CaH Rydberg Series, Oscillator Strengths and Photoionization Cross Sections from Molecular Quantum Defect and Dyson Orbital Theories

Producción CientíficaIn this work, electron-propagator methods are applied to the calculation of the ionization potential and vertical excitation energies for several Rydberg series of the CaH molecule. The present calculations cover more highly excited states than those previously reported. In particular, excitation energies for ns (n>5), np (n>5), nd (n>4) and nf Rydberg states are given. Oscillator strengths for electronic transitions involving Rydberg states of CaH, as well as photoionization cross sections for Rydberg channels, also have been determined by using the Molecular Quantum Defect Orbital approach. Good agreement has been found with the scarce comparative data that are available for oscillator strengths. To our knowledge, predictions of photoionization cross sections from the outermost orbital of CaH are made here for the first time. A Cooper minimum and mixed atomic orbital character in some of the Dyson orbitals are among the novel features of these present calculationsJunta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA330U13

Excitation energies, photoionization cross sections, and asymmetry parameters of the methyl and silyl radicals

Producción CientíficaVertical excitation energies of the methyl and silyl radicals were inferred from ab initio electron propagator calculations on the electron affinities of CH3 + and SiH3 +. Photoionization cross sections and angular distribution of photoelectrons for the outermost orbitals of both CH3 and SiH3 radicals have been obtained with the Molecular Quantum Defect Orbital method. The individual ionization cross sections corresponding to the Rydberg channels to which the excitation of the ground state’s outermost electron gives rise are reported. Despite the relevance of methyl radical in atmospheric chemistry and combustion processes, only data for the photon energy range of 10–11 eV seem to be available. Good agreement has been found with experiment for photoionization cross section of this radical. To our knowledge, predictions of the above mentioned photoionization parameters on silyl radical are made here for the first time, and we are not aware of any reported experimental measurements. An analysis of our results reveals the presence of a Cooper minimum in the photoionization of the silyl radical. The adequacy of the two theoretical procedures employed in the present work is discussed.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA330U13

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

Streptococcus porcorum sp. nov., isolated from domestic and wild pigs

Seven isolates of an unidentified Gram-stain-positive, catalase-negative, coccus-shaped organism isolated from domestic and wild pigs were characterized by phenotypic and molecular-genetic methods. Based on cellular morphology and biochemical criteria, the isolates were tentatively assigned to the genus Streptococcus, although the organisms did not appear to correspond to any recognized species