Aloysius J.; Major, Heather J.; Askeland, Ryan; Sherman, Scott K.; O'Dorisio, Thomas M.; Bellizzi, Andrew M.; Howe, James R.; Darbro, Benjamin W.; Quelle, Dawn E.

    2014-01-01

    Mechanisms of neuroendocrine tumor (NET) proliferation are poorly understood and therapies that effectively control NET progression and metastatic disease are limited. We found amplification of a putative oncogene, RABL6A, in primary human pancreatic NETs(PNETs) that correlated with high level RABL6A protein expression. Consistent with those results, stable silencing of RABL6A in cultured BON-1 PNET cells revealed that it is essential for their proliferation and survival. Cells lacking RABL6A predominantly arrested in G1 phase with a moderate mitotic block. Pathway analysis of microarray data suggested activation of the p53 and retinoblastoma (Rb1) tumor suppressor pathways in the arrested cells. Loss of p53 had no effect on the RABL6A knockdown phenotype, indicating RABL6A functions independent of p53 in this setting. By comparison, Rb1 inactivation partially restored G1 to S phase progression in RABL6A knockdown cells although it was insufficient to override the mitotic arrest and cell death caused by RABL6A loss. Thus, RABL6A promotes G1 progression in PNET cells by inactivating Rb1, an established suppressor of PNET proliferation and development. This work identifies RABL6A as a novel negative regulator of Rb1 that is essential for PNET proliferation and survival. We suggest RABL6A is a new potential biomarker and target for anticancer therapy in PNET patients. PMID:25273089

  9. The superconducting transition temperatures of Fe1+xSe1-y, Fe1+xSe1-yTey and (K/Rb/Cs)zFe2-xSe2

    NASA Astrophysics Data System (ADS)

    Harshman, Dale R.; Fiory, Anthony T.

    2012-04-01

    In a recent contribution to this journal, it was shown that the transition temperatures of optimal high-TC compounds obey the algebraic relation {T}_{{C0}}={k}_{{B}}^{-1}\\beta /\\ell \\zeta , where ℓ is related to the mean spacing between interacting charges in the layers, ζ is the distance between interacting electronic layers, β is a universal constant and kB is Boltzmann’s constant. The equation was derived assuming pairing based on interlayer Coulomb interactions between physically separated charges. This theory was initially validated for 31 compounds from five different high-TC families (within an accuracy of ±1.37 K). Herein we report the addition of Fe1+xSe1-y and Fe1+xSe1-yTey (both optimized under pressure) and AzFe2-xSe2 (for A = K, Rb or Cs) to the growing list of Coulomb-mediated superconducting compounds in which TC0 is determined by the above equation. Doping in these materials is accomplished through the introduction of excess Fe and/or Se deficiency, or a combination of alkali metal and Fe vacancies. Consequently, a very small number of vacancies or interstitials can induce a superconducting state with a substantial transition temperature. The confirmation of the above equation for these Se-based Fe chalcogenides increases to six the number of superconducting families for which the transition temperature can be accurately predicted.

  10. New hypodiphosphates of the alkali metals: Synthesis, crystal structure and vibrational spectra of the hypodiphosphates(IV) M2[(H2P2O6)(H4P2O6)] (M=Rb and Cs)

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Wiegand, Thomas; Eckert, Hellmut; Gjikaj, Mimoza

    2012-10-01

    The new hypodiphosphates(IV) Rb2[(H2P2O6)(H4P2O6)] (1) and Cs2[(H2P2O6)(H4P2O6)] (2) were synthesized by soft chemistry reactions from aqueous solutions of hypophosphoric acid and the corresponding heavy alkali-metal carbonates. Their crystal structures were determined by single crystal X-ray diffraction. Both compounds crystallize isotypic in the triclinic space group P-1 with one formula unit in the unit cell. The structures are built up by discrete (H2P2O6)2- and (H4P2O6) units in staggered conformation for the P2O6 skeleton and the corresponding alkali-metal cations. In the (H2P2O6)2- ion the hydrogen atoms are in a "trans-trans" conformation. O·H-O hydrogen bonds between the (H2P2O6)2- and (H4P2O6) groups consolidate the structures into a three-dimensional network. The FT-Raman and 31P and 1H and MAS NMR spectra of the title compounds have been recorded and interpreted, especially with respect to their assignment to the (H2P2O6)2- and (H4P2O6) groups. Thermogravimetric data of 2 have been interpreted in terms of a thermal decomposition model.

  11. Q18Mg6(B5O10)3(B7O14)2F (Q = Rb and Cs): new borates containing two large isolated polyborate anions with similar topological structures.

    PubMed

    Wang, Zheng; Zhang, Min; Su, Xin; Pan, Shilie; Yang, Zhihua; Zhang, Hui; Liu, Lu

    2015-01-19

    Two novel isomorphic borates, Q18Mg6(B5O10)3(B7O14)2F (Q = Rb and Cs), were synthesized from high-temperature solutions. These borates are created from two kinds of isolated polyborate anionic groups, [B5O10] and [B7O14], and are further examples of two kinds of isolated polyborate anions coexisting in one borate structure. Although the title compounds are new structures, they are similar to the structures of the KBe2BO3F2 (KBBF) series of compounds, for example, Na2Be4B4O11 and γ-KBe2B3O7, which can be regarded as the substitution of [BO3] and [B2O5]/[B3O6] groups with [B7O14] and [B5O10] groups, respectively. It is found that the coexisting B-O groups tend to have similar structures. Also, the isolation of [B5O10] and [B7O14] in the title compounds mainly derives from the special role of magnesium tetrahedra, which has a similar role to that of the BeO4 tetrahedra in the KBBF series compounds. Electron-density maps and bond-overlap population (BOP) were calculated to illustrate this feature. PMID:25414057

  12. High-pressure optical absorption and x-ray-diffraction studies in RbI and KI approaching the metallization transition

    NASA Astrophysics Data System (ADS)

    Asaumi, K.; Suzuki, T.; Mori, T.

    1983-09-01

    The pressure dependence of the fundamental optical absorption edges in RbI and KI crystals has been investigated up to 70 GPa at room temperature by using high-pressure apparatus of sapphire and diamond anvil types. The absorption edges in RbI and KI are found to show some complicated behaviors below ~5 GPa within the uv region. Beyond ~5 GPa, absorption edges decrease monotonically with increasing pressure up to 70 GPa. The x-ray-diffraction study shows that the CsCl-type crystal structure remains stable up to 67 GPa after the NaCl- to CsCl-type phase transition at 0.4 GPa for RbI and at 1.9 GPa for KI, respectively. The metallization pressures of RbI and KI are estimated to be approximately 85 and 115 GPa, respectively.

  13. Phase separation in iron chalcogenide superconductor Rb0.8+xFe1.6+ySe2 as seen by Raman light scattering and band structure calculations

    NASA Astrophysics Data System (ADS)

    Pashkevich, Yu.; Gnezdilov, V.; Lemmens, P.; Shevtsova, T.; Gusev, A.; Lamonova, K.; Wulferding, D.; Gnatchenko, S.; Pomjakushina, E.; Conder, K.

    2016-06-01

    We report Raman light scattering in the phase separated superconducting single crystal Rb0.77Fe1.61Se2 with Tc = 32 K over a wide temperature region 3-500 K. The observed phonon lines from the majority vacancy ordered Rb2Fe4Se5 (245) antiferromagnetic phase with TN = 525 K demonstrate modest anomalies in the frequency, intensity and halfwidth at the superconductive phase transition. We identify phonon lines from the minority compressed RbδFe2Se2 (122) conductive phase. The superconducting gap with d x 2 - y 2 symmetry has been detected in our spectra. In the range 0-600 cm-1 we observe a weak but highly polarized B1g-type background which becomes well-structured upon cooling. A possible magnetic or multiorbital origin of this background is discussed. We argue that the phase separation in M0.8+xFe1.6+ySe2 is of pure magnetic origin. It occurs below the Néel temperature when the magnetic moment of iron reaches a critical value. We state that there is a spacer between the majority 245 and minority 122 phases. Using ab initio spin-polarized band structure calculations we demonstrate that the compressed vacancy ordered Rb2Fe4Se5 phase can be conductive and therefore may serve as a protective interface spacer between the purely metallic RbδFe2Se2 phase and the insulating Rb2Fe4Se5 phase providing percolative Josephson-junction like superconductivity all throughout of Rb0.8+xFe1.6+ySe2. Our lattice dynamics calculations show significant differences in the phonon spectra of the conductive and insulating Rb2Fe4Se5 phases.

  14. Synthesis and crystal structures of the layered uranyl tellurites A{sub 2}[(UO{sub 2}){sub 3}(TeO{sub 3}){sub 2}O{sub 2}] (A=K, Rb, Cs)

    SciTech Connect

    Woodward, Jonathan D.; Almond, Philip M.; Albrecht-Schmitt, Thomas E. . E-mail: albreth@auburn.edu

    2004-11-01

    The reactions of UO{sub 3} and TeO{sub 3} with KCl, RbCl, or CsCl at 800{sup o}C for 5d yield single crystals of A{sub 2}[(UO{sub 2}){sub 3}(TeO{sub 3}){sub 2}O{sub 2}] (A=K (1), Rb (2), and Cs (3)). These compounds are isostructural with one another, and their structures consist of two-dimensional {sub {infinity}}{sup 2}[(UO2)3(TeO3)2O2]2- sheets arranged in a stair-like topology separated by alkali metal cations. These sheets are comprised of zigzagging uranium(VI) oxide chains bridged by corner-sharing trigonal pyramidal TeO{sub 3}{sup 2-} anions. The chains are composed of dimeric, edge-sharing, pentagonal bipyramidal UO{sub 7} moieties joined by edge-sharing tetragonal bipyramidal UO{sub 6} units. The lone-pair of electrons from the TeO{sub 3} groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet non-polar. The alkali metal cations form contacts with nearby tellurite oxygen atoms as well as with oxygen atoms from the uranyl moieties. Crystallographic data (193K, MoK{alpha}, {lambda}=0.7107A): 1, triclinic, space group P1-bar , a=6.7985(5)A, b=7.0123(5)A, c=7.8965(6)A, {alpha}=101.852(1){sup o}, {beta}=102.974(1){sup o}, {gamma}=100.081(1){sup o}, V=349.25(4)A3, Z=2, R(F)=2.70% for 98 parameters and 1697 reflections with I>2{sigma}(I); 2, triclinic, space group P1-bar , a=7.0101(6)A, b=7.0742(6)A, c=8.0848(7)A, {alpha}=105.590(2){sup o}, {beta}=101.760(2){sup o}, {gamma}=99.456(2){sup o}, V=367.91(5)A3, Z=2, R(F)=2.36% for 98 parameters and 1817 reflections with I>2{sigma}(I); 3, triclinic, space group P1-bar , a=7.0007(5)A, b=7.5195(6)A, c=8.4327(6)A, {alpha}=109.301(1){sup o}, {beta}=100.573(1){sup o}, {gamma}=99.504(1){sup o}, V=399.49(5)A3, Z=2, R(F)=2.61% for 98 parameters and 1965 reflections with I>2{sigma}(I)

  15. X-ray powder diffraction, vibration and thermal studies of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb: Influence of mixed cationic and anionic substitutions

    SciTech Connect

    Aribia, W. Ben; Abdelmouleh, M.; Kabadou, A.; Van Der Lee, A.

    2012-05-15

    Graphical abstract: The structures of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb belong to the tetragonal {beta}-K{sub 2}SnCl{sub 6} structure type. Highlights: Black-Right-Pointing-Pointer The two new compound crystallises in P4/mnc tetragonal space group. Black-Right-Pointing-Pointer The structure is considered as isolated octahedred TeCl{sub 4}Br{sup 2-}. Black-Right-Pointing-Pointer The octahedra connected by ionic and hydrogen bonding through the Cs/Rb or N atoms. Black-Right-Pointing-Pointer A DTA/TGA experiment reveals one endothermic peak at 780 K for these compounds. Black-Right-Pointing-Pointer One endothermic peak is detected at around 213 K by DSC experiment. -- Abstract: The crystal structures of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb have been determined using X-ray powder diffraction techniques. The two compounds crystallize in the tetragonal space group P4/mnc, with the unit cell parameters: a = 7.452(1) Angstrom-Sign , c = 10.544(3) Angstrom-Sign , Z = 2 and a = 7.315(2) Angstrom-Sign , c = 10.354(4) Angstrom-Sign , Z = 2 in the presence of Cs and Rb, respectively. These two compounds have an antifluorite-type arrangement of NH{sub 4}{sup +}/Rb{sup +}/Cs{sup +} and octahedral TeCl{sub 4}Br{sub 2}{sup 2-} anions. The stability of these structure is by ionic and hydrogen bonding contacts: A Midline-Horizontal-Ellipsis Cl, A Midline-Horizontal-Ellipsis Br and N-H Midline-Horizontal-Ellipsis Cl, N-H Midline-Horizontal-Ellipsis Br. The different vibrational modes of these powders were analysed by FTIR and Raman spectroscopic studies. A DTA/TGA experiment reveals one endothermic peak at 780 K implicating the decomposition of the sample. At low temperature, one endothermic peak in thermal behavior is detected at around 213 K by DSC experiment. This transition was confirmed by dielectric measurements.

  16. Structures of Hydrated Alkali Metal Cations, M+(H2O)nAr (m = Li, Na, K, rb and Cs, n = 3-5), Using Infrared Photodissociation Spectroscopy and Thermodynamic Analysis

    NASA Astrophysics Data System (ADS)

    Ke, Haochen; van der Linde, Christian; Lisy, James M.

    2014-06-01

    Alkali metal cations play vital roles in chemical and biochemical systems. Lithium is widely used in psychiatric treatment of manic states and bipolar disorder; Sodium and potassium are essential elements, having major biological roles as electrolytes, balancing osmotic pressure on body cells and assisting the electroneurographic signal transmission; Rubidium has seen increasing usage as a supplementation for manic depression and depression treatment; Cesium doped compounds are used as essential catalysts in chemical production and organic synthesis. Since hydrated alkali metal cations are ubiquitous and the basic form of the alkali metal cations in chemical and biochemical systems, their structural and thermodynamic properties serve as the foundation for modeling more complex chemical and biochemical processes, such as ion transport and ion size-selectivity of ionophores and protein channels. By combining mass spectrometry and infrared photodissociation spectroscopy, we have characterized the structures and thermodynamic properties of the hydrated alkali metal cations, i.e. M+(H2O)nAr, (M = Li, Na, K, Rb and Cs, n = 3-5). Ab initio calculations and RRKM-EE (evaporative ensemble) calculations were used to assist in the spectral assignments and thermodynamic analysis. Results showed that the structures of hydrated alkali metal cations were determined predominantly by the competition between non-covalent interactions, i.e. the water---water hydrogen bonding interactions and the water---cation electrostatic interactions. This balance, however, is very delicate and small changes, i.e. different cations, different levels of hydration and different effective temperatures clearly impact the balance.

  17. Two spatially separated phases in semiconducting Rb0.8Fe1.5S2

    SciTech Connect

    Wang, Meng; Tian, Wei; Valdivia, P.; Chi, Songxue; Bourret-Courchesne, E.; Dai, Pengcheng; Birgeneau, R. J.

    2014-09-26

    We report neutron scattering and transport measurements on semiconducting Rb0.8Fe1.5S2, a compound isostructural and isoelectronic to the well-studied A0.8FeySe2(A = K, Rb, Cs, Tl/K) superconducting systems. Both resistivity and DC susceptibility measurements reveal a magnetic phase transition at T = 275 K. Neutron diffraction studies show that the 275 K transition originates from a phase with rhombic iron vacancy order which exhibits an in-plane stripe antiferromagnetic ordering below 275 K. In addition, the stripe antiferromagnetic phase interdigitates mesoscopically with an ubiquitous phase with √5 x√5 iron vacancy order. This phase has a magnetic transition at TN = 425 K and an iron vacancy order-disorder transition at TS = 600 K. These two different structural phases are closely similar to those observed in the isomorphous Se materials. Based on the close similarities of the in-plane antiferromagnetic structures, moments sizes, and ordering temperatures in semiconducting Rb0.8Fe1.5S2 and K0.81Fe1.58Se2, we argue that the in-plane antiferromagnetic order arises from strong coupling between local moments. Superconductivity, previously observed in the A0.8FeySe2₋ zSz system, is absent in A0.8Fe1.5S2, which has a semiconducting ground state. We discuss the implied relationship between stripe and block antiferromagnetism and superconductivity in these materials as well as a strategy for further investigation.

  18. Raman Spectroscopic Investigation of the Superionic Phase Transition in Cs3D(SO4)2

    NASA Astrophysics Data System (ADS)

    Matsumoto, Yoshiyuki; Kakuma, Takayuki; Muta, Shinnosuke

    2016-06-01

    The superionic phase transition of Cs3D(SO4)2 (TCDS) is investigated using Raman scattering and differential scanning calorimetry (DSC) measurements. It is confirmed that TCDS undergoes a superionic phase transition at 415.1 K. The result of the Raman scattering measurement at room temperature shows that TCDS does not form the dimer structure SO4⋯D⋯SO4. It suggests that this phase transition is not caused by the destruction of hydrogen bonds forming a dimer structure.

