Nd3+-doped TeO2–PbF2–AlF3 glasses for laser applications

A study of the optical properties of Nd3+ ion in TeO2–PbF2–AlF3 glasses has been carried out for different Nd3+ concentrations. Based on the Judd–Ofelt theory, intensity parameters and radiative properties were determined from the absorption spectra. Focusing on the suitability of this host for laser applications, the spectroscopic quality factor v was obtained with a value of 1.07, a value of the order of other compositions proposed as laser hosts. For the most intense emission corresponding with the 4F3/2?4I11/2 transition (1.06 lm), the absorption and emission and have been calculated with values of 1.20 10 20 cm2, 2.08 10 20 cm2. A positive value for the gain cross-sections has been found for a population inversion factor c of 0.4 in the spectral range from 1060 to 1110 nm. All these results suggest the potentially use of this system as a laser host

Experimental and theoretical study of α–Eu2(MoO4)3 under compression

The compression process in the α-phase of europium trimolybdate was revised employing several experimental techniques. X-ray diffraction (using synchrotron and laboratory radiation sources), Raman scattering and photoluminescence experiments were performed up to a maximum pressure of 21 GPa. In addition, the crystal structure and Raman mode frequencies have been studied by means of first-principles density functional based methods. Results suggest that the compression process of α-Eu2(MoO4)3 can be described by three stages. Below 8 GPa, the α-phase suffers an isotropic contraction of the crystal structure. Between 8 and 12 GPa, the compound undergoes an anisotropic compression due to distortion and rotation of the MoO4 tetrahedra. At pressures above 12 GPa, the amorphization process starts without any previous occurrence of a crystalline-crystalline phase transition in the whole range of pressure. This behavior clearly differs from the process of compression and amorphization in trimolybdates with β′-phase and tritungstates with α-phase.We thank Diamond Light Source for access to beamline I15 (EE1746) that contributed to the results presented here. Part of the diffraction measurements were performed at the 'Servicio Integrado de Difraccion de Rayos X (SIDIX)' of University of La Laguna. This work has been supported by Ministerio de Economia y Competitividad of Spain (MINECO) for the research projects through the National Program of Materials (MAT2010-21270-C04-01/02/03/04, MAT2013-46649-C41/2/3/4-P and MAT2013-43319-P), the Consolider-Ingenio 2010 MALTA (CSD2007-00045), the project of Generalitat Valenciana (GVA-ACOMP/2014/243) and by the European Union FEDER funds. C Guzman-Afonso wishes to thank ACIISI and FSE for a fellowship. J A Sans thanks the FPI and 'Juan de la Cierva' programs for fellowships.Guzmán-Afonso, C.; León-Luis, S.; Sans-Tresserras, JÁ.; González -Silgo, C.; Rodríguez-Hernández, P.; Radescu, S.;  muñoz, A.... (2015). Experimental and theoretical study of α–Eu2(MoO4)3 under compression. Journal of Physics: Condensed Matter. 27(46):465401-1-465401-11. https://doi.org/10.1088/0953-8984/27/46/465401S465401-1465401-11274