  19. Elastic constants and ultrasound attenuation in the spin-liquid phase of Cs2CuCl4

    NASA Astrophysics Data System (ADS)

    Streib, Simon; Kopietz, Peter; Cong, Pham Thanh; Wolf, Bernd; Lang, Michael; van Well, Natalija; Ritter, Franz; Assmus, Wolf

    2015-03-01

    The spin excitations in the spin-liquid phase of the anisotropic triangular lattice quantum antiferromagnet Cs2CuCl4 have been shown to propagate dominantly along the crystallographic b-axis. To test this dimensional reduction scenario, we have performed ultrasound experiments in the spin-liquid phase of Cs2CuCl4 probing the elastic constant c22 and the sound attenuation along the b-axis as a function of an external magnetic field along the a-axis. We show that our data can be quantitatively explained within the framework of a nearest neighbor spin- 1 / 2 Heisenberg chain, where fermions are introduced via the Jordan-Wigner transformation and the spin-phonon interaction arises from the usual exchange-striction mechanism. Financial support by the DFG via SFB/TRR49 is gratefully acknowledged.

  20. Phase I Imaging and Pharmacodynamic Trial of CS-1008 in Patients With Metastatic Colorectal Cancer

    PubMed Central

    Ciprotti, Marika; Tebbutt, Niall C.; Lee, Fook-Thean; Lee, Sze-Ting; Gan, Hui K.; McKee, David C.; O'Keefe, Graeme J.; Gong, Sylvia J.; Chong, Geoffrey; Hopkins, Wendie; Chappell, Bridget; Scott, Fiona E.; Brechbiel, Martin W.; Tse, Archie N.; Jansen, Mendel; Matsumura, Manabu; Kotsuma, Masakatsu; Watanabe, Rira; Venhaus, Ralph; Beckman, Robert A.; Greenberg, Jonathan; Scott, Andrew M.

    2015-01-01

    Purpose CS-1008 (tigatuzumab) is a humanized, monoclonal immunoglobulin G1 (IgG1) agonistic antibody to human death receptor 5. The purpose of this study was to investigate the impact of CS-1008 dose on the biodistribution, quantitative tumor uptake, and antitumor response in patients with metastatic colorectal cancer (mCRC). Patients and Methods Patients with mCRC who had received at least one course of chemotherapy were assigned to one of five dosage cohorts and infused with a weekly dose of CS-1008. Day 1 and day 36 doses were trace-labeled with indium-111 (111In), followed by whole-body planar and regional single-photon emission computed tomography (SPECT) imaging at several time points over the course of 10 days. Results Nineteen patients were enrolled. 111In-CS-1008 uptake in tumor was observed in only 12 patients (63%). 111In-CS-1008 uptake and pharmacokinetics were not affected by dose or repeated drug administration. 111In-CS-1008 biodistribution showed gradual blood-pool clearance and no abnormal uptake in normal tissue. No anti–CS-1008 antibody development was detected. One patient achieved partial response (3.7 months duration), eight patients had stable disease, and 10 patients had progressive disease. Clinical benefit rate (stable disease + partial response) in patients with 111In-CS-1008 uptake in tumor was 58% versus 28% in patients with no uptake. An analysis of individual lesions showed that lesions with antibody uptake were one third as likely to progress as those without antibody uptake (P = .07). Death-receptor–5 expression in archived tumor samples did not correlate with 111In-CS-1008 uptake (P = .5) or tumor response (P = .6). Conclusion Death-receptor–5 imaging with 111In-CS-1008 reveals interpatient and intrapatient heterogeneity of uptake in tumor, is not dose dependent, and is predictive of clinical benefit in the treatment of patients who have mCRC. PMID:26124477

  1. Synthesis and structural characterization of AMV2O8 (A = K, Rb, Tl, Cs; M = Nb, Ta) vanadates: a structural comparison of A(+)M(5+)V2O8 vanadates and A(+)M(5+)P2O8 phosphates.

    PubMed

    Paidi, Anil Kumar; Devi, R Nandini; Vidyasagar, Kanamaluru

    2015-10-21

    Eight new quaternary vanadates of niobium and tantalum, AMV2O8 (A = K, Rb, Tl, Cs; M = Nb, Ta), have been prepared by solid state reactions and structurally characterized by single crystal and powder X-ray diffraction (XRD) techniques. The two cesium compounds, unlike the known CsSbV2O8 with a layered yavapaiite structure, have a new three-dimensional structure and the other six compounds possess the known KSbV2O8 structure type. The three types of [(MV2O8)(-)]∞ anionic frameworks of twelve A(+)M(5+)V2O8 (A = K, Rb, Tl, Cs; M = Nb, Ta, Sb) vanadates could be conceived to be built by different connectivity patterns of M2V4O18 ribbons, which contain MO6 octahedra and VO4 tetrahedra. A structural comparison of these twelve vanadates and the nineteen A(+)M(5+)P2O8 phosphates has been made. The spectroscopic studies of these eight new quaternary vanadates are presented. PMID:26390384

  2. Pressure-induced phase transition of Cs 2 (TCNQ) 3 crystals revealed by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsuzaki, S.; Matsushita, Y.; Sano, M.

    1990-06-01

    The pressure dependence of the C= C stretching vibrations was studied for Cs 2(TCNQ) 3, which has trimeric stacks with localized electrons on the specific TCNQ sites at ambient pressure. Two Raman bands of the neutral and ionic TCNQ sites are found to merge discontinously to a single band at 43 kbar. The spectral change suggests delocalization of the conduction electrons.

  3. Epitaxial growth of hexagonal tungsten bronze Cs x WO3 films in superconducting phase region exceeding bulk limit

    NASA Astrophysics Data System (ADS)

    Soma, Takuto; Yoshimatsu, Kohei; Ohtomo, Akira

    2016-07-01

    We report epitaxial synthesis of superconducting Cs x WO3 (x = 0.11, 0.20, and 0.31) films on Y-stabilized ZrO2 (111) substrates. The hexagonal crystal structure was verified not only for the composition within the stable region of the bulk (x = 0.20 and 0.31), but also for the out-of-range composition (x = 0.11). The onset of the superconducting transition was recorded at 5.8 K for x = 0.11. We found a strong correlation between the superconducting transition temperature (T C) and the c-axis length, irrespective of the Cs content. These results indicated that the hidden superconducting phase region of hexagonal tungsten bronze is accessible using epitaxial synthesis of lightly doped films.

  4. Status of U.S./Japan collaborative program phase II HFIR target and RB{sup *} capsules

    SciTech Connect

    Pawel, J.E.; Lenox, K.E.; Longest, A.W.

    1995-04-01

    The objective of the HFIR irradiations is to determine the response of various U.S. and Japanese austenitic and ferritic steels with different pretreatments and alloy compositions to the combined effects of displacement damage and helium generation. Specimen temperatures during irradiation range from 60 to 600{degrees}C and fluences range up to 60 dpa. The RB{sup *} experiments are a continuation of the ORR spectrally tailored experiments in which the spectrum is modified with a hafnium shield to simulate the expected fusion helium to damage (He/dpa) ratio. In the HFIR target capsules, many specimens have been isotopically tailored in order to achieve fusion helium generation rates.

  5. Polymeric fullerene chains in RbC60 and KC60

    NASA Astrophysics Data System (ADS)

    Stephens, Peter W.; Bortel, G.; Faigel, G.; Tegze, M.; Jánossy, A.; Pekker, S.; Oszlanyi, G.; Forró, L.

    1994-08-01

    NEARLY all of the molecular crystals containing C60, formed at ambient pressure1,2 have inter-fullerene separations of the order of 10 Å - the expected distance based on the molecular van der Waals radii. The sole exceptions are the room-temperature phases of AC60 (where A denotes K, Rb or Cs), which are formed by reversible solid-state transformation from high-temperature (>150 °C) phases3. These phases have lattice parameters about 9% shorter in one direction, and in addition RbC60 has magnetic properties suggestive of a one-dimensional metal4. We suggested in ref. 4 that this short distance may be due to covalent bonding between neighbouring C60 molecules. Here we provide direct evidence for such bonding from powder X-ray diffraction studies of RbC60 and KC60 . The linkage is through a [2+2] cycloaddition, which has been hypothesized to take place during photopolymerization of solid C60 (ref. 5), and which has also been proposed6 for RbC60. Such inter-fullerene linkages are calculated7,8 to be the preferred mode of dimerization of C60. The AC60 phases thus provide an example of a thermal phase transition driven by the reversible formation and breaking of covalent bonds.

  6. Guided ion beam and theoretical studies of the reaction of Ag{sup +} with CS{sub 2}: Gas-phase thermochemistry of AgS{sup +} and AgCS{sup +} and insight into spin-forbidden reactions

    SciTech Connect

    Armentrout, P. B.; Kretzschmar, Ilona

    2010-01-14

    The gas-phase reactivity of the atomic transition metal cation, Ag{sup +}, with CS{sub 2} is investigated using guided-ion beam mass spectrometry. Endothermic reactions forming AgS{sup +} and AgCS{sup +} are observed but are quite inefficient. This observation is largely attributed to the stability of the closed shell Ag{sup +}({sup 1}S,4d{sup 10}) ground state, but is also influenced by the fact that the reactions producing ground state AgS{sup +} and AgCS{sup +} products are both spin forbidden. Analysis of the kinetic energy dependence of the cross sections for formation of these two products yields the 0 K bond energies of D{sub 0}(Ag{sup +}-S)=1.40{+-}0.12 eV and D{sub 0}(Ag{sup +}-CS)=1.98{+-}0.14 eV. Quantum chemical calculations are used to investigate the electronic structure of the two product ions as well as the potential energy surfaces for reaction. The primary mechanism involves oxidative addition of a CS bond to the metal cation followed by simple Ag-S or Ag-CS bond cleavage. Crossing points between the singlet and triplet surfaces are located near the transition states for bond activation. Comparison with analogous work on other late second-row transition metal cations indicates that the location of the crossing points bears directly on the efficiency of these spin-forbidden processes.

  7. Structural study of the high-pressure antiferroelectric phase of CsH/sub 2/PO/sub 4/

    SciTech Connect

    Schuele, P.J.; Thomas, R.

    1985-01-01

    A three-dimensional neutron diffraction study has been carried out on the pressure-induced antiferroelectric phase of CsH/sub 2/PO/sub 4/. At 100.7/sup 0/K and a hydrostatic pressure of 3.6 kbar, the unit cell parameters are a = 15.625(9), b = 6.254(2), c = 4.886(1) A, ..beta.. = 108.08(3)/sup 0/ and Z = 4. Atomic parameters were determined using full-matrix least-squares methods which yield final agreement indices: R(F/sup 2/) = 0.0715, R/sub w/(F/sup 2/) = 0.0807 and S = 2.13. The structure is nearly consistent with the monoclinic space group P2/sub 1//a but refinement in P2/sub 1/ yields a slightly better fit. The structure is markedly different from those of the paraelectric and ferroelectric phases with large relative displacements (nearly 1 A) of Cs/sup +1/ and PO/sub 4//sup -3/ groups in the x-z plane. Hydrogens bonding in b-chains, which are disordered in the paraelectric phase, show antiferroelectric order.

  8. Field-induced phase transitions and magnetoferroelectricity in the perfect triangular lattice antiferromagnet RbFe(MoO4)2 in a vertical magnetic field

    NASA Astrophysics Data System (ADS)

    Mitamura, Hiroyuki; Watanuki, Ryuta; Onozaki, Norimichi; Amou, Yuta; Kono, Yohei; Kittaka, Shunichiro; Shimura, Yasuyuki; Yamamoto, Isao; Suzuki, Kazuya; Sakakibara, Toshiro

    2016-02-01

    We performed electric polarization P, dielectric constant ɛ and magnetization M measurements on the perfect triangular-lattice antiferromagnet RbFe(MoO4)2 in high magnetic fields B applied along the c-axis. Whereas M(B) at T=1.5 K monotonically increases with B up to the saturation at Bs = 21 T, P(B) disappears about 14 T, far below the saturation point. In a field range 13 ≤ B ≤ 14 T, the temperature variation of ɛ shows a double peak structure below 2.8 K, indicating two successive transitions. These results strongly suggest the presence of a new high-field phase; the magnetic structure changes from a low-field conical state having chirality to a high-field coplanar non-collinear structure without chirality. The obtained phase diagram is in agreement with a theoretical prediction on XY-like Heisenberg spin triangular lattice antiferromagnets.

  9. Temperature and composition phase diagram in the iron-based ladder compounds Ba 1 - x Cs x Fe 2 Se 3

    DOE PAGESBeta

    Hawai, Takafumi; Nambu, Yusuke; Ohgushi, Kenya; Du, Fei; Hirata, Yasuyuki; Avdeev, Maxim; Uwatoko, Yoshiya; Sekine, Yurina; Fukazawa, Hiroshi; Ma, Jie; et al

    2015-05-28

    We investigated the iron-based ladder compounds (Ba,Cs)Fe₂Se₃. Their parent compounds BaFe₂Se₃ and CsFe₂Se₃ have different space groups, formal valences of Fe, and magnetic structures. Electrical resistivity, specific heat, magnetic susceptibility, x-ray diffraction, and powder neutron diffraction measurements were conducted to obtain a temperature and composition phase diagram of this system. Block magnetism observed in BaFe₂Se₃ is drastically suppressed with Cs doping. In contrast, stripe magnetism observed in CsFe₂Se₃ is not so fragile against Ba doping. A new type of magnetic structure appears in intermediate compositions, which is similar to stripe magnetism of CsFe₂Se₃, but interladder spin configuration is different. Intermediatemore » compounds show insulating behavior, nevertheless a finite T-linear contribution in specific heat was obtained at low temperatures.« less

  10. Leucine-responsive regulatory protein Lrp and PapI homologues influence phase variation of CS31A fimbriae.

    PubMed

    Graveline, Richard; Garneau, Philippe; Martin, Christine; Mourez, Michaël; Hancock, Mark A; Lavoie, Rémi; Harel, Josée

    2014-08-15

    CS31A, a K88-related surface antigen specified by the clp operon, is a member of the type P family of adhesive factors and plays a key role in the establishment of disease caused by septicemic and enterotoxigenic Escherichia coli strains. Its expression is under the control of methylation-dependent transcriptional regulation, for which the leucine-responsive regulatory protein (Lrp) is essential. CS31A is preferentially in the OFF state and exhibits distinct regulatory features compared to the regulation of other P family members. In the present study, surface plasmon resonance and DNase I protection assays showed that Lrp binds to the distal moiety of the clp regulatory region with low micromolar affinity compared to its binding to the proximal moiety, which exhibits stronger, nanomolar affinity. The complex formation was also influenced by the addition of PapI or FooI, which increased the affinity of Lrp for the clp distal and proximal regions and was required to induce phase variation. The influence of PapI or FooI, however, was predominantly associated with a more complete shutdown of clp expression, in contrast to what has previously been observed with AfaF (a PapI ortholog). Taken together, these results suggest that the preferential OFF state observed in CS31A cells is mainly due to the weak interaction of the leucine-responsive regulatory protein with the clp distal region and that the PapI homolog favors the OFF phase. Within the large repertoire of fimbrial variants in the P family, our study illustrates that having a fimbrial operon that lacks its own PapI ortholog allows it to be more flexibly regulated by other orthologs in the cell. PMID:24914179

  11. Thermoelectric properties of homogeneously and non-homogeneously doped CdTe15/16M1/16 (M=N, P, As, Sb) and Cd15/16TeM1/16 (M=Na, K, Rb, Cs)

    NASA Astrophysics Data System (ADS)

    Yang, X. H.; Qin, X. Y.; Li, D.; Zhang, J.; Song, C. J.; Liu, Y. F.; Wang, L.; Xin, H. X.

    2015-11-01

    The electrical transport properties of p-doped semiconductors CdTe15/16M1/16 (M=N, P, As, Sb) and Cd15/16TeM1/16 (M=Na, K, Rb, Cs) with two configurations are investigated through first-principles calculations combined with Boltzmann transport theory under the relaxation time approximation. It is found that N and Cs atoms in the homogeneous structure induce much sharper electron densities of states (DOSs) and flatter energy bands at the valence band edges than the rest of doped elements, resulting in much larger Seebeck coefficients. The calculations reveal that most of the Seebeck coefficients and electrical conductivities are impacted unfavorably by the conglomeration of impurity atoms considered. Though the power factors for homogeneous doping of N and Cs are comparatively smaller, the electronic figures of merit are much larger at 800-1000 K than the rest ones due to much smaller electronic thermal conductivities, therefore probably enhancing the thermoelectric figures of merit. The results show that doping the elements with electronegativities distinct from the host atoms can enhance the Seebeck coefficients and the thermoelectric performances of bulk semiconductors efficiently if the energy levels of doped atoms resonate with those of host atoms and the arrangement of doped atoms is modulated appropriately to avoid deteriorating the sharpness of the DOS (or transport distribution).

  12. Pressure-induced phase transitions in rubidium azide: Studied by in-situ x-ray diffraction

    SciTech Connect

    Li, Dongmei; Wu, Xiaoxin; Jiang, Junru; Zhang, Jian; Cui, Qiliang; Zhu, Hongyang; Wang, Xiaoli

    2014-08-18

    We present the in-situ X-ray diffraction studies of RbN{sub 3} up to 42.0 GPa at room temperature to supplement the high pressure exploration of alkali azides. Two pressure-induced phase transitions of α-RbN{sub 3} → γ-RbN{sub 3} → δ-RbN{sub 3} were revealed at 6.5 and 16.0 GPa, respectively. During the phase transition of α-RbN{sub 3} → γ-RbN{sub 3}, lattice symmetry decreases from a fourfold to a twofold axis accompanied by a rearrangement of azide anions. The γ-RbN{sub 3} was identified to be a monoclinic structure with C2/m space group. Upon further compression, an orthogonal arrangement of azide anions becomes energetically favorable for δ-RbN{sub 3}. The compressibility of α-RbN{sub 3} is anisotropic due to the orientation of azide anions. The bulk modulus of α-RbN{sub 3} is 18.4 GPa, quite close to those of KN{sub 3} and CsN{sub 3}. By comparing the phase transition pressures of alkali azides, their ionic character is found to play a key role in pressure-induced phase transitions.

  13. First Principles Study of the Vibrational and Thermal Properties of the Type-II Clathrates AxGaxSn136-x(x = 8,16,24; A = Rb,Cs)

    NASA Astrophysics Data System (ADS)

    Xue, Dong; Myles, Charles

    2015-03-01

    We have performed first-principles calculations of the vibrational and thermal properties of the semiconductor clathrates RbxGaxSn136-x and CsxGaxSn136-x for x = 8, 16, and 24. Our calculations used the VASP code to obtain the equilibrium geometries and the PHONOPY code to obtain the harmonic phonon modes. For x = 24, the phonon dispersion relations predict an upshift of the low-lying optical modes (<30cm-1) in the presence of the light guest (``rattler'') Rb. We also find large isotropic atomic displacement parameters (Uiso) when the Rb occupies the large cages (Sn28) . The modes associated with these guests should contribute strongly to lowering the lattice thermal conductivity (kL) . This is reinforced by our evaluation of the guest-associated effective potential energy curves E(x). Our calculated effective harmonic spring constants K for these guests show that a simple harmonic oscillator model is in good agreement with the first principles lattice dynamical calculations. The similarity between ωos = (K/M)1/2 and our computed guest phonon frequencies implies that anharmonic contributions to the guest vibrational modes are not significant. Our calculations of the vibrational contribution to the specific heat and our estimation of kLare also presented and discussed.

  14. High temperature synthesis of two open-framework uranyl silicates with ten-ring channels: Cs{sub 2}(UO{sub 2}){sub 2}Si{sub 8}O{sub 19} and Rb{sub 2}(UO{sub 2}){sub 2}Si{sub 5}O{sub 13}

    SciTech Connect

    Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

    2013-01-15

    The uranyl silicates Cs{sub 2}(UO{sub 2}){sub 2}Si{sub 8}O{sub 19} and Rb{sub 2}(UO{sub 2}){sub 2}Si{sub 5}O{sub 13} were obtained by mixing stoichiometric amounts of uranium metal, tellurium dioxide, silicon dioxide, and an excess of correspondent alkali metal halide flux. These compounds crystallize in the orthorhombic space groups Pnma and C222 with eight and two units per unit cell, respectively. Their crystal structures are dominated by zippered pentagonal bipyramidal chains of UO{sub 7} and silicates layer that are further connected into 3D frameworks. The cesium compound has silicate double layers while rubidium has a single layer. Six-ring voids and ten-ring channels are found in both compounds. - Graphical abstract: A view of the three-dimensional network structure of Cs{sub 2}(UO{sub 2}){sub 2}Si{sub 8}O{sub 19}. Highlights: Black-Right-Pointing-Pointer Three-dimensional uranium silicates. Black-Right-Pointing-Pointer Analogs of natural uranyl silicate minerals. Black-Right-Pointing-Pointer Complexity and symmetry ambiguity of uranyl silicates.

  15. Comparative study of A-site order in the lead-free bismuth titanates M{sub 1/2}Bi{sub 1/2}TiO{sub 3} (M=Li, Na, K, Rb, Cs, Ag, Tl) from first-principles

    SciTech Connect

    Gröting, Melanie Albe, Karsten

    2014-05-01

    We investigate the possibility of enhancing chemical order in the relaxor ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} upon substitution of Na{sup +} by other monovalent cations M{sup +} using total energy calculations based on density functional theory. All chemically available monovalent cations M{sup +}, which are Li, Na, Ag, K, Tl, Rb and Cs, are considered and an analysis of the structurally relaxed structures in terms of symmetry-adapted distortion modes is given in order to quantify the chemically induced structural distortions. We demonstrate that the replacement of Na{sup +} by other monovalent cations can hardly alter the tendency of chemical order with respect to Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}. Only Tl{sub 1/2}Bi{sub 1/2}TiO{sub 3} and Ag{sub 1/2}Bi{sub 1/2}TiO{sub 3} show enhanced tendency for chemical ordering. Both heavy metals behave similar to the light alkali metals in terms of structural relaxations and relative stabilities of the ordered configurations. Although a comparison of the Goldschmidt factors of components (M TiO{sub 3}){sup −} reveals for Tl a value above the upper stability limit for perovskites, the additional lone-pair effect of Tl{sup +} stabilizes the ordered structure. - Graphical abstract: Amplitudes of chemically induced distortion modes in different ordered perovskites M{sub 1/2}Bi{sub 1/2}TiO{sub 3} and visualisation of atomic displacements associated with distortion mode X{sup +}{sub 1} in the 001-ordered compounds Li{sub 1/2}Bi{sub 1/2}TiO{sub 3} and Cs{sub 1/2}Bi{sub 1/2}TiO{sub 3}. Due to a substantial size mismatch between bismuth (green) and caesium (dark blue), incorporation of the latter leads to enhanced displacements of oxygen atoms (red) and suppresses displacements of titanium (silver) as compared to lithium (light blue) or other smaller monovalent cations. - Highlights: • Lead-free A-site mixed bismuth titanates M{sub 1/2}Bi{sub 1/2}TiO{sub 3} are studied by first-principles calculations. • Investigation

  16. Surface science of Cs, CsO and CsI ionic layers on Pt(111)

    NASA Astrophysics Data System (ADS)

    Drnec, Jakub

    Cesium adsorption on Pt(111) and its coadsorption with iodine and oxygen is studied in this dissertation. The work function during Cs dosing first decreases and at Deltaφ ≈ 3 eV (thetaCs = 0.15) the surface undergoes surface transition between a disordered anomalous state (Pt(111)(anom)-Cs) and islands of a Pt(111)(2x2)-Cs causing a change in the slope of the work function curve. The work function curve reaches minimum at --5.5 eV where the surface is fully covered with the Pt(111)(2 x 2)-Cs structure( thetaCs = 0.25). Further Cs dosing results in a work function increase and the surface undergoes a phase transition to Pt(111)(√3 x√3)-Cs. The Cs saturated structure (Pt(111)(ihcp)-Cs) has an hexagonal symmetry with the unit cell vector aligned with the (1, 0) direction of the substrate. Cs in the anomalous state desorbs from the surface in a high-temperature TDS peak (> 1000 K). When the lock-in TDS detection technique is used, this peak appears to be phase shifted by 180° when compared to the desorption peak of normally adsorbed Cs (thetaCs> 0.15) . This phase shift is a consequence of a positive charge of desorbing Cs. The TDS and work function behavior were explained by a Monte Carlo desorption model incorporating di¤erent desorption behavior for all four observed adsorption phases. When O2 is dosed on a Pt(111)-Cs surface, the maximum coverage of oxygen bonded to the surface is signi.cantly increased in comparison to Pt(111). Anomalously adsorbed Cs activates the O2 bond but does not interact strongly with coadsorbed O. However, when O2 is dosed on Pt(111)(ihcp)-Cs, the oxygen first adsorbs to a sub-layer adsorption site and strongly interacts with Cs. The oxygen in this state is responsible for thermal stabilization of coadsorbed Cs. When iodine is coadsorbed on a Pt(111)-Cs surface, it also strongly interacts with and thermally stabilizes Cs. During the desorption of Cs,I layers, some Cs and I desorb together in the form of a CsxIy cluster. The

  17. On the high-temperature phase transitions of CsH2PO4: A polymorphic transition? A transition to a superprotonic conducting phase?

    NASA Astrophysics Data System (ADS)

    Ortiz, E.; Vargas, R. A.; Mellander, B.-E.

    1999-03-01

    X-ray diffraction, thermogravimetric (TGA), differential scanning calorimetric (DSC), and impedance analysis were used to study the reported high-temperature phase transitions at 107, 149, 230, and 256 °C in crystals of cesium dihydrogen phosphate, CsH2PO4 (CDP). Our results show strong evidence that at all these temperatures, the observed DSC or differential thermal analysis (DTA) endothermic effects appear only as a consequence of a dehydration process starting on the surface of the crystal. Our results thus show that the reported transition at 230 °C is not a polymorphic transition. This means that the monoclinic symmetry, stable at room temperature, with space group P21/m-C2k2, is maintained up to the final decomposition. Moreover, since we have not found any evidence for the existence of a superprotonic high-temperature phase above 230 °C, the high conductivity above 230 °C is thus only a consequence of the dehydration of the crystal surface.

  18. Magnetic decoupling studies of Rb relaxation in Xe

    NASA Astrophysics Data System (ADS)

    Griffith, W. M.; Walter, D. K.; Happer, W.

    2001-05-01

    We present the results of extensive experiments on the relaxation of ^85Rb and ^87Rb due to gas-phase interactions with Xe in the presence of third-body gases in the pressure range from tens of torr to more than an atmosphere. By studying the relaxation as a function of applied magnetic field from 0 to 6000 G, we are able to separate the Rb relaxation into contributions from Rb--Xe binary collisions and from Rb--Xe van der Waals molecules. We have determined to high accuracy the strength of the Rb--Xe spin-rotation coupling constant, and we report the temperature dependences of the Rb--Xe binary relaxation cross section, the molecular formation rate, and the molecular break-up rate.

  19. CsSnI3: Semiconductor or metal? High electrical conductivity and strong near-infrared photoluminescence from a single material. High hole mobility and phase-transitions.

    PubMed

    Chung, In; Song, Jung-Hwan; Im, Jino; Androulakis, John; Malliakas, Christos D; Li, Hao; Freeman, Arthur J; Kenney, John T; Kanatzidis, Mercouri G

    2012-05-23

    CsSnI(3) is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI(3) have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI(3), coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI(3). The black orthorhombic form of CsSnI(3) demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI(3) indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of ∼ 10(17) cm(-3) and a hole mobility of ∼585 cm(2) V(-1) s(-1). The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from Sn defects in the crystal structure, which arise

  20. Alkali metal and ammonium fluoro(trifluoroacetato)metallates M Prime [M Prime Prime {sub 3}({mu}{sub 3}-F)(CF{sub 3}COO){sub 6}(CF{sub 3}COOH){sub 3}], where M Prime = Li, Na, K, NH{sub 4}, Rb, or Cs and M Prime Prime = Ni or Co. Synthesis and crystal structures

    SciTech Connect

    Tereshchenko, D. S.; Morozov, I. V. Boltalin, A. I.; Karpova, E. V.; Glazunova, T. Yu.; Troyanov, S. I.

    2013-01-15

    A series of fluoro(trifluoroacetato)metallates were synthesized by crystallization from solutions in trifluoroacetic acid containing nickel(II) or cobalt(II) nitrate hydrates and alkali metal or ammonium fluorides: Li[Ni{sub 3}({mu}{sub 3}-F)(CF{sub 3}COO){sub 6}(CF{sub 3}COOH){sub 3}](CF{sub 3}COOH){sub 3} (I), M Prime [Ni{sub 3}({mu}{sub 3}-F)(CF{sub 3}COO){sub 6}(CF{sub 3}COOH){sub 3}] (M Prime = Na (II), NH{sub 4} (IV), Rb (V), and Cs (VI)), NH{sub 4}[Co{sub 3}({mu}{sub 3}-F) (CF{sub 3}COO){sub 6}(CF{sub 3}COOH){sub 3}] (III), and Cs[Ni{sub 3}({mu}{sub 3}-F)(CF{sub 3}COO){sub 6}(CF{sub 3}COOH){sub 3}](CF{sub 3}COOH){sub 0.5} (VII). The crystal structures of these compounds were determined by single-crystal X-ray diffraction. All structures contain triangular trinuclear complex anions [M{sub 3} Double-Prime ({mu}{sub 3}-F)(CF{sub 3}COO){sub 6}(CF{sub 3}COOH){sub 3}]{sup -} (M Double-Prime = Ni, Co) structurally similar to trinuclear 3d metal oxo carboxylate complexes. The three-coordinated F atom is located at the center of the triangle formed by Ni(II) or Co(II) atoms. The metal atoms are linked in pairs by six bridging trifluoroacetate groups located above and below the plane of the [M Double-Prime {sub 3} F] triangle. The oxygen atoms of the axial CF{sub 3}COOH molecules complete the coordination environment of M Double-Prime atoms to an octahedron.

  1. Characterization of the Natural Organic Matter (NOM) in groundwater contaminated with (60)Co and (137)Cs using ultrafiltration, Solid Phase Extraction and fluorescence analysis.

    PubMed

    Caron, François; Siemann, Stefan; Riopel, Rémi

    2014-12-01

    Spot samples of shallow groundwaters have been taken between the years 2004 and 2010 near a site formerly used for the dispersal of radioactive liquid wastes. Three sampling points, one clean (upstream), and two downstream of the contamination source, were processed by ultrafiltration (5000 Da cut-off) and Solid Phase Extraction (SPE) to determine the association of selected artificial radionuclides ((60)Co, (137)Cs) with Natural Organic Matter (NOM). The last two sampling episodes (2008 and 2010) also benefited from fluorescence analysis to determine the major character of the NOM. The fluorescence signals are reported as humic-like, fulvic-like and protein-like, which are used to characterize the different NOM types. The NOM from the clean site comprised mostly fine material, whereas the colloidal content (retained by ultrafiltration) was higher (e.g., 15-40% of the Total Organic Carbon - TOC). Most of the 137Cs was present in the colloidal fraction, whereas (60)Co was found in the filtered fraction. Fluorescence analysis, on the other hand, indicated a contrasting behavior between the clean and contaminated sites, with a dominance of protein-like material, a feature usually associated with human impacts. Finally, SPE removed almost quantitatively the protein-like material (>90%), whereas it removed a much smaller fraction of the (137)Cs (<28%). This finding indicates that the (137)Cs preferential binding occurs with a fraction other than the protein-like NOM, likely the fulvic-like or humic-like portion. PMID:24476752

  2. Modal disorder and phase transition in Rb0.91Nb0.96W1.04O5.98. Interpretation of X-ray diffuse scattering using the group theory approach

    NASA Astrophysics Data System (ADS)

    Komornicka, Dorota; Wołcyrz, Marek; Pietraszko, Adam; Sikora, Wiesława; Majchrowski, Andrzej

    2015-10-01

    A complex scheme of atomic displacements (modes) that break the Fd 3 bar m symmetry of the high-temperature (Tc>395 K) cubic phase of Rb0.91Nb0.96W1.04O5.98 and ultimately lead to a phase transition to the tetragonal phase was determined using the group theory approach. The resulting set of modes was used to construct a model of the disordered crystal that provides diffuse scattering (particularly characteristic extinctions) that is highly consistent with the experimental results. The resulting solution reveals a disordered structure of cubic Rb0.91Nb0.96W1.04O5.98, which is a system of intersecting {111}-type planes in which Nb/W atoms (statistically occupying the centers of oxygen octahedra) are shifted along three symmetry-equivalent <110> directions parallel to these planes. Oxygen atoms also move in a characteristic manner, but their shifts are considerably smaller and do not substantially affect the diffuse scattering pattern. The movements of Rb atoms are large but uncorrelated. The obtained picture of the local structure of cubic Rb0.91Nb0.96W1.04O5.98 makes it necessary to change the interpretation of existing physical measurements, particularly dielectric measurements. Furthermore, the determined structure of the low-temperature tetragonal phase that exists below 395 K was found to be non-polar (space group I 4 bar2d). Group theory analysis provides a coherent picture of the phase transition from the disordered cubic phase to the ordered tetragonal phase. At Tc, in a multimodal crystal of the high-temperature phase, mode symmetry breaking occurs, and each of the four displacive modes is decomposed: only 1/4 of the atoms of every mode of k=(x,x,x) retain their <110>-type in-plane displacements; the displacements of the remaining atoms undergo reorientation to fulfill the conditions imposed by the k=(0,0,0) mode. The former group of displacements defines the direction of the appearing tetragonal axis.

  3. The Natural Enrichment of Stable Cesium in Weathered Micaceous Materials and Its Implications for 137Cs Sorption.

    SciTech Connect

    ELLIOTT, W CRAWFORD; KAHN, BERND; ROSSON, ROBERT; WAMPLER, J MARION; ROSE, SETH E; KROGSTAD, EIRIK J; KAPLAN, DANIEL; ZAUNBRECHER, LAURA

    2011-11-14

    In this exploratory project, we are testing two interrelated hypotheses about the sorption of Cs within weathered micaceous materials in subsurface regolith materials from the Savannah River Site (SRS) located on the Atlantic Coastal Plain: 1) that stable cesium has become significantly enriched relative to potassium in subsurface micaceous particles as a result of chemical weathering processes; and 2) that the Cs so present is sufficient to be a major factor determining the ability of the subsurface materials to take up and hold 137Cs. To test these hypotheses, we collected by hand augur soil samples corresponding to soils representative at the SRS: upland regolith (Fuquay series); soils formed on Tobacco Road Sandstone; and, soils formed on Quaternary Alluvium. From our data, the quantification of the amounts of stable cesium concentrated in various sites within 2:1 phyllosilicates by natural processes is highly relevant toward understanding the future sorption of 137Cs by the mica, illite, vermiculite, and hydroxyl interstratified vermiculite (HIV) phases present in the subsurface at and in proximity to SRS. Studying sorption and fixation of Cs in these micaceous phases interlayers potentially leads to increased knowledge to the extent that stable Cs resists exchange with ion exchange cations (Mg, NH4, or even alkyl ammonium compounds) and to the extent that Cs can become fixed over the long term. Such knowledge will help in the development of 137Cs remediation strategies for the long-term, which is a critical aspect of the SBR goals. We characterized the mineralogy, K-Ar ages of the soil and soil clay fractions (before and after acid treatment), and alkali element chemistry (K, Rb, Cs) of the clay fractions of soils collected from these three different types of soils. The clay fractions of the Fuquay soils are composed of kaolinite, and hydroxy interstratified vermiculite (HIV). Kaolinite, HIV, quartz, gibbsite and illite are found in the quaternary soils

  4. Compressibility and pressure-induced disorder in superconducting phase-separated Cs0.72Fe1.57Se2

    NASA Astrophysics Data System (ADS)

    Svitlyk, V.; Chernyshov, D.; Bosak, A.; Pomjakushina, E.; Krzton-Maziopa, A.; Conder, K.; Pomjakushin, V.; Dmitriev, V.; Garbarino, G.; Mezouar, M.

    2014-04-01

    The pressure-dependent diffraction response of the superconducting phase-separated Cs0.72Fe1.57Se2(Tc = 28.5 K) has been studied at room temperature using synchrotron radiation up to the pressure of 19 GPa. The main and secondary phases of Cs0.72Fe1.57Se2 have been observed in the whole pressure range. The main ordered phase has been found to undergo an order-disorder transition in the Fe sublattice at P = 11 GPa with the corresponding kinetics on the order of hours. Contrary to the analogous temperature-induced transition, the secondary phase has not been suppressed suggesting that its stability pressure range is higher than 19 GPa or the corresponding transformation kinetics is too slow at room temperature. Together with the previously reported pressure-dependent resistivity and magnetic susceptibility measurements, this work indicates that superconductivity in the AxFe2-ySe2 (A: alkali metals) phases could be related to the Fe-vacancy ordering in the main phase.

  5. First-principles study of the binary intermetallics in the Au-Rb system

    NASA Astrophysics Data System (ADS)

    Benmechri, Achraf; Djaballah, Yassine; Amer, Ahmed Said; Belgacem-Bouzida, Aissa; Bouderba, Hichem

    2014-06-01

    First-principles calculations within density functional theory (DFT) with the projector augmented wave (PAW) technique were used to investigate the stabilities of intermetallics in the Au-Rb system at 0 K. Four intermetallics: Au7Rb3, Au3Rb2, Au5Rb and AuRb were investigated in their observed experimental structures. The Au2Rb compound, reported in the Au-Rb phase diagrams without specifying explicitly its structure, was also investigated by inspecting several hypothetical structures. A suspect compound (AuRb2) was also investigated. Results show that: (i) The Au3Rb2 and Au7Rb3 compounds, which were never reported in any Au-Rb phase diagram, are stable at 0 K. (ii) The Au2Rb compound is not a ground state for all the tested structures. (iii) Stability of the Au5Rb and AuRb compounds was confirmed. (iv) The new compound AuRb2, not yet reported experimentally, is found mechanically stable at 0 K.

  6. Thermal behavior in the magnetic phase diagram of the easy axis antiferromagnet Cs2FeCl5·H2O

    NASA Astrophysics Data System (ADS)

    Freitas, R. S.; Paduan-Filho, A.; Becerra, C. C.

    2016-03-01

    The specific heat at a constant applied field C H(T) and at fixed temperatures C T(H) of single crystals of the low anisotropy antiferromagnet Cs2FeCl5·H2O was measured across the different boundaries of its magnetic phase diagram, in magnetic fields up to 9 T applied parallel and perpendicular to the easy axis direction and to temperatures down to 0.3 K. The specific heat data indicate that the critical behavior along the antiferromagnetic to paramagnetic phase boundary and the spin-flop to paramagnetic phase boundary, are basically the same. We also measured the specific heat when the first order antiferromagnetic to spin-flop phase boundary is crossed at a fixed temperature. The entropy of the different magnetic phases is discussed.

  7. Ferroelectric properties of RbNbO3 and RbTaO3

    NASA Astrophysics Data System (ADS)

    Lebedev, A. I.

    2015-02-01

    Phonon spectra of cubic rubidium niobate and rubidium tantalate with the perovskite structure are calculated from first principles within the density functional theory. Based on the analysis of unstable modes in phonon spectra, symmetries of possible distorted phases are determined, their energies are calculated, and it is shown that R3 m is the ground-state structure of RbNbO3. In RbTaO3, the ferroelectric instability is suppressed by zero-point lattice vibrations. For ferroelectric phases of RbNbO3, spontaneous polarization, piezoelectric, nonlinear optical, electro-optical, and other properties as well as the energy band gap in the LDA and GW approximations are calculated. The properties of rhombohedral RbNbO3 are compared with those of rhombohedral KNbO3, LiNbO3, and BaTiO3.

  8. From {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} to {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} infinite chains in A{sub 6}U{sub 2}Mo{sub 4}O{sub 21} (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure of Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})

    SciTech Connect

    Yagoubi, S.; Obbade, S.; Saad, S.; Abraham, F.

    2011-05-15

    A new caesium uranyl molybdate belonging to the M{sub 6}U{sub 2}Mo{sub 4}O{sub 21} family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A{sub 6}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}], the caesium compound Cs{sub 6}U{sub 2}Mo{sub 4}O{sub 21} should be written Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] crystallizes in the triclinic symmetry with space group P1-bar and a=10.4275(14) A, b=15.075(2) A, c=17.806(2) A, {alpha}=70.72(1){sup o}, {beta}=80.38(1){sup o} and {gamma}=86.39(1){sup o}, V=2604.7(6) A{sup 3}, Z=4, {rho}{sub mes}=5.02(2) g/cm{sup 3} and {rho}{sub cal}=5.08(3) g/cm{sup 3}. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R{sub 1}=0.0464 and wR{sub 2}=0.0950 for 596 parameters with 6964 independent reflections with I{>=}2{sigma}(I) collected on a BRUKER AXS diffractometer with Mo(K{alpha}) radiation and a CCD detector. The crystal structure of Cs compound is characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} parallels chains built from U{sub 2}O{sub 13} dimeric units, MoO{sub 4} tetrahedra and MoO{sub 5} square pyramids, whereas, Na, K and Rb compounds are characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} parallel chains formulated simply of U{sub 2}O{sub 13} units and MoO{sub 4} tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 610 {sup o

  9. Low temperature structural modification in Rb2ZrF6: Investigations by perturbed angular correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Dey, S. K.; Dey, C. C.; Saha, S.

    2016-06-01

    Temperature dependent perturbed angular correlation (PAC) measurements in crystalline compounds Rb2ZrF6 and Cs2HfF6 have been performed in the temperature range 298-753 K. In Rb2ZrF6, four discrete quadrupole interaction frequencies have been observed at room temperature which correspond to four minor structural modifications. From previous measurements, on the other hand, two structural modifications of this compound were known. A displacive phase transition, probably, occurs at low temperature due to rotation of the ZrF62- octahedron and produces different structural modifications. From present measurements in Rb2ZrF6, two quadrupole interaction frequencies [ωQ=26.1(3) Mrad/s, η=0.55(2), δ=5(1)% and ωQ=148.7(3) Mrad/s, η=0.538(5), δ=1.2%] have been found at room temperature which were not found from previous studies. In Cs2HfF6, these new structural modifications have not been observed.

  10. Cs3ScCl6

    PubMed Central

    Ward, Matthew D.; Ibers, James A.

    2014-01-01

    Crystals of tricaesium scandium(III) hexa­chloride were obtained as a side product from the reaction of U, SnCl2, Sc, and S in a CsCl flux at 1073 K. Cs3ScCl6 crystallizes in the Rb3YCl6 structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl6]3− octa­hedra that are surrounded by Cs+ cations. Two Cs+ cations have inter­actions with eight Cl− anions, while the third has inter­actions with ten Cl− anions. PMID:24940185

  11. Cs3ScCl6.

    PubMed

    Ward, Matthew D; Ibers, James A

    2014-06-01

    Crystals of tricaesium scandium(III) hexa-chloride were obtained as a side product from the reaction of U, SnCl2, Sc, and S in a CsCl flux at 1073 K. Cs3ScCl6 crystallizes in the Rb3YCl6 structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl6](3-) octa-hedra that are surrounded by Cs(+) cations. Two Cs(+) cations have inter-actions with eight Cl(-) anions, while the third has inter-actions with ten Cl(-) anions. PMID:24940185

  12. Effects of Hyperfine Mixing of Rydberg-ground molecular potentials in Rb

    NASA Astrophysics Data System (ADS)

    Maclennan, Jamie; Ramos, Andira; Thaicharoen, Nithiwadee; Raithel, Georg

    2016-05-01

    Rydberg molecules formed by the scattering between a ground-state atom and a Rydberg electron can offer new insight into the nature of atomic interactions and molecular structure. Shallow bound states that arise from hyperfine-induced mixing of singlet and triplet channels have recently been predicted and observed for P-states in Cs and S-states in 87 Rb. Here we present progress toward characterizing Rb (nD + 5 S1/2) molecules, including a comparison of the hyperfine-mixing effects between the two isotopes (85 Rb and 87 Rb).

  13. The happy marriage between electron-phonon superconductivity and Mott physics in Cs3C60: A first-principle phase diagram

    NASA Astrophysics Data System (ADS)

    Capone, Massimo; Nomura, Yusuke; Sakai, Shiro; Giovannetti, Gianluca; Arita, Ryotaro

    The phase diagram of doped fullerides like Cs3C60 as a function of the spacing between fullerene molecules is characterized by a first-order transition between a Mott insulator and an s-wave superconductor with a dome-shaped behavior of the critical temperature. By means of an ab-initio modeling of the bandstructure, the electron-phonon interaction and the interaction parameter and a Dynamical Mean-Field Theory solution, we reproduce the phase diagram and demonstrate that phonon superconductivity benefits from strong correlations confirming earlier model predictions. The role of correlations is manifest also in infrared measurements carried out by L. Baldassarre. The superconducting phase shares many similarities with ''exotic'' superconductors with electronic pairing, suggesting that the anomalies in the ''normal'' state, rather than the pairing glue, can be the real common element unifying a wide family of strongly correlated superconductors including cuprates and iron superconductors

  14. Cyclin-dependent kinase 4 may be expressed as multiple proteins and have functions that are independent of binding to CCND and RB and occur at the S and G2/M phases of the cell cycle

    PubMed Central

    Sun, Yuan; Lou, Xiaomin; Yang, Min; Yuan, Chengfu; Ma, Ling; Xie, Bing-Kun; Wu, Jian-min; Yang, Wei; Shen, Steven XJ; Xu, Ningzhi; Liao, D Joshua

    2013-01-01

    Cyclin-dependent kinase 4 (CDK4) is known to be a 33 kD protein that drives G1 phase progression of the cell cycle by binding to a CCND protein to phosphorylate RB proteins. Using different CDK4 antibodies in western blot, we detected 2 groups of proteins around 40 and 33 kD, respectively, in human and mouse cells; each group often appeared as a duplet or triplet of bands. Some CDK4 shRNAs could decrease the 33 kD wild-type (wt) CDK4 but increase some 40 kD proteins, whereas some other shRNAs had the opposite effects. Liquid chromatography–mass spectrometry/mass spectrometry analysis confirmed the existence of CDK4 isoforms smaller than 33 kD but failed to identify CDK4 at 40 kD. We cloned one CDK4 mRNA variant that lacks exon 2 and encodes a 26 kD protein without the first 74 amino acids of the wt CDK4, thus lacking the ATP binding sequence and the PISTVRE domain required for binding to CCND. Co-IP assay confirmed that this ΔE2 protein lost CCND1- and RB1-binding ability. Moreover, we found, surprisingly, that the wt CDK4 and the ΔE2 could inhibit G1–S progression, accelerate S–G2/M progression, and enhance or delay apoptosis in a cell line-specific manner in a situation where the cells were treated with a CDK4 inhibitor or the cells were serum-starved and then replenished. Hence, CDK4 seems to be expressed as multiple proteins that react differently to different CDK4 antibodies, respond differently to different shRNAs, and, in some situations, have previously unrecognized functions at the S–G2/M phases of the cell cycle via mechanisms independent of binding to CCND and RB. PMID:24091631

  15. New hypodiphosphates of the alkali metals: Synthesis, crystal structure and vibrational spectra of the hypodiphosphates(IV) M{sub 2}[(H{sub 2}P{sub 2}O{sub 6})(H{sub 4}P{sub 2}O{sub 6})] (M=Rb and Cs)

    SciTech Connect

    Wu, Peng; Wiegand, Thomas; Eckert, Hellmut

    2012-10-15

    The new hypodiphosphates(IV) Rb{sub 2}[(H{sub 2}P{sub 2}O{sub 6})(H{sub 4}P{sub 2}O{sub 6})] (1) and Cs{sub 2}[(H{sub 2}P{sub 2}O{sub 6})(H{sub 4}P{sub 2}O{sub 6})] (2) were synthesized by soft chemistry reactions from aqueous solutions of hypophosphoric acid and the corresponding heavy alkali-metal carbonates. Their crystal structures were determined by single crystal X-ray diffraction. Both compounds crystallize isotypic in the triclinic space group P-1 with one formula unit in the unit cell. The structures are built up by discrete (H{sub 2}P{sub 2}O{sub 6}){sup 2-} and (H{sub 4}P{sub 2}O{sub 6}) units in staggered conformation for the P{sub 2}O{sub 6} skeleton and the corresponding alkali-metal cations. In the (H{sub 2}P{sub 2}O{sub 6}){sup 2-} ion the hydrogen atoms are in a 'trans-trans' conformation. O{center_dot}H-O hydrogen bonds between the (H{sub 2}P{sub 2}O{sub 6}){sup 2-} and (H{sub 4}P{sub 2}O{sub 6}) groups consolidate the structures into a three-dimensional network. The FT-Raman and {sup 31}P and {sup 1}H and MAS NMR spectra of the title compounds have been recorded and interpreted, especially with respect to their assignment to the (H{sub 2}P{sub 2}O{sub 6}){sup 2-} and (H{sub 4}P{sub 2}O{sub 6}) groups. Thermogravimetric data of 2 have been interpreted in terms of a thermal decomposition model. - Graphical Abstract: The layered compounds Rb{sub 2}[(H{sub 2}P{sub 2}O{sub 6})(H{sub 4}P{sub 2}O{sub 6})] and Cs{sub 2}[(H{sub 2}P{sub 2}O{sub 6})(H{sub 4}P{sub 2}O{sub 6})] have been synthesized and investigated. Both crystallize isotypic. The structures are built up by discrete (H{sub 2}P{sub 2}O{sub 6}){sup 2-} and (H{sub 4}P{sub 2}O{sub 6}) units and the corresponding alkali-metal cations. Highlights: Black-Right-Pointing-Pointer Synthesis and single-crystal structure of new alkali hypodiphosphates. Black-Right-Pointing-Pointer Structures are characterized by [(H{sub 2}P{sub 2}O{sub 6})(H{sub 4}P{sub 2}O{sub 6})]{sup 2-} units and M{sup +} cations

  16. Rb-Sr age of troctolite 76535

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.; Wasserburg, G. J.

    1976-01-01

    Rb-Sr systematics is studied for the lunar troctolite 76535 in phases covering a wide range of Rb and Sr concentrations. A line is obtained corresponding to an age of 4.61 plus or minus 0.07 AE and an initial Sr-87/Sr-86 of 0.69900 plus or minus 0.00003. The Rb-Sr age of 4.55 plus or minus 0.10 AE for the dunite (72417) and that of the troctolite are in approximate agreement and permit an interpretation that these rocks formed during a single major lunar differentiation which presumbly produced an anorthositic-gabbroic lunar crust and layered upper mantle.

  17. Electronic properties and structural phase transition in A4 [M4O4] (A=Li, Na, K and Rb; M=Ag and Cu): A first principles study

    NASA Astrophysics Data System (ADS)

    Umamaheswari, R.; Yogeswari, M.; Kalpana, G.

    2013-02-01

    Self-consistent scalar relativistic band structure calculations for AMO (A=Li, Na, K and Rb; M=Ag and Cu) compounds have been performed using the tight-binding linear muffin-tin orbital (TB-LMTO) method within the local density approximation (LDA). At ambient conditions, these compounds are found to crystallize in tetragonal KAgO-type structure with two different space group I-4m2 and I4/mmm. Nowadays, hypothetical structures are being considered to look for new functional materials. AMO compounds have stoichiometry similar to eight-electron half-Heusler materials of type I-I-VI which crystallizes in cubic (C1b) MgAgAs-type structure with space group F-43m. For all these compounds, by interchanging the positions of atoms in the hypothetical cubic structure, three phases (α, β and γ) are formed. The energy-volume relation for these compounds in tetragonal KAgO-type structure and cubic α, β and γ phases of related structure have been obtained. Under ambient conditions these compounds are more stable in tetragonal KAgO-type (I4/mmm) structure. The total energies calculated within the atomic sphere approximation (ASA) were used to determine the ground state properties such as equilibrium lattice parameters, c/a ratio, bulk modulus, cohesive energy and are compared with the available experimental results. The results of the electronic band structure calculations at ambient condition show that LiCuO and NaMO are indirect band gap semiconductors whereas KMO and RbMO are direct band gap semiconductors. At high pressure the band gap decreases and the phenomenon of band overlap metallization occur. Also these compounds undergo structural phase transition from tetragonal I-4m2 phase to cubic α-phase and transition pressures were calculated.

  18. Flux Synthesis, Structure, Properties, and Theoretical Magnetic Study of Uranium(IV)-Containing A2USi6O15 (A = K, Rb) with an Intriguing Green-to-Purple, Crystal-to-Crystal Structural Transition in the K Analogue.

    PubMed

    Morrison, Gregory; Ramanantoanina, Harry; Urland, Werner; Smith, Mark D; zur Loye, Hans-Conrad

    2015-06-01

    The flux growth of uranium(IV) oxides presents several challenges, and to the best of our knowledge, only one example has ever been reported. We succeeded in growing two new reduced uranium silicates A2USi6O15 (A = K, Rb) under flux growth conditions in sealed copper tubes. The compounds crystallize in a new structure type with space group C2/c and lattice parameters a = 24.2554(8) Å, b = 7.0916(2) Å, c = 17.0588(6) Å, β = 97.0860(6) ° (K) and a = 24.3902(8) Å, b = 7.1650(2) Å, c = 17.2715(6) Å, β = 96.8600(6) ° (Rb). A2USi6O15 (A = K, Rb) are isocompositional to a previously reported Cs2USi6O15, and the two structures are compared. K2USi6O15 undergoes an interesting crystal-to-crystal structural phase transition at T ≈ 225 K to a triclinic structure, which is accompanied by an intense color change. The magnetic properties of A2USi6O15 (A = K, Rb, Cs) are reported and differ from the magnetism observed in other U(4+) compounds. Calculations are performed on the (UO6)(-8) clusters of K2USi6O15 to study the cause of these unique magnetic properties. PMID:25978501

  19. High-Temperature Phase Transitions in CsH2PO4 Under Ambient and High-Pressure Conditions: A Synchrotron X-ray Diffraction Study

    SciTech Connect

    Botez,C.; Hermosillo, J.; Zhang, J.; Qian, J.; Zhao, Y.; Majzlan, J.; Chianelli, R.; Pantea, C.

    2007-01-01

    To clarify the microscopic origin of the temperature-induced three-order-of-magnitude jump in the proton conductivity of CsH2PO4 (superprotonic behavior), we have investigated its crystal structure modifications within the 25-300 C temperature range under both ambient- and high-pressure conditions using synchrotron x-ray diffraction. Our high-pressure data show no indication of the thermal decomposition/polymerization at the crystal surface recently proposed as the origin of the enhanced proton conductivity. Instead, we found direct evidence that the superprotonic behavior of the title material is associated with a polymorphic structural transition to a high-temperature cubic phase. Our results are in excellent agreement with previous high-pressure ac impedance measurements.

  20. Positive nonlinear pressure shift of Cs in Ne

    NASA Astrophysics Data System (ADS)

    Xia, Tian; McGuyer, Bart; Jau, Yuan-Yu; Happer, William

    2010-03-01

    We demonstrate that the hyperfine resonance frequency of ground state Cs atoms have a nonlinear dependence on the pressure of the buffer gas Ne at a fixed temperature. The hyperfine resonance frequency of alkali-metal atoms is shifted by an amount, which had long been assumed to be linear with the buffer gas pressure until Fei Gong discovered that the shift of Rb and Cs hyperfine resonance frequency has a nonlinear dependence on the pressure of the buffer gas Ar and Kr. While the nonlinear pressure shift of Cs in Ar and Kr is negative, we found that the nonlinear pressure shift of Cs hyperfine frequency in Ne is positive. The reason of the nonlinear shift is the three body collision(eg: Cs-Ne-Ne) and the formation of Van der Waals molecules of a Cs atom and a buffer gas atom of Ar, Kr, or Ne. The hyperfine precession rate of a Cs atom bound in molecule has a shift respect to a free Cs atom. The reversal sign of this nonlinear pressure shift of Cs in Ne respect to Ar and Kr demonstrate that the shift of the hyperfine precession rate of Cs in CsNe is reversed respect to CsAr and CsKr.

  1. Phase transitions and equation of state of CsI under high pressure and the development of a focusing system for x-rays

    SciTech Connect

    Wu, Yan.

    1990-11-01

    The phase transitions and equation of state of ionic solid cesium iodide were studied under high pressure and room temperature in a diamond anvil cell. The studies were carried out using both energy dispersive and angular dispersive diffraction methods on synchrotron radiation sources over the pressure range from atmospheric pressure to over 300 gigapascals (3 million atmospheres). CsI undergoes a distinct phase transition at about 40 GPa, a pressure that is much lower than the reported insulator-metal transition at 110 GPa, from the atmospheric pressure B2(CsCl) structure to an orthorhombic structure. At higher pressures, a continuous distortion in the structure was observed with a final structure similar to a hcp lattice under ultra high pressure. No volume discontinuity was observed at the insulator-metal transition. The newly found transition sequence is different from the result of previous static compression studies. The current structure has a smaller unit cell volume than the previous assignment. This has resolved a long existing controversy among the previous static compression studies, the dynamic compression studies, and the theoretical studies. The current results also explain the apparent discrepancy between the present study and the previous static studies. We also present the development of a focusing system for high energy x-rays (> 12 keV) that is particularly suited for high pressure diffraction studies. This system uses a pair of multilayer coated spherical mirrors in a Kirkpatrick-Baez geometry. A focused beam size less than 10 micron in diameter can be readily achieved with sufficient intensity to perform diffraction studies. 93 refs., 46 figs., 15 tabs.

  2. Defining a new vision for the retinoblastoma gene: report from the 3rd International Rb Meeting

    PubMed Central

    2013-01-01

    The retinoblastoma tumor suppressor (Rb) pathway is mutated in most, if not all human tumors. In the G0/G1 phase, Rb and its family members p107 and p130 inhibit the E2F family of transcription factors. In response to mitogenic signals, Cyclin-dependent kinases (CDKs) phosphorylate Rb family members, which results in the disruption of complexes between Rb and E2F family members and in the transcription of genes essential for S phase progression. Beyond this role in early cell cycle decisions, Rb family members regulate DNA replication and mitosis, chromatin structure, metabolism, cellular differentiation, and cell death. While the RB pathway has been extensively studied in the past three decades, new investigations continue to provide novel insights into basic mechanisms of cancer development and, beyond cancer, help better understand fundamental cellular processes, from plants to mammals. This meeting report summarizes research presented at the recently held 3rd International Rb Meeting. PMID:24257515

  3. Defining a new vision for the retinoblastoma gene: report from the 3rd International Rb Meeting.

    PubMed

    Rubin, Seth M; Sage, Julien

    2013-01-01

    The retinoblastoma tumor suppressor (Rb) pathway is mutated in most, if not all human tumors. In the G0/G1 phase, Rb and its family members p107 and p130 inhibit the E2F family of transcription factors. In response to mitogenic signals, Cyclin-dependent kinases (CDKs) phosphorylate Rb family members, which results in the disruption of complexes between Rb and E2F family members and in the transcription of genes essential for S phase progression. Beyond this role in early cell cycle decisions, Rb family members regulate DNA replication and mitosis, chromatin structure, metabolism, cellular differentiation, and cell death. While the RB pathway has been extensively studied in the past three decades, new investigations continue to provide novel insights into basic mechanisms of cancer development and, beyond cancer, help better understand fundamental cellular processes, from plants to mammals. This meeting report summarizes research presented at the recently held 3rd International Rb Meeting. PMID:24257515

  4. Comment on "Does the structural superionic phase transition at 231 °C in CsH2PO4 really not exist?" [J. Chem. Phys. 110, 4847 (1999)

    NASA Astrophysics Data System (ADS)

    Bronowska, Wieslawa

    2001-01-01

    Single crystal and powder diffraction investigations have revealed that the paraelectric phase of cesium dihydrogen phosphate, CsH2PO4 (CDP), from the crystallographic point of view is stable (space group P21/m) up to ca. 231 °C. At this temperature a structural phase transition from the paraelectric phase to the superionic phase (space group Pm-3m) has been observed. The superionic phase of CDP is unstable under normal air condition due to dehydration process. Under H2O-saturated atmosphere the superionic phase transition of CDP takes place without decomposition and is reversible with a temperature hysteresis on cooling.

  5. Phase Behavior of Complex Superprotonic Solid Acids

    NASA Astrophysics Data System (ADS)

    Panithipongwut, Chatr

    Superprotonic phase transitions and thermal behaviors of three complex solid acid systems are presented, namely Rb3H(SO4) 2-RbHSO4 system, Rb3H(SeO4)2-Cs 3H(SeO4)2 solid solution system, and Cs6 (H2SO4)3(H1.5PO4) 4. These material systems present a rich set of phase transition characteristics that set them apart from other, simpler solid acids. A.C. impedance spectroscopy, high-temperature X-ray powder diffraction, and thermal analysis, as well as other characterization techniques, were employed to investigate the phase behavior of these systems. Rb3H(SO4)2 is an atypical member of the M3H(XO4)2 class of compounds (M = alkali metal or NH4+ and X = S or Se) in that a transition to a high-conductivity state involves disproportionation into two phases rather than a simple polymorphic transition [1]. In the present work, investigations of the Rb3H(SO4)2-RbHSO4 system have revealed the disproportionation products to be Rb2SO 4 and the previously unknown compound Rb5H3(SO 4)4. The new compound becomes stable at a temperature between 25 and 140 °C and is isostructural to a recently reported trigonal phase with space group P3m of Cs5H 3(SO4)4 [2]. At 185 °C the compound undergoes an apparently polymorphic transformation with a heat of transition of 23.8 kJ/mol and a slight additional increase in conductivity. The compounds Rb3H(SeO4)2 and Cs 3H(SeO4)2, though not isomorphous at ambient temperatures, are quintessential examples of superprotonic materials. Both adopt monoclinic structures at ambient temperatures and ultimately transform to a trigonal (R3m) superprotonic structure at slightly elevated temperatures, 178 and 183 °C, respectively. The compounds are completely miscible above the superprotonic transition and show extensive solubility below it. Beyond a careful determination of the phase boundaries, we find a remarkable 40-fold increase in the superprotonic conductivity in intermediate compositions rich in Rb as compared to either end-member. The compound Cs6(H2

  6. Rb binds c-Jun and activates transcription.

    PubMed Central

    Nead, M A; Baglia, L A; Antinore, M J; Ludlow, J W; McCance, D J

    1998-01-01

    The retinoblastoma protein (Rb) acts as a critical cell-cycle regulator and loss of Rb function is associated with a variety of human cancer types. Here we report that Rb binds to members of the AP-1 family of transcription factors, including c-Jun, and stimulates c-Jun transcriptional activity from an AP-1 consensus sequence. The interaction involves the leucine zipper region of c-Jun and the B pocket of Rb as well as a C-terminal domain. We also present evidence that the complexes are found in terminally differentiating keratinocytes and cells entering the G1 phase of the cell cycle after release from serum starvation. The human papillomavirus type 16 E7 protein, which binds to both c-Jun and Rb, inhibits the ability of Rb to activate c-Jun. The results provide evidence of a role for Rb as a transcriptional activator in early G1 and as a potential modulator of c-Jun expression during keratinocyte differentiation. PMID:9545246

  7. High-pressure phase transitions in rubidium and caesium hydroxides.

    PubMed

    Hermann, Andreas

    2016-06-28

    A computational investigation of the high-pressure phase sequence of the heaviest alkali hydroxides, RbOH and CsOH, shows that the phase diagram of both compounds is richer than hitherto thought. First-principles calculations suggest, based on energetics and comparisons to experimental diffraction and spectroscopy signatures, that the high-pressure phase RbOH-VI, stable above 6 GPa in experiment, should be assigned the KOH-VI structure type, and features localised hydrogen-bonded (OH)4 units. Meanwhile, a new high-pressure phase CsOH-VII is predicted to be stable above 10 GPa in an isosymmetric phase transition that, like RbOH-VI, marks the transition from layered to three-dimensional network structures under increased compression. Both new phases highlight an unexpected flexibility of hydrogen bond network formation in a series of compounds that seemingly only vary in the cation size, and potential consequences for similar systems, such as water-carrying minerals, are discussed briefly. PMID:27271485

  8. High-pressure behaviour of Cs2V3O8 fresnoite

    NASA Astrophysics Data System (ADS)

    Grzechnik, Andrzej; Yeon, Jeongho; Zur Loye, Hans-Conrad; Friese, Karen

    2016-06-01

    Crystal structure of Cs2V3O8 fresnoite (P4bm, Z=2) has been studied using single-crystal X-ray diffraction in a diamond anvil cell to 8.6 GPa at room temperature. Cs2V3O8 undergoes a reversible first-order phase transition at about 4 GPa associated with anomalies in the pressure dependencies of the lattice parameters and unit-cell volume but without any symmetry change. Both structures consist of layers of corner-sharing V5+O4 tetrahedra and V4+O5 tetragonal pyramids separated by the Cs+ cations located between the layers. At low pressures, the compression has little effect on the polarity of the structure. Above 4 GPa, the pseudosymmetry with respect to the corresponding centrosymmetric space group P4/mbm abruptly increases. The effects of external pressure and of the A+ cation substitution in the vanadate fresnoites A2V3O8 (A+: K+, Rb+, NH4+, Cs+) are discussed.

  9. Cdk5-mediated inhibition of APC/C-Cdh1 switches on the cyclin D1-Cdk4-pRb pathway causing aberrant S-phase entry of postmitotic neurons

    PubMed Central

    Veas-Pérez de Tudela, Miguel; Maestre, Carolina; Delgado-Esteban, María; Bolaños, Juan P.; Almeida, Angeles

    2015-01-01

    The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase that regulates cell cycle progression in proliferating cells. To enter the S-phase, APC/C must be inactivated by phosphorylation of its cofactor, Cdh1. In post-mitotic cells such as neurons APC/C-Cdh1 complex is highly active and responsible for the continuous degradation of mitotic cyclins. However, the specific molecular pathway that determines neuronal cell cycle blockade in post-mitotic neurons is unknown. Here, we show that activation of glutamatergic receptors in rat cortical primary neurons endogenously triggers cyclin-dependent kinase-5 (Cdk5)-mediated phosphorylation of Cdh1 leading to its cytoplasmic accumulation and disassembly from the APC3 core protein, causing APC/C inactivation. Conversely, pharmacological or genetic inhibition of Cdk5 promotes Cdh1 ubiquitination and proteasomal degradation. Furthermore, we show that Cdk5-mediated phosphorylation and inactivation of Cdh1 leads to p27 depletion, which switches on the cyclin D1-cyclin-dependent kinase-4 (Cdk4)-retinoblastoma protein (pRb) pathway to allow the S-phase entry of neurons. However, neurons do not proceed through the cell cycle and die by apoptosis. These results indicate that APC/C-Cdh1 actively suppresses an aberrant cell cycle entry and death of neurons, highlighting its critical function in neuroprotection. PMID:26658992

  10. [Prognosis of dynamics and risk of exceeding permissible levels of 137Cs and 90Sr contents in fish in the Kiev Reservoir at the late phase of the Chernobyl accident].

    PubMed

    Homutinin, Iu V; Kashparov, V A; Kuz'menko, A V; Pavliuchenko, V V

    2013-01-01

    On the basis of the radionuclide specific activity measurements made on 832 samples of fish in 2009-2011 and taking into account literature data, the parameters of the stochastic model have been derived to describe the 137Cs and 90Sr contents in typical commercial fish species in the Kiev Reservoir at the late phase of the Chernobyl accident, including: statistical variability, seasonal changes and monotonous long-term trends. At any fixed moment of the year the standard deviations of logarithms of the 137Cs and 90Sr specific activities in carnivorous and benthophage fish species do not reliably differ, making up at average 0.4. The maximum vari- ation of the 137Cs specific activity (a four-fold decrease from April to November) was observed in pike. The obtained values of the ecological half-life periods for 137Cs and 90Sr (1.3-14 years) in fish of the Kiev reservoir in 2002-2012 were significantly lower than both the radioactive decay periods and the estimates of the IAEA Chernobyl Forum. Based on the obtained model parameters, the dynamics of the 137Cs and 90Sr specific ac- tivities in main commercial fish of the Kiev reservoir has been described and the risk of exceeding the permis- sible levels of these radionuclides in fish at the late phase of the Chernobyl accident has been estimated. Now the risk of catching fish with the specific activities of 137Cs and 90Sr above the permissible levels (150 Bq/kg and 35 Bq/kg, respectively) does not exceed 10% (except perch in the spring spawning period that is banned for fishing in Ukraine). Corresponding risks for roach, white bream and rudd are less than 0.1%. PMID:25427374

  11. [Prognosis of dynamics and risk of exceeding permissible levels of 137Cs and 90Sr contents in fish in the Kiev Reservoir at the late phase of the Chernobyl accident].

    PubMed

    2013-01-01

    On the basis of the radionuclide specific activity measurements made on 832 samples of fish in 2009-2011 and taking into account literature data, the parameters of the stochastic model have been derived to describe the 137Cs and 90Sr contents in typical commercial fish species in the Kiev Reservoir at the late phase of the Chernobyl accident, including: statistical variability, seasonal changes and monotonous long-term trends. At any fixed moment of the year the standard deviations of logarithms of the 137Cs and 90Sr specific activities in carnivorous and benthophage fish species do not reliably differ, making up at average 0.4. The maximum vari- ation of the 137Cs specific activity (a four-fold decrease from April to November) was observed in pike. The obtained values of the ecological half-life periods for 137Cs and 90Sr (1.3-14 years) in fish of the Kiev reservoir in 2002-2012 were significantly lower than both the radioactive decay periods and the estimates of the IAEA Chernobyl Forum. Based on the obtained model parameters, the dynamics of the 137Cs and 90Sr specific ac- tivities in main commercial fish of the Kiev reservoir has been described and the risk of exceeding the permis- sible levels of these radionuclides in fish at the late phase of the Chernobyl accident has been estimated. Now the risk of catching fish with the specific activities of 137Cs and 90Sr above the permissible levels (150 Bq/kg and 35 Bq/kg, respectively) does not exceed 10% (except perch in the spring spawning period that is banned for fishing in Ukraine). Corresponding risks for roach, white bream and rudd are less than 0.1%. PMID:25507624

  12. Developments towards detection of 135Cs at VERA

    NASA Astrophysics Data System (ADS)

    Lachner, Johannes; Kasberger, Magdalena; Martschini, Martin; Priller, Alfred; Steier, Peter; Golser, Robin

    2015-10-01

    Radioisotopes produced in natural or anthropogenic fission are widely used for tracer studies of environmental processes, in nuclear forensics, and are important for nuclear waste disposal. Besides the well-known 137Cs, the longer-lived sister isotope 135Cs (T1/2 = 2.3 Myr) is also produced, and the combined measurement of the two isotopes would allow for assessment of contaminating sources. The insufficient suppression of the stable isobar 135Ba presently prevents AMS measurements down to expected natural levels of 135Cs/133Cs ≈ 10-11. Via the difference in electron affinities between Cs and Ba further isobar suppression should be achievable after the installation of the Ion-Laser-Interaction System (ILIAS) at VERA. We present a preparatory study on the performance of the 3 MV VERA AMS facility for 135Cs concerning ion formation, transmission and detection. Since the usual Cs sputtering would obscure the 135Cs/133Cs ratio of a sample, Rb sputtering was successfully applied and tested also for various other typical AMS elements. Partial suppression of 135Ba is possible with the extraction of Cs- and negative Cs-fluorides. Cs- currents of several 10 nA were extracted over hours from mg amounts of Cs2SO4 material. The transmission to various charge states was tested with gas (Ar, He) and foil stripping. Experiments showed that no suppression in the detection system is possible at high beam energies with the VERA facility. For this reason, gas stripping to low charge states (2+, 3+) with transmissions up to 30% is favorable to guarantee optimal beam transport to the detector. In the present setup, utilizing a simple Bragg-type detector, the blank 135Cs/133Cs ratios from chemically pure samples are determined by the 135Ba background to a value of (4.0 ± 1.3)·10-9.

  13. CsSnI[subscript 3]: Semiconductor or Metal? High Electrical Conductivity and Strong Near-Infrared Photoluminescence from a Single Material. High Hole Mobility and Phase-Transitions

    SciTech Connect

    Chung, In; Song, Jung-Hwan; Im, Jino; Androulakis, John; Malliakas, Christos D.; Li, Hao; Freeman, Arthur J.; Kenney, John T.; Kanatzidis, Mercouri G.

    2012-10-29

    CsSnI{sub 3} is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI{sub 3} have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI{sub 3}, coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI{sub 3}. The black orthorhombic form of CsSnI{sub 3} demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI{sub 3} indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of {approx} 10{sup 17} cm{sup -3} and a hole mobility of {approx} 585 cm{sup 2} V{sup -1} s{sup -1}. The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from

  14. A conserved arginine near the filter of Kir1.1 controls Rb/K selectivity.

    PubMed

    Sackin, Henry; Nanazashvili, Mikheil; Li, Hui; Palmer, Lawrence G; Walters, D Eric

    2010-01-01

    ROMK (Kir1.1) channels are important for K secretion and recycling in the collecting duct, connecting tubule and thick ascending limb of the mammalian nephron. We have identified a highly conserved Arg in the P loop of the channel near the selectivity filter that controls Rb/K selectivity. Mutation of this Arg to a Tyr (R128Y-Kir1.1b, R147Y-Kir1.1a) increased the macroscopic conductance ratio, G(Rb)/G(K) by 17 ± 3 fold and altered the selectivity sequence from NH(4) > K > Tl > Rb > Cs in wt-Kir1.1 to: Rb > Cs > Tl > NH(4) > K in R128Y, without significant change in the high K/Na permeability ratio of Kir1.1. R128M produced similar, but smaller, increases in Rb, Tl, NH(4) and Cs conductance relative to K. R128Y remained susceptible to block by both external Ba and the honeybee toxin, TPNQ, although R128Y had a reduced affinity for TPNQ, relative to wild-type. The effect of R128Y-Kir1.1b on the G(Rb)/G(K) ratio can be partly explained by a larger single-channel Rb conductance (12.4 ± 0.5 pS) than K conductance (<1.5 pS) in this mutant. The kinetics of R128Y gating at -120 mV with Rb as the permeant ion were similar to those of wt-Kir1.1 conducting Rb, but with a longer open time (129 ms vs. 6 ms for wt) and two closed states (13 ms, 905 ms), resulting in an open probability (Po) of 0.5, compared to a Po of 0.9 for wt-Kir1.1, which had a single closed state of 1 ms at -120 mV. Single-channel R128Y rectification was eliminated in excised, insideout patches with symmetrical Rb solutions. The large increase in the Rb/K conductance ratio, with no change in K/Na permeability or rectification, is consistent with R128Y-Kir1.1b causing a subtle change in the selectivity filter, perhaps by disruption of an intra-subunit salt bridge (R128-E118) near the filter. PMID:20458182

  15. Magnetic dipole bands in {sup 82}Rb, {sup 83}Rb and {sup 84}Rb

    SciTech Connect

    Schwengner, R.; Schnare, H.; Frauendorf, S.; Doenau, F.; Kaeubler, L.; Prade, H.; Grosse, E.; Jungclaus, A.; Lieb, K. P.; Lingk, C.; Skoda, S.; Eberth, J.; De Angelis, G.; Gadea, A.; Farnea, E.; Napoli, D. R.; Ur, C. A.; Lo Bianco, G.

    1998-12-21

    We have studied the isotopes {sup 82}Rb{sub 45}, {sup 83}Rb{sub 46} and {sup 84}Rb{sub 47} to search for magnetic rotation which is predicted in the tilted-axis cranking model for a certain mass region around A=80. Excited states in these nuclei were populated via the reaction {sup 11}B+{sup 76}Ge with E=50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a {gamma}-coincidence experiment using the spectrometer GASP we have found magnetic dipole bands in each studied nuclide. The regular M1 bands observed in the odd-odd nuclei {sup 82}Rb and {sup 84}Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13{sup -}{<=}J{sup {pi}}{<=}16{sup -}. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type {pi}(fp){pi}g{sub 9/2}{sup 2}{nu}g{sub 9/2}. This is the first evidence of magnetic rotation in the A{approx_equal}80 region. In contrast, the M1 sequences in the odd-even nucleus {sup 83}Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.

  16. Superconductivity in the orthorhombic phase of thermoelectric CsPbxBi4-xTe6 with 0.3≤x≤1.0

    NASA Astrophysics Data System (ADS)

    Zhang, R. X.; Yang, H. X.; Tian, H. F.; Chen, G. F.; Wu, S. L.; Wei, L. L.; Li, J. Q.

    2015-12-01

    Experimental measurements clearly reveal the presence of bulk superconductivity in the CsPbxBi4-xTe6 (0.3≤x≤1.0) materials, i.e. the first member of the thermoelectric series of Cs[PbmBi3Te5+m], these materials have the layered orthorhombic structure containing infinite anionic [PbBi3Te6]- slabs separated with Cs+ cations. Temperature dependences of electrical resistivity, magnetic susceptibility, and specific heat have consistently demonstrated that the superconducting transition in Cs0.96Pb0.25Bi3.75Te6.04 occurs at Tc=3.1 K, with a superconducting volume fraction close to 100% at 1.8 K. Structural study using aberration-corrected STEM/TEM reveals a rich variety of microstructural phenomena in correlation with the Pb-ordering and chemical inhomogeneity. The superconducting material Cs0.96Pb0.25Bi3.75Te6.04 with the highest Tc shows a clear ordered structure with a modulation wave vector of q≈a*/2+c*/1.35 on the a-c plane. Our study evidently demonstrates that superconductivity deriving upon doping of narrow-gap semiconductor is a viable approach for exploration of novel superconductors.

  17. Dynamical effects and ergodicity in the dipolar glass phase: evidence from time-domain EPR and phase memory time studies of AsO(4)(4-) in Rb(1-x)(NH(4))(x)H(2)PO(4) (x = 0,0.5,1).

    PubMed

    Sastry, M D; Gustafsson, H; Danilczuk, M; Lund, A

    2006-05-01

    Three-pulse electron spin echo envelope modulation (ESEEM), hyperfine sublevel correlation spectroscopy (HYSCORE) investigations and two-pulse electron spin echo (ESE) measurements of phase memory time T(M), were carried out, in the 20-200 K temperature range, on an AsO(4)(4-) paramagnetic probe stabilized in RbH(2)PO(4) (RDP), NH(4)H(2)PO(4) (ADP), and dipolar glass Rb(0.5)(NH(4))(0.5)H(2)PO(4) (RADP). The results obtained on ADP revealed hyperfine interaction of the probe ion with the (14)N of the ammonium ion, the coupling constant satisfying the condition of 'cancellation' at a field of 480 mT. The ammonium ion was found to be in two different sites in ADP, which became indistinguishable on the formation of dipolar glass RADP. These results were confirmed by HYSCORE spectral measurements. The fast Fourier transform (FFT) spectra of three-pulse ESEEM decays have clearly revealed the interaction with protons in the [Formula: see text] bond both in ADP and RDP; and in RADP with an averaged coupling constant. The phase memory times in RADP exhibited strong temperature dependence and were found to be dependent on the nuclear spin quantum number m(I) of (75)As. The temperature dependence of T(M) exhibited a well-defined maximum around 90 K, coinciding with the temperature of onset of 'freezing' in Rb(0.5)(NH(4))(0.5)H(2)PO(4). This is symptomatic of dynamic fluctuations in the dipolar glass phase, with onset around 150 K, going through a maximum around 90 K and slowing down on further cooling. These results suggest that in RADP, a dynamical mechanism with progressive slowing down below 90 K is operative in the glass formation. This implies that the RADP system, with x = 0.5, exists in an ergodic relaxor (R)-state in the 20-200 K temperature range wherein every fluctuating monodomain can be viewed as statistically representative of the whole sample. PMID:21690780

  18. Thermodynamic Mixing Properties of Rb-K-Na Feldspars and Relevance to Rb-, NH4-, K-, Na-, and Li-Feldspar Thermal Expansion

    NASA Astrophysics Data System (ADS)

    Hovis, G. L.; Morabito, J.; Mott, A.

    2006-12-01

    -feldspar structure is severely stretched. The failure for K-sanidine to take up high amounts of Rb probably is related to this. This may account also for that fact that the volume of disordered Rb feldspar (synthesized via hydrothermal crystallization using the gel technique of Hamilton and Henderson, Mineralogical Magazine, 1968) is actually less than that of rubicline, even though disordering normally increases volume and despite the fact that the enthalpy of Al-Si disorder in Rb feldspar is what one would expect by comparison with those for K- and Na- feldspar. This also accounts for the stability of pollucite plus silica over Cs feldspar in laboratory ion-exchange experiments. We sincerely thank the Earth Sciences Department of Cambridge University, UK, where our high-T X-ray measurements on feldspars and feldspathoids were conducted. We are grateful to Andrey Kovalskii for helpful advice on the ion-exchange synthesis of Rb-K feldspars.

  19. Do CS-US Pairings Actually Matter? A Within-Subject Comparison of Instructed Fear Conditioning with and without Actual CS-US Pairings

    PubMed Central

    Raes, An K.; De Houwer, Jan; De Schryver, Maarten; Brass, Marcel; Kalisch, Raffael

    2014-01-01

    Previous research showed that instructions about CS-US pairings can lead to fear of the CS even when the pairings are never presented. In the present study, we examined whether the experience of CS-US pairings adds to the effect of instructions by comparing instructed conditioning with and without actual CS-US pairings in a within-subject design. Thirty-two participants saw three fractals as CSs (CS+1, CS+2, CS−) and received electric shocks as USs. Before the start of a so-called training phase, participants were instructed that both CS+1 and CS+2 would be followed by the US, but only CS+1 was actually paired with the US. The absence of the US after CS+2 was explained in such a way that participants would not doubt the instructions about the CS+2-US relation. After the training phase, a test phase was carried out. In this phase, participants expected the US after both CS+s but none of the CS+s was actually paired with the US. During test, self-reported fear was initially higher for CS+1 than for CS+2, which indicates that the experience of actual CS-US pairings adds to instructions about these pairings. On the other hand, the CS+s elicited similar skin conductance responses and US expectancies. Theoretical and clinical implications are discussed. PMID:24465447

  20. Short-term frequency stability of the Rb-87 maser.

    NASA Technical Reports Server (NTRS)

    Tetu, M.; Busca, G.; Vanier, J.

    1973-01-01

    Measurements of the short-term stability of the Rb-87 maser as a function of the maser power output and the receiver cutoff frequency are reported. The experimental data are compared to theoretical results obtained from an approximate theory. In this theory the transfer function of the maser for thermal noise is derived, and the spectral density of the phase fluctuations is calculated. An analytical expression for the 'Allan variance' is also given. A comparison of the stability of the Rb-87 maser with existing frequency standards shows its superiority for averaging times less than 1 sec.

  1. Distribution of 137Cs in soils due to the Goiânia accident and decisions for remedial action during the recovery phase.

    PubMed

    Amaral, E C; Vianna, M E; Godoy, J M; Rochedo, E R; Campos, M J; do Rio, M A; Oliveira, J P; Pereira, J C; Reis, W G

    1991-01-01

    In September 1987, a powder radioactive source was removed from a teletherapy machine in Goiânia, Brazil. Subsequently, it was ruptured in a residential garden causing the dissemination of 137Cs throughout the city. Soil resuspension processes and burial of contaminated house waste in unused gardens were the major contributors to the Cs dissemination in soils at the secondary contaminated sites. Only locations within a radius of 50 m from the primary contaminated sites presented the need for remedial action. The radiation dose-rate measurements and the soil profiles were good indicators of the extent of the secondary contamination and were fundamental for the decisions taken regarding decontamination procedures. In cases of surface contamination, 60% on average of the total activity remained in the upper 1.5-cm layer over the first 5 mo after the accident, and topsoil removal proved to be an effective procedure for decontamination. PMID:1983991

  2. A conserved arginine near the filter of Kir1.1 controls Rb/K selectivity

    PubMed Central

    Sackin, Henry; Nanazashvili, Mikheil; Li, Hui; Palmer, Lawrence G.; Walters, D. Eric

    2010-01-01

    ROMK (Kir1.1) channels are important for K secretion and recycling in the collecting duct, connecting tubule and thick ascending limb of the mammalian nephron. We have identified a highly conserved Arg in the P loop of the channel near the selectivity filter that controls Rb/K selectivity. Mutation of this Arg to a Tyr (R128Y-Kir1.1b, R147Y-Kir1.1a) increased the macroscopic conductance ratio, GRb/GK by 17 ± 3 fold and altered the selectivity sequence from NH4 > K > Tl > RbCs in wt-Kir1.1 to: Rb > Cs > Tl > NH4 ≫ K in R128Y, without significant change in the high K/Na permeability ratio of Kir1.1. R128M produced similar, but smaller, increases in Rb, Tl, NH4 and Cs conductance relative to K. R128Y remained susceptible to block by both external Ba and the honeybee toxin, TPNQ, although R128Y had a reduced affinity for TPNQ, relative to wild-type. The effect of R128Y-Kir1.1b on the GRb/GK ratio can be partly explained by a larger single-channel Rb conductance (12.4 ± 0.5 pS) than K conductance (<1.5 pS) in this mutant. The kinetics of R128Y gating at -120 mV with Rb as the permeantion were similar to those of wt-Kir1.1 conducting Rb, but with a longer open time (129 ms vs. 6 ms for wt) and two closed states (13 ms, 905 ms), resulting in an open probability (Po) of 0.5, compared to a Po of 0.9 for wt-Kir1.1, which had a single closed state of 1 ms at -120 mV. single-channel R128Y rectification was eliminated in excised, inside-out patches with symmetrical Rb solutions. The large increase in the Rb/K conductance ratio, with no change in K/Na permeability or rectification, is consistent with R128Y-Kir1.1b causing a subtle change in the selectivity filter, perhaps by disruption of an intra-subunit salt bridge (R128-e118) near the filter. PMID:20458182

  3. NMR studies of Phase Transitions in Alkali Metal Films on Glass Substrates

    NASA Astrophysics Data System (ADS)

    Ishikawa, K.; Patton, B.; Jau, Y.-Y.; Happer, W.