Pressure-induced amorphization of YVO4:Eu3+ nanoboxes

This is an author-created, un-copyedited version of an article published in Nanotechnology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0957-4484/27/2/025701A structural transformation from the zircon-type structure to an amorphous phase has been found in YVO4:Eu3+ nanoboxes at high pressures above 12.7 GPa by means of x-ray diffraction measurements. However, the pair distribution function of the high-pressure phase shows that the local structure of the amorphous phase is similar to the scheelite-type YVO4. These results are confirmed both by Raman spectroscopy and Eu3+ photoluminescence which detect the phase transition to a scheelite-type structure at 10.1 and 9.1 GPa, respectively. The irreversibility of the phase transition is observed with the three techniques after a maximum pressure in the upstroke of around 20 GPa. The existence of two D-5(0)-> F-7(0) photoluminescence peaks confirms the existence of two local environments for Eu3+, at least for the low-pressure phase. One environment is the expected for substituting Y3+ and the other is likely a disordered environment possibly found at the surface of the nanoboxes.This work has been performed under financial support from Spanish MINECO under the National Program of Materials (MAT2013-46649-C4-1/2/3/4-P) and the Consolider-Ingenio 2010 Program (MALTA CSD2007-00045). Funding by the Fundacion Caja Canarias (ENER-01) and the EU-FEDER funds is also acknowledged. JR-F thanks the Alexander von Humboldt Foundation for a postdoctoral fellowship and NS thanks the German Research Foundation (DFG) for financial support (Project RA2585/1-1). We acknowledge Diamond Light Source for time on beamline I15 under proposals EE3652 and EE6517. Parts of this research were carried out at the light source PETRA III at DESY (Hamburg), a member of the Helmholtz Association (HFG). We would like to thank H-P Liermann and W Morgenroth for assistance in using beamline P02.2.Ruiz Fuertes, J.; Gomis, O.; León Luis, SF.; Schrodt, N.; Manjón Herrera, FJ.; Ray, S.; Santamaría Pérez, D.... (2016). Pressure-induced amorphization of YVO4:Eu3+ nanoboxes. Nanotechnology. 27(2):025701-1-025701-8. https://doi.org/10.1088/0957-4484/27/2/025701S025701-1025701-8272Piot, L., Le Floch, S., Cornier, T., Daniele, S., & Machon, D. (2013). Amorphization in Nanoparticles. The Journal of Physical Chemistry C, 117(21), 11133-11140. doi:10.1021/jp401121cZhang, F. X., Wang, J. W., Lang, M., Zhang, J. M., Ewing, R. C., & Boatner, L. A. (2009). High-pressure phase transitions ofScPO4andYPO4. Physical Review B, 80(18). doi:10.1103/physrevb.80.184114Lacomba-Perales, R., Errandonea, D., Meng, Y., & Bettinelli, M. (2010). High-pressure stability and compressibility ofAPO4(A=La, Nd, Eu, Gd, Er, and Y) orthophosphates: An x-ray diffraction study using synchrotron radiation. Physical Review B, 81(6). doi:10.1103/physrevb.81.064113Yuan, H., Wang, K., Li, S., Tan, X., Li, Q., Yan, T., … Zou., B. (2012). Direct Zircon-to-Scheelite Structural Transformation in YPO4 and YPO4:Eu3+ Nanoparticles Under High Pressure. The Journal of Physical Chemistry C, 116(46), 24837-24844. doi:10.1021/jp3088995Mishra, A. K., Garg, N., Pandey, K. K., Shanavas, K. V., Tyagi, A. K., & Sharma, S. M. (2010). Zircon-monoclinic-scheelite transformation in nanocrystalline chromates. Physical Review B, 81(10). doi:10.1103/physrevb.81.104109Wang, L., Yang, W., Ding, Y., Ren, Y., Xiao, S., Liu, B., … Mao, H. (2010). Size-Dependent Amorphization of NanoscaleY2O3at High Pressure. Physical Review Letters, 105(9). doi:10.1103/physrevlett.105.095701Mukherjee, S., Kim, K., & Nair, S. (2007). Short, Highly Ordered, Single-Walled Mixed-Oxide Nanotubes Assemble from Amorphous Nanoparticles. Journal of the American Chemical Society, 129(21), 6820-6826. doi:10.1021/ja070124cŞopu, D., Albe, K., Ritter, Y., & Gleiter, H. (2009). From nanoglasses to bulk massive glasses. Applied Physics Letters, 94(19), 191911. doi:10.1063/1.3130209Ozawa, L., & Itoh, M. (2003). Cathode Ray Tube Phosphors. Chemical Reviews, 103(10), 3835-3856. doi:10.1021/cr0203490Zhu, Y., Xu, W., Zhang, H., Wang, W., Tong, L., Xu, S., … Song, H. (2012). Highly modified spontaneous emissions in YVO4:Eu3+ inverse opal and refractive index sensing application. Applied Physics Letters, 100(8), 081104. doi:10.1063/1.3688167Khan, A. F., Haranath, D., Yadav, R., Singh, S., Chawla, S., & Dutta, V. (2008). Controlled surface distribution and luminescence of YVO4:Eu3+ nanophosphor layers. Applied Physics Letters, 93(7), 073103. doi:10.1063/1.2973163Cho, Y.-S., & Huh, Y.-D. (2011). Preparation of Transparent Red-Emitting YVO4:Eu Nanophosphor Suspensions. Bulletin of the Korean Chemical Society, 32(1), 335-337. doi:10.5012/bkcs.2011.32.1.335Jayaraman, A., Kourouklis, G. A., Espinosa, G. P., Cooper, A. S., & Van Uitert, L. G. (1987). A high-pressure Raman study of yttrium vanadate (YVO4) and the pressure-induced transition from the zircon-type to the scheelite-type structure. Journal of Physics and Chemistry of Solids, 48(8), 755-759. doi:10.1016/0022-3697(87)90072-2Wang, X., Loa, I., Syassen, K., Hanfland, M., & Ferrand, B. (2004). Structural properties of the zircon- and scheelite-type phases ofYVO4at high pressure. Physical Review B, 70(6). doi:10.1103/physrevb.70.064109Manjón, F. J., Rodríguez-Hernández, P., Muñoz, A., Romero, A. H., Errandonea, D., & Syassen, K. (2010). Lattice dynamics ofYVO4at high pressures. Physical Review B, 81(7). doi:10.1103/physrevb.81.075202Boehler, R. (2006). New diamond cell for single-crystal x-ray diffraction. Review of Scientific Instruments, 77(11), 115103. doi:10.1063/1.2372734Mao, H. K., Xu, J., & Bell, P. M. (1986). Calibration of the ruby pressure gauge to 800 kbar under quasi-hydrostatic conditions. Journal of Geophysical Research, 91(B5), 4673. doi:10.1029/jb091ib05p04673Hammersley, A. P., Svensson, S. O., Hanfland, M., Fitch, A. N., & Hausermann, D. (1996). Two-dimensional detector software: From real detector to idealised image or two-theta scan. High Pressure Research, 14(4-6), 235-248. doi:10.1080/08957959608201408Holland, T. J. B., & Redfern, S. A. T. (1997). Unit cell refinement from powder diffraction data: the use of regression diagnostics. Mineralogical Magazine, 61(404), 65-77. doi:10.1180/minmag.1997.061.404.07Kraus, W., & Nolze, G. (1996). POWDER CELL – a program for the representation and manipulation of crystal structures and calculation of the resulting X-ray powder patterns. Journal of Applied Crystallography, 29(3), 301-303. doi:10.1107/s0021889895014920Toby, B. H. (2001). EXPGUI, a graphical user interface forGSAS. Journal of Applied Crystallography, 34(2), 210-213. doi:10.1107/s0021889801002242Qiu, X., Thompson, J. W., & Billinge, S. J. L. (2004). PDFgetX2: a GUI-driven program to obtain the pair distribution function from X-ray powder diffraction data. Journal of Applied Crystallography, 37(4), 678-678. doi:10.1107/s0021889804011744Chupas, P. J., Qiu, X., Hanson, J. C., Lee, P. L., Grey, C. P., & Billinge, S. J. L. (2003). Rapid-acquisition pair distribution function (RA-PDF) analysis. Journal of Applied Crystallography, 36(6), 1342-1347. doi:10.1107/s0021889803017564Farrow, C. L., Juhas, P., Liu, J. W., Bryndin, D., Božin, E. S., Bloch, J., … Billinge, S. J. L. (2007). PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals. Journal of Physics: Condensed Matter, 19(33), 335219. doi:10.1088/0953-8984/19/33/335219Trenque, I., Mornet, S., Duguet, E., & Gaudon, M. (2013). New Insights into Crystallite Size and Cell Parameters Correlation for ZnO Nanoparticles Obtained from Polyol-Mediated Synthesis. Inorganic Chemistry, 52(21), 12811-12817. doi:10.1021/ic402152fLangford, J. I., & Wilson, A. J. C. (1978). Scherrer after sixty years: A survey and some new results in the determination of crystallite size. Journal of Applied Crystallography, 11(2), 102-113. doi:10.1107/s0021889878012844Klotz, S., Chervin, J.-C., Munsch, P., & Le Marchand, G. (2009). Hydrostatic limits of 11 pressure transmitting media. Journal of Physics D: Applied Physics, 42(7), 075413. doi:10.1088/0022-3727/42/7/075413Jeong, I.-K., Proffen, T., Mohiuddin-Jacobs, F., & Billinge, S. J. L. (1999). Measuring Correlated Atomic Motion Using X-ray Diffraction. The Journal of Physical Chemistry A, 103(7), 921-924. doi:10.1021/jp9836978Frogley, M. D., Sly, J. L., & Dunstan, D. J. (1998). Pressure dependence of the direct band gap in tetrahedral semiconductors. Physical Review B, 58(19), 12579-12582. doi:10.1103/physrevb.58.12579Birch, F. (1978). Finite strain isotherm and velocities for single-crystal and polycrystalline NaCl at high pressures and 300°K. Journal of Geophysical Research, 83(B3), 1257. doi:10.1029/jb083ib03p01257Popescu, C., Sans, J. A., Errandonea, D., Segura, A., Villanueva, R., & Sapiña, F. (2014). Compressibility and Structural Stability of Nanocrystalline TiO2 Anatase Synthesized from Freeze-Dried Precursors. Inorganic Chemistry, 53(21), 11598-11603. doi:10.1021/ic501571uChen, G., Stump, N. A., Haire, R. G., Peterson, J. R., & Abraham, M. M. (1992). Pressure-induced phase transition in YVO4:Eu3+: A luminescence study at high pressure. Journal of Physics and Chemistry of Solids, 53(10), 1253-1257. doi:10.1016/0022-3697(92)90241-5Rivera-López, F., Martín, I. R., Da Silva, I., González-Silgo, C., Rodríguez-Mendoza, U. R., Lavín, V., … Fernández-Urban, J. (2006). Analysis of the Eu3+emission in a SrWO4laser matrix under pressure. High Pressure Research, 26(4), 355-359. doi:10.1080/08957950601105085Dieke, G. H., & Crosswhite, H. M. (1963). The Spectra of the Doubly and Triply Ionized Rare Earths. Applied Optics, 2(7), 675. doi:10.1364/ao.2.000675Lavı́n, V., Babu, P., Jayasankar, C. K., Martı́n, I. R., & Rodrı́guez, V. D. (2001). On the local structure of Eu3+ ions in oxyfluoride glasses. Comparison with fluoride and oxide glasses. The Journal of Chemical Physics, 115(23), 10935-10944. doi:10.1063/1.1420731Peacock, R. D. (s. f.). The intensities of lanthanide f ↔ f transitions. Rare Earths, 83-122. doi:10.1007/bfb0116556Oomen, E. W. J. L., & van Dongen, A. M. A. (1989). Europium (III) in oxide glasses. Journal of Non-Crystalline Solids, 111(2-3), 205-213. doi:10.1016/0022-3093(89)90282-2Song, H., Chen, B., Peng, H., & Zhang, J. (2002). Light-induced change of charge transfer band in nanocrystalline Y2O3:Eu3+. Applied Physics Letters, 81(10), 1776-1778. doi:10.1063/1.1501441Ray, S., León-Luis, S. F., Manjón, F. J., Mollar, M. A., Gomis, Ó., Rodríguez-Mendoza, U. R., … Lavín, V. (2014). Broadband, site selective and time resolved photoluminescence spectroscopic studies of finely size-modulated Y2O3:Eu3+ phosphors synthesized by a complex based precursor solution method. Current Applied Physics, 14(1), 72-81. doi:10.1016/j.cap.2013.07.02

Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review

Neutron Capture on the s-Process Branching Point 171^{171}Tm via Time-of-Flight and Activation

The neutron capture cross sections of several unstable nuclides acting as branching points in the s process are crucial for stellar nucleosynthesis studies. The unstable $^{171}$Tm(t$_{1/2}$=1.92 yr) is part of the branching around mass A∼170 but its neutron capture cross section as a function of the neutron energy is not known to date. In this work, following the production for the first time of more than 5 mg of $^{171}$Tm at the high-flux reactor Institut Laue-Langevin in France, a sample was produced at the Paul Scherrer Institute in Switzerland. Two complementary experiments were carried out at the neutron time-of-flight facility (n_TOF) at CERN in Switzerland and at the SARAF liquid lithium target facility at Soreq Nuclear Research Center in Israel by time of flight and activation, respectively. The result of the time-of-flight experiment consists of the first ever set of resonance parameters and the corresponding average resonance parameters, allowing us to make an estimation of the Maxwellian-averaged cross sections (MACS) by extrapolation. The activation measurement provides a direct and more precise measurement of the MACS at 30 keV: 384(40) mb, with which the estimation from the n_TOF data agree at the limit of 1 standard deviation. This value is 2.6 times lower than the JEFF-3.3 and ENDF/B-VIII evaluations, 25% lower than that of the Bao et al. compilation, and 1.6 times larger than the value recommended in the KADoNiS (v1) database, based on the only previous experiment. Our result affects the nucleosynthesis at the A∼170 branching, namely, the $^{171}$Yb abundance increases in the material lost by asymptotic giant branch stars, providing a better match to the available pre-solar SiC grain measurements compared to the calculations based on the current JEFF-3.3 model-based evaluation

Review and new concepts for neutron-capture measurements of astrophysical interest

The idea of slow-neutron capture nucleosynthesis formulated in 1957 triggered a tremendous experimental effort in different laboratories worldwide to measure the relevant nuclear physics input quantities, namely (n, γ) cross sections over the stellar temperature range (from few eV up to several hundred keV) for most of the isotopes involved from Fe up to Bi. A brief historical review focused on total energy detectors will be presented to illustrate how advances in instrumentation have led to the assessment of new aspects of s-process nucleosynthesis and to the progressive refinement of stellar models. A summary will be presented on current efforts to develop new detection concepts, such as the Total-Energy Detector with γ-ray imaging capability (i-TED). The latter is based on the simultaneous combination of Compton imaging with neutron time-of-flight (TOF) techniques, in order to achieve a superior level of sensitivity and selectivity in the measurement of stellar neutron capture rates.European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (ERC Consolidator Grant project HYMNS) 681740Instituto de Salud Carlos III Spanish Government FPA2014-52823-C2-1-P FPA2017-83946-C2-1-PConsejo Superior de Investigaciones Cientificas (CSIC) PIE-201750I26Program Severo Ochoa SEV-2014-039

Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

This article presents a few selected developments and future ideas related to the measurement of (n,γ) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with γ-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area

Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

This article presents a few selected developments and future ideas related to the measurement of (n,γ) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with γ-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area