    2006-05-01

    We report NMR spectra of thin ^87Rb films on glass in an investigation of the ``curing'' process which is commonly observed in alkali cells. The cells were cycled in temperature over a range of 5 C to 170 C and the rubidium solid-liquid phase transition was studied. The spectra of these two phases are resolvable at 9.4 T because of their different Knight shifts. Hysteresis in the observed phases confirmed reports of a curing phenomenon, and after time a supercooled liquid Rb peak could be detected at temperatures far below the predicted freezing point of 39 C. Moreover, a third NMR peak was observed at temperatures below the melting point whose frequency varied with temperature and spanned the solid and liquid frequency ranges. To our knowledge, this is the first study to characterize this additional resonance. We have also performed analogous measurements on ^133Cs films.

  4. Temperature and composition phase diagram in the iron-based ladder compounds Ba 1 - x Cs x Fe 2 Se 3

    SciTech Connect

    Hawai, Takafumi; Nambu, Yusuke; Ohgushi, Kenya; Du, Fei; Hirata, Yasuyuki; Avdeev, Maxim; Uwatoko, Yoshiya; Sekine, Yurina; Fukazawa, Hiroshi; Ma, Jie; Chi, Songxue; Ueda, Yutaka; Yoshizawa, Hideki; Sato, Taku J.

    2015-05-28

    We investigated the iron-based ladder compounds (Ba,Cs)Fe₂Se₃. Their parent compounds BaFe₂Se₃ and CsFe₂Se₃ have different space groups, formal valences of Fe, and magnetic structures. Electrical resistivity, specific heat, magnetic susceptibility, x-ray diffraction, and powder neutron diffraction measurements were conducted to obtain a temperature and composition phase diagram of this system. Block magnetism observed in BaFe₂Se₃ is drastically suppressed with Cs doping. In contrast, stripe magnetism observed in CsFe₂Se₃ is not so fragile against Ba doping. A new type of magnetic structure appears in intermediate compositions, which is similar to stripe magnetism of CsFe₂Se₃, but interladder spin configuration is different. Intermediate compounds show insulating behavior, nevertheless a finite T-linear contribution in specific heat was obtained at low temperatures.

  5. DFT study of Rb-TFA structure after high-pressure action

    NASA Astrophysics Data System (ADS)

    Scholtzová, Eva

    2011-12-01

    The pressure-induced A-B phase transition of synthetic Rb-tetra-ferri-annite (Rb-TFA) mica was studied theoretically by means of Density Functional Theory (DFT) method. The calculations show that Rb-TFA keeps a Franzini A-type structure up to at least 5.39 GPa of pressure, whereas at higher pressure, it transforms to a Franzini B-type structure. The negative value of the tetrahedral rotation angle α = -4.68° has appeared at 5.56 GPa of calculated pressure. This result is in a relatively good agreement with experimentally estimated phase transition area in the range of 3.36-3.84 GPa. The energy difference between the A and B structures is very small (ΔE = 8 kJ/mol). The detailed analysis of the optimized structural data shows minimal changes in the structure of Rb-TFA after the pressure-induced phase transition.

  6. Inorganic materis for anomalous-dispersion phase-matched second harmonic generation: Rubidium titanyl arsenate isomorphs, Rb[Ti{sub 1-2x}Ln{sub x}Nb{sub x}]OAsO{sub 4}

    SciTech Connect

    Anderson, M.T.; Phillips, M.L.F.; Stucky, G.D.

    1993-12-31

    We report the synthesis and optical properties of Rb[Ti{sub 1-2x}Ln{sub x}Nb{sub x}]OAsO{sub 4}. The solid solubility of lanthanide ions in the materials decreases exponentially as the size of the lanthanide ion increases. The materials exhibit absorption spectra characteristic of the particular lanthanide ion in the structure. The spectral regions between absorption peaks are transparent and will allow the transmission of fundamental and second-harmonic radiation. The charge transfer band is red-shifted 0 to 27 nm relative to RbTiOAsO{sub 4} (midpoint 331 nm). Second-harmonic intensities measured at 532 nm decrease exponentially as lanthanide ion concentration increases.

  7. Pressure-induced metathesis reaction to sequester Cs.

    PubMed

    Im, Junhyuck; Seoung, Donghoon; Lee, Seung Yeop; Blom, Douglas A; Vogt, Thomas; Kao, Chi-Chang; Lee, Yongjae

    2015-01-01

    We report here a pressure-driven metathesis reaction where Ag-exchanged natrolite (Ag16Al16Si24O80·16H2O, Ag-NAT) is pressurized in an aqueous CsI solution, resulting in the exchange of Ag(+) by Cs(+) in the natrolite framework forming Cs16Al16Si24O80·16H2O (Cs-NAT-I) and, above 0.5 GPa, its high-pressure polymorph (Cs-NAT-II). During the initial cation exchange, the precipitation of AgI occurs. Additional pressure and heat at 2 GPa and 160 °C transforms Cs-NAT-II to a pollucite-related, highly dense, and water-free triclinic phase with nominal composition CsAlSi2O6. At ambient temperature after pressure release, the Cs remains sequestered in a now monoclinic pollucite phase at close to 40 wt % and a favorably low Cs leaching rate under back-exchange conditions. This process thus efficiently combines the pressure-driven separation of Cs and I at ambient temperature with the subsequent sequestration of Cs under moderate pressures and temperatures in its preferred waste form suitable for long-term storage at ambient conditions. The zeolite pollucite CsAlSi2O6·H2O has been identified as a potential host material for nuclear waste remediation of anthropogenic (137)Cs due to its chemical and thermal stability, low leaching rate, and the large amount of Cs it can contain. The new water-free pollucite phase we characterize during our process will not display radiolysis of water during longterm storage while maintaining the Cs content and low leaching rate. PMID:25515673

  8. Melt Processed Single Phase Hollandite Waste Forms For Nuclear Waste Immobilization: Ba{sub 1.0}Cs{sub 0.3}A{sub 2.3}Ti{sub 5.7}O{sub 16}; A = Cr, Fe, Al

    SciTech Connect

    Brinkman, Kyle; Marra, James; Amoroso, Jake; Conradson, Steven D.; Tang, Ming

    2013-09-23

    Cs is one of the more problematic fission product radionuclides to immobilize due to its high volatility at elevated temperatures, ability to form water soluble compounds, and its mobility in many host materials. The hollandite structure is a promising crystalline host for Cs immobilization and has been traditionally fabricated by solid state sintering methods. This study presents the structure and performance of Ba{sub 1.0}Cs{sub 0.3}A{sub 2.3}Ti{sub 5.7}O{sub 16}; A = Cr, Fe, Al hollandite fabricated by melt processing. Melt processing is considered advantageous given that melters are currently in use for High Level Waste (HLW) vitrification in several countries. This work details the impact of Cr additions that were demonstrated to i) promote the formation of a Cs containing hollandite phase and ii) maintain the stability of the hollandite phase in reducing conditions anticipated for multiphase waste form processing.

  9. Adsorption-site investigation of Rb/Cu(111) using the x-ray standing-wave method

    NASA Astrophysics Data System (ADS)

    Shi, X.; Su, C.; Heskett, D.; Berman, L.; Kao, C. C.; Bedzyk, M. J.

    1994-05-01

    We have carried out a back reflection x-ray standing-wave investigation to study the adsorbate-substrate bond length and bonding site for the system Rb/Cu(111). Our low-energy electron diffraction study showed an ordered (2×2) phase for one monolayer of Rb on Cu(111) (θ=0.25). By measuring both the (111) and (111¯) Bragg reflections at this coverage, we determine the Rb adsorption to be in the top site. We observe a high degree of order in the Rb overlayer perpendicular to the surface, with large disorder parallel to the surface.

  10. Improving CS regulations.

    SciTech Connect

    Nesse, R.J.; Scheer, R.M.; Marasco, A.L.; Furey, R.

    1980-10-01

    President Carter issued Executive Order 12044 (3/28/78) that required all Federal agencies to distinguish between significant and insignificant regulations, and to determine whether a regulation will result in major impacts. This study gathered information on the impact of the order and the guidelines on the Office of Conservation and Solar Energy (CS) regulatory practices, investigated problems encountered by the CS staff when implementing the order and guidelines, and recommended solutions to resolve these problems. Major tasks accomplished and discussed are: (1) legislation, Executive Orders, and DOE Memoranda concerning Federal administrative procedures relevant to the development and analysis of regulations within CS reviewed; (2) relevant DOE Orders and Memoranda analyzed and key DOE and CS staff interviewed in order to accurately describe the current CS regulatory process; (3) DOE staff from the Office of the General Counsel, the Office of Policy and Evaluation, the Office of the Environment, and the Office of the Secretary interviewed to explore issues and problems encountered with current CS regulatory practices; (4) the regulatory processes at five other Federal agencies reviewed in order to see how other agencies have approached the regulatory process, dealt with specific regulatory problems, and responded to the Executive Order; and (5) based on the results of the preceding four tasks, recommendations for potential solutions to the CS regulatory problems developed. (MCW)

  11. A Raman study of RbSnBr 3

    NASA Astrophysics Data System (ADS)

    Kuok, M. H.; Tan, L. S.; Shen, Z. X.; Huan, C. H.; Mok, K. F.

    1996-02-01

    The Raman spectrum of rubidium tribromostannate, RbSnBr 3, has been measured as a function of temperature between 14 and 520 K. On cooling the RbSnBr 3 crystal, the low-energy portion of the spectrum undergoes marked changes, suggesting the occurrence of a structural phase transition. A low-lying wing feature appears below 170 K, while the lowest-energy lattice band is found to soften from 19.6 cm -1 at 14 K to ca. 15 cm -1 at 140 K. The results are interpreted on the basis of a tin coordination of octahedral bromide ions. The phase transition is probably displacive in character and is associated with a rotation of the SnBr 6 octahedra.

  12. Layered polymeric nitrogen in RbN3 at high pressures.

    PubMed

    Wang, Xiaoli; Li, Jianfu; Xu, Ning; Zhu, Hongyang; Hu, Ziyu; Chen, Li

    2015-01-01

    The structural evolutionary behaviors of nitrogen in RbN3 have been studied up to 300 GPa using a particle swarm optimization structure searching method combined with density functional calculations. Three stable new phases with P-1, P6/mmm and C2/m structure at pressure of 30, 50 and 200 GPa are identified for the first time. The analysis of the crystal structures of three new predicated phases reveals that the transition of N3- ions goes from linear molecules to polymeric chains, benzene-like rings and then to polymeric layers induced by pressure. The electronic structures of three predicted phases reveal that the structural changes are accompanied and driven by the change of orbital hybridization of N atoms from sp to sp(2) and finally to partial sp(3). Most interestingly, the Rb atoms show obvious transition metal-like properties through the occupation of 4d orbitals in high-pressure phases. Moreover, the Rb atoms are characterized by strong hybridization between 4d orbitals of Rb and 2p orbitals of N in C2/m structure. Our studies complete the structural evolution of RbN3 under pressure and reveal for the first time that the Rb atoms in rubidium nitride possess transition element-like properties under pressure. PMID:26564812

  13. Layered polymeric nitrogen in RbN3 at high pressures

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoli; Li, Jianfu; Xu, Ning; Zhu, Hongyang; Hu, Ziyu; Chen, Li

    2015-11-01

    The structural evolutionary behaviors of nitrogen in RbN3 have been studied up to 300 GPa using a particle swarm optimization structure searching method combined with density functional calculations. Three stable new phases with P-1, P6/mmm and C2/m structure at pressure of 30, 50 and 200 GPa are identified for the first time. The analysis of the crystal structures of three new predicated phases reveals that the transition of N3- ions goes from linear molecules to polymeric chains, benzene-like rings and then to polymeric layers induced by pressure. The electronic structures of three predicted phases reveal that the structural changes are accompanied and driven by the change of orbital hybridization of N atoms from sp to sp2 and finally to partial sp3. Most interestingly, the Rb atoms show obvious transition metal-like properties through the occupation of 4d orbitals in high-pressure phases. Moreover, the Rb atoms are characterized by strong hybridization between 4d orbitals of Rb and 2p orbitals of N in C2/m structure. Our studies complete the structural evolution of RbN3 under pressure and reveal for the first time that the Rb atoms in rubidium nitride possess transition element-like properties under pressure.

  14. Layered polymeric nitrogen in RbN3 at high pressures

    PubMed Central

    Wang, Xiaoli; Li, Jianfu; Xu, Ning; Zhu, Hongyang; Hu, Ziyu; Chen, Li

    2015-01-01

    The structural evolutionary behaviors of nitrogen in RbN3 have been studied up to 300 GPa using a particle swarm optimization structure searching method combined with density functional calculations. Three stable new phases with P-1, P6/mmm and C2/m structure at pressure of 30, 50 and 200 GPa are identified for the first time. The analysis of the crystal structures of three new predicated phases reveals that the transition of N3− ions goes from linear molecules to polymeric chains, benzene-like rings and then to polymeric layers induced by pressure. The electronic structures of three predicted phases reveal that the structural changes are accompanied and driven by the change of orbital hybridization of N atoms from sp to sp2 and finally to partial sp3. Most interestingly, the Rb atoms show obvious transition metal-like properties through the occupation of 4d orbitals in high-pressure phases. Moreover, the Rb atoms are characterized by strong hybridization between 4d orbitals of Rb and 2p orbitals of N in C2/m structure. Our studies complete the structural evolution of RbN3 under pressure and reveal for the first time that the Rb atoms in rubidium nitride possess transition element-like properties under pressure. PMID:26564812

  15. Pulsed Optically Pumped Rb clock

    NASA Astrophysics Data System (ADS)

    Micalizio, S.; Levi, F.; Godone, A.; Calosso, C. E.; François, B.; Boudot, R.; Affolderbach, C.; Kang, S.; Gharavipour, M.; Gruet, F.; Mileti, G.

    2016-06-01

    INRIM demonstrated a Rb vapour cell clock based on pulsed optical pumping (POP) with unprecedented frequency stability performances, both in the short and in the medium-long term period. In the frame of a EMRP project, we are developing a new clock based on the same POP principle but adopting solutions aimed at reducing the noise sources affecting the INRIM clock. At the same time, concerning possible technological applications, particular care are devoted in the project to reduce the size and the weight of the clock, still keeping the excellent stability of the INRIM clock. The paper resumes the main results of this activity.

  16. Quasi-one-dimensional electronic structure in orthorhombic RbC[sub 60

    SciTech Connect

    Chauvet, O.; Oszlanyi, G.; Forro, L. ); Stephens, P.W. ); Tegze, M.; Faigel, G.; Janossy, A. )

    1994-04-25

    X-ray diffraction studies show that the stable phase of the alkali fullerene RbC[sub 60] is orthorhombic ([ital o]-RbC[sub 60]) below 350 K. C[sub 60] molecules form chains along [bold a] with an unusually short spacing of 9.12 A and magnetic properties suggest that [ital o]-RbC[sub 60] is a quasi-1D metal with a transition to a spin density wave ground state at 50 K. The high temperature fcc phase of RbC[sub 60] may be stabilized below 300 K by quenching from 500 K; it is paramagnetic above 300 K and transforms into a nonmagnetic ground state beween 300 and 250 K.

  17. Ba2+-inhibitable /sup 86/Rb+ fluxes across membranes of vesicles from toad urinary bladder

    SciTech Connect

    Garty, H.; Civan, M.M.

    1987-01-01

    /sup 86/Rb+ fluxes have been measured in suspensions of vesicles prepared from the epithelium of toad urinary bladder. A readily measurable barium-sensitive, ouabain-insensitive component has been identified; the concentration of external Ba2+ required for half-maximal inhibition was 0.6 mM. The effects of externally added cations on /sup 86/Rb+ influx and efflux have established that this pathway is conductive, with a selectivity for K+, Rb+ and Cs+ over Na+ and Li+. The Rb+ uptake is inversely dependent on external pH, but not significantly affected by internal Ca2+ or external amiloride, quinine, quinidine or lidocaine. It is likely, albeit not yet certain, that the conductive Rb+ pathway is incorporated in basolateral vesicles oriented right-side-out. It is also not yet clear whether this pathway comprises the principle basolateral K+ channel in vivo, and that its properties have been unchanged during the preparative procedures. Subject to these caveats, the data suggest that the inhibition by quinidine of Na+ transport across toad bladder does not arise primarily from membrane depolarization produced by a direct blockage of the basolateral channels. It now seems more likely that the quinidine-induced elevation of intracellular Ca2+ activity directly blocks apical Na+ entry.

  18. Near-yrast, medium-spin, excited states of {sup 91}Rb, {sup 93}Rb, and {sup 95}Rb

    SciTech Connect

    Simpson, G. S.; Sieja, K.; Dare, J. A.; Orlandi, R.; Smith, A. G.; Tsekhanovich, I.; Varley, B. J.; Durell, J. L.; Smith, J. F.; Jolie, J.; Linneman, A.; Scherillo, A.; Soldner, T.; Faust, H.; Zlomaniec, A.; Rzaca-Urban, T.; Ahmad, I.; Greene, J. P.

    2010-08-15

    The medium-spin structure of the nuclei {sup 93}Rb and {sup 95}Rb is studied following the neutron-induced fission of {sup 235}U at the PF1B neutron guide, using the FIFI spectrometer, and at the Lohengrin mass spectrometer of the Institut Laue-Langevin Grenoble. These nuclei, plus {sup 91}Rb, are also studied following the spontaneous fission of {sup 248}Cm and {sup 252}Cf sources, using the EUROGAM-II and Gammasphere detector arrays, respectively. A high-spin isomeric state, with a half-life of 111(11) ns, is found in {sup 93}Rb at an excitation energy of 4422.4 keV, which most likely corresponds to the fully aligned [{pi}(g{sub 9/2}) x {nu}(g{sub 7/2}h{sub 11/2})]{sub 27/2}{sup -} configuration. An analogous configuration is proposed for the 5297.9-keV level observed in {sup 91}Rb. A new E3 decay branch of the 1133.9-keV isomer in {sup 91}Rb is found, for which the rather low transition rate of B(E3)=3.8(10) W.u. is determined. The energy of the isomeric state of {sup 95}Rb is now proposed to be at 810.6 keV, with a spin of (9/2{sup +}), and its half-life determined to be T{sub 1/2}=94(7) ns. A cascade of prompt transitions is observed on top of the 810.6-keV isomer in {sup 95}Rb. The near-yrast structures of {sup 91}Rb, {sup 93}Rb, and {sup 95}Rb are compared to the results of shell-model calculations, which support the proposed 27/2{sup -} interpretation of states in {sup 91}Rb and {sup 93}Rb. An analogous 27/2{sup -} state is expected to occur in {sup 95}Rb, as a long-lived isomer at 3.24 MeV. No such isomeric decay could be observed in a measurement using the Lohengrin spectrometer, which shows that, if it exists, its population, following the fission of {sup 235}U, is at least four times lower than that of the analogous 27/2{sup -} isomer in {sup 97}Y.

  19. Determination of the hyperfine structure constants of the 87Rb and 85Rb 4 D5 /2 state and the isotope hyperfine anomaly

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Liu, Huifeng; Yang, Guang; Yang, Baodong; Wang, Junmin

    2014-11-01

    The hyperfine structure (hfs) splittings of the 4 D5 /2 state for two isotopes of 87Rb and 85Rb atoms are measured based on double-resonance optical pumping spectra in a 5 S1 /2-5 P3 /2-4 D5 /2 ladder-type atomic system. The frequency calibration is performed by employing a wideband fiber-pigtailed phase-type electro-optic modulator together with a Fabry-Pérot cavity to cancel the error arising from nonlinear frequency scanning. The hfs magnetic dipole constant A of the 4 D5 /2 state is determined to be -16.801 ± 0.005 MHz for 87Rb and -4.978 ± 0.004 MHz for 85Rb . The hfs electric quadrupole constant B of the 4 D5 /2 state is determined to be 3.645 ± 0.030 MHz for 87Rb and 6.560 ± 0.052 MHz for 85Rb . The values of A and B for the 87Rb4 D5 /2 state are twice as accurate as previous work with thermal atoms using a femtosecond laser comb and the values of A and B for the 85Rb4 D5 /2 state are 3 times and 25 times more accurate than previous work in laser-cooled atoms using Fabry-Pérot interferometer, respectively. According to this high precision of the hfs constants and the previously measured nuclear g factors of the two isotopes, the value of the d -electron hyperfine anomaly 87Δ85(4 D5 /2 ) is derived to be -0.0041 ± 0.0009.

  20. Cs[H2NB2(C6F5)6] Featuring an Unequivocal 16-Coordinate Cation.

    PubMed

    Pollak, David; Goddard, Richard; Pörschke, Klaus-Richard

    2016-08-01

    Cesium bis(perfluoro-triphenylborane)amide, Cs[H2NB2(C6F5)6] (1), has been prepared by the reaction of sodium salt and CsF in dichloromethane and water. The compound is exceptional for a [H2NB2(C6F5)6](-) salt in that it contains a monatomic solute-free cation. Determination of the molecular structure revealed a novel C2 symmetrical conformation of the weakly coordinating [H2NB2(C6F5)6](-) anion, which gives rise to an unprecedented 16-coordinate (CN 16) Cs(+) cation in a likewise unprecedented tetracosahedral arrangement of F atoms. The poor solubility of 1 allows nearly quantitative separation of Cs(+) from water, which suggests potential applications as an effective (134/137)Cs remover from nuclear waste solutions, administration as an antidote for (134/137)Cs poisoning, and use for (131/137)Cs radiotherapy (brachytherapy). Rb[H2NB2(C6F5)6]·CH2Cl2 (2) has also been characterized, featuring two inequivalent Rb(+) cations having CN 10, one of which involves Rb(+)(η(2)-Cl2CH2)2 coordination. PMID:27267866

  1. EXTRAGALACTIC CS SURVEY

    SciTech Connect

    Bayet, E.; Viti, S.; Aladro, R.; MartIn, S.; MartIn-Pintado, J.

    2009-12-10

    We present a coherent and homogeneous multi-line study of the CS molecule in nearby (D < 10 Mpc) galaxies. We include, from the literature, all the available observations from the J = 1-0 to the J = 7-6 transitions toward NGC 253, NGC 1068, IC 342, Henize 2-10, M 82, the Antennae Galaxies, and M 83. We have, for the first time, detected the CS(7-6) line in NGC 253, M 82 (both in the northeast and southwest molecular lobes), NGC 4038, M 83 and tentatively in NGC 1068, IC 342, and Henize 2-10. We use the CS molecule as a tracer of the densest gas component of the interstellar medium in extragalactic star-forming regions, following previous theoretical and observational studies by Bayet et al. In this first paper out of a series, we analyze the CS data sample under both local thermodynamical equilibrium (LTE) and non-LTE (large velocity gradient) approximations. We show that except for M 83 and Overlap (a shifted gas-rich position from the nucleus NGC 4039 in the Antennae Galaxies), the observations in NGC 253, IC 342, M 82-NE, M 82-SW, and NGC 4038 are not well reproduced by a single set of gas component properties and that, at least, two gas components are required. For each gas component, we provide estimates of the corresponding kinetic temperature, total CS column density, and gas density.

  2. Rb-Sr Isotopic Systematics of Alkali-Rich Fragments in the Yamato-74442 LL-Chondritic Breccia

    NASA Technical Reports Server (NTRS)

    Yokoyama, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simo, J. I.; Tappa, M. J.; Yoneda, S.

    2012-01-01

    Alkali-rich igneous fragments were identified in the brecciated LL-chondrites, Kr henberg (LL5)], Bhola (LL3-6) and Yamato (Y)-74442 (LL4), and show characteristic fractionation patterns of alkaline elements. The K-Rb-Cs-rich fragments in Kr henberg, Bhola, and Y-74442 are very similar in mineralogy and petrography (olivine + pyroxene + glass), suggesting that they could have come from related precursor materials. We have undertaken Rb-Sr isotopic studies on alkali-rich fragments in Y-74442 to precisely determine their crystallization ages and the isotopic signatures of their precursor material(s).

  3. pRB plays an essential role in cell cycle arrest induced by DNA damage

    PubMed Central

    Harrington, Elizabeth A.; Bruce, Jacqueline L.; Harlow, Ed; Dyson, Nicholas

    1998-01-01

    To maintain genome stability, cells with damaged DNA must arrest to allow repair of mutations before replication. Although several key components required to elicit this arrest have been discovered, much of the pathway remains elusive. Here we report that pRB acts as a central mediator of the proliferative block induced by a diverse range of DNA damaging stimuli. Rb−/− mouse embryo fibroblasts are defective in arrest after γ-irradiation, UV irradiation, and treatment with a variety of chemotherapeutic drugs. In contrast, the pRB related proteins p107 and p130 do not play an essential part in the DNA damage response. pRB is required specifically for the G1/S phase checkpoint induced by γ-irradiation. Despite a defect in G1/S phase arrest, levels of p53 and p21 are increased normally in Rb−/− cells in response to γ-irradiation. These results lead us to propose a model in which pRB acts as an essential downstream target of the DNA damage-induced arrest pathway. The ability of pRB to prevent replication of damaged DNA is likely to inhibit the propagation of carcinogenic mutations and may therefore contribute to its role as a tumor suppressor. Furthermore, because many cancer therapies act by damaging DNA, these findings also have implications for the treatment of tumors in which pRB is inactivated. PMID:9751770

  4. Antiferromagnetism in a bosonic mixture of rubidium ({sup 87}Rb) and potassium ({sup 41}K)

    SciTech Connect

    Shrestha, Uttam

    2010-10-15

    We simulate the experimental possibility of observing antiferromagnetic (AF) order in bosonic mixtures of rubidium ({sup 87}Rb) and potassium ({sup 41}K) in a two-dimensional optical lattice in the presence of harmonic confinement. By tuning the interspecies interactions and the lattice heights, we have found the ground states, within the mean-field approximation, that interpolate from phase separation to AF order. For a moderate lattice height, the coexistence of the Mott and AF phases is possible for the Rb atoms whereas the K atoms remain in the AF-superfluid phase. This observation may provide an experimentally feasible route to hitherto unobserved AF order for {sup 87}Rb-{sup 41}K mixtures.

  5. Reaction-transport-mechanical (RTM) simulator Sym.CS: Putting together water-rock interaction, multi-phase and heat flow, composite petrophysics model, and fracture mechanics

    NASA Astrophysics Data System (ADS)

    Paolini, C.; Park, A. J.; Mellors, R. J.; Castillo, J.

    2009-12-01

    A typical CO2 sequestration scenario involves the use of multiple simulators for addressing multiphase fluid and heat flow, water-rock interaction and mass-transfer, rock mechanics, and other chemical and physical processes. The benefit of such workflow is that each model can be constrained rigorously; however, the drawback is final modeling results may achieve only a limited extent of the theoretically possible capabilities of each model. Furthermore, such an approach in modeling carbon sequestration cannot capture the nonlinearity of the various chemical and physical processes. Hence, the models can only provide guidelines for carbon sequestration processes with large margins of error. As an alternative, a simulator is being constructed by a multi-disciplinary team with the aim of implementing a large array of fundamental phenomenologies, including, but not limited to: water-rock interaction using elemental mass-balance and explicit mass-transfer and reaction coupling methods; multi-phase and heat flow, including super-critical CO2 and oil; fracture mechanics with anisotropic permeabilities; rheological rock mechanics based on incremental stress theory; and a composite petrophysics model capable of describing changing rock composition and properties. The modules representing the processes will be solved using a layered iteration method, with the goal of capturing the nonlinear feedback among all of the processes. The simulator will be constructed using proven optimization and modular, object-oriented, and service-oriented programming methods. Finally, a novel AJAX (asynchronous JavaScript and XML) user interface is being tested to host the simulator that will allow usage through an Internet browser. Currently, the water-rock interaction, composite petrophysics, and multi-phase fluid and heat flow modules are available for integration. Results of the water-rock interaction and petrophysics coupling has been used to model interaction between a CO2-charged water and

  6. High-field measurement of the 129Xe-Cs binary spin-exchange rate coefficient

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu; Kuzma, Nicholas N.; Happer, William

    2004-03-01

    We report the first measurement of the binary spin-exchange rate coefficient κ in the ^129Xe-Cs system. Data were taken using ^129Xe NMR in glass cells containing isotopically enriched xenon gas at pressures on the order of atmospheres and a small amount of liquid Cs metal, in the temperature range from 120 to 140^rcC and at a magnetic field of 9.4 T. The contribution of CsXe van der Waals molecules to spin exchange should have been nearly eliminated by the high magnetic field, as confirmed by our measurements of the ^129Xe longitudinal relaxation time T1 in a series of cells with various densities of xenon. The Cs atomic number density [Cs] was controlled by the cell temperature, and was experimentally determined by analysis of the Faraday rotation of linearly polarized probe laser light. We measured κ = d (T_1-1)/d[Cs]= (2.81± 0.2) × 10-16 cm^3 s-1 . This is about 60% larger than the previously measured rate coefficient for the ^129Xe-Rb system(Y.-Y. Jau, N. N. Kuzma, and W. Happer, Phys. Rev. A 66, 052710 (2002).), κ =d (T_1-1)/d[Rb]= (1.75± 0.12) × 10-16 cm^3 s-1 . A comparison with theory(Y.-Y. Jau, N. N. Kuzma, and W. Happer, Phys. Rev. A 67, 022720 (2003).) will be discussed.

  7. CsEuBr3: Crystal structure and its role in the photostimulation of CsBr :Eu2+

    NASA Astrophysics Data System (ADS)

    Hesse, S.; Zimmermann, J.; von Seggern, H.; Ehrenberg, H.; Fuess, H.; Fasel, C.; Riedel, R.

    2006-10-01

    CsBr :Eu2+ has recently been investigated as a photostimulable x-ray storage phosphor with great potential for application in high-resolution image plates. In a recent paper Hackenschmied et al. [J. Appl. Phys. 93, 5109 (2003)] suggested that segregations of CsEuBr3 or Cs4EuBr6 formed within CsBr :Eu2+ during annealing are responsible for an increase in the photostimulated luminescence (PSL) yield. In this work single crystals of CsEuBr3 were prepared by a one step synthesis and identified by x-ray diffraction (XRD) analysis as single phase perovskites. It was concluded that, after preparation, CsEuBr3 degrades in normal atmosphere into at least two phases, one of which is the orthorhombic structure of Cs2EuBr5•10H2O. The XRD powder diffraction pattern of this compound is very similar to that of the segregations observed within CsBr :Eu2+ and reported by Hackenschmied et al. However, the increased PSL yield in CsBr :Eu2+ after annealing cannot be due to the segregations, because the trivalent nature of the europium in the segregations renders them PSL inactive.

  8. Phase I Trial of Anti-CS1 Monoclonal Antibody Elotuzumab in Combination With Bortezomib in the Treatment of Relapsed/Refractory Multiple Myeloma

    PubMed Central

    Jakubowiak, Andrzej J.; Benson, Don M.; Bensinger, William; Siegel, David S.D.; Zimmerman, Todd M.; Mohrbacher, Ann; Richardson, Paul G.; Afar, Daniel E.H.; Singhal, Anil K.; Anderson, Kenneth C.

    2012-01-01

    Purpose To evaluate the maximum-tolerated dose (MTD), safety, and efficacy of elotuzumab in combination with bortezomib in patients with relapsed or relapsed and refractory multiple myeloma (MM). Patients and Methods Elotuzumab (2.5, 5.0, 10, or 20 mg/kg intravenously [IV]) and bortezomib (1.3 mg/m2 IV) were administered on days 1 and 11 and days 1, 4, 8, and 11, respectively, in 21-day cycles by using a 3 + 3 dose-escalation design. Patients with stable disease or better after four cycles could continue treatment until disease progression or unexpected toxicity. Responses were assessed during each cycle by using European Group for Blood and Marrow Transplantation (EBMT) criteria. Results Twenty-eight patients with a median of two prior therapies were enrolled; three patients each received 2.5, 5.0, and 10 mg/kg of elotuzumab and 19 received 20 mg/kg (six during dose escalation and 13 during an expansion phase). No dose-limiting toxicities were observed during cycle 1 of the dose-escalation phase, and the MTD was not reached up to the maximum planned dose of 20 mg/kg. The most frequent grade 3 to 4 adverse events (AEs) were lymphopenia (25%) and fatigue (14%). Two elotuzumab-related serious AEs of chest pain and gastroenteritis occurred in one patient. An objective response (a partial response or better) was observed in 13 (48%) of 27 evaluable patients and in two (67%) of three patients refractory to bortezomib. Median time to progression was 9.46 months. Conclusion The combination of elotuzumab and bortezomib was generally well-tolerated and showed encouraging activity in patients with relapsed/refractory MM. PMID:22291084

  9. Determination of low (137)Cs concentration in seawater using ammonium 12-molybdophosphate adsorption and chemical separation method.

    PubMed

    Park, J H; Chang, B U; Kim, Y J; Seo, J S; Choi, S W; Yun, J Y

    2008-12-01

    A new method has been developed for analyzing (137)Cs in a small volume of seawater. Ammonium 12-molybdophosphate (AMP) was used two times during pretreatment procedure. The first step was to adsorb (137)Cs in seawater samples into AMP in order to reduce sample volume, and the second was to remove (87)Rb, interference nuclide for beta counting. The AMP adsorbing (137)Cs was dissolved by sodium hydroxide solution, and then (137)Cs was finally formed to be cesium chloroplatinate precipitate by adding 10% hexachloroplatinic acid. The beta rays emitted from (137)Cs were measured with a low background gas-proportional alpha/beta counter. This method was applied to several seawater samples taken in the East Sea of Korea. Compared to the routinely used gamma-spectrometry method, this new AMP method was reliable and suitable for analyzing (137)Cs in deep seawater. PMID:18799246

  10. Energetics and structural stability of Cs3C60

    SciTech Connect

    Saito, Susumu; Umemoto, Koichiro; Louie, Steven G.; Cohen, MarvinL.

    2003-12-15

    Using the ab initio pseudo potential total-energy method and the density-functional theory, we study the energetics of face-centered-cubic Cs3C60 which is a material of great interest as a possible high transition-temperature superconductor. At the optimized lattice constant the volume per C60 is found to be smaller than the most stable hexagon-coordination A15 phase, while the total energy of the fcc phase is about 0.9 eV higher than the A15 phase. These results indicate that a low-temperature and high-pressure synthesis method might be a possible way to produce the fcc Cs3C60 phase. In addition, it is also found that the A15 Cs3C60 should show a phase transformation from a hexagon-coordination phase to a pentagon-coordination phase under hydrostatic pressure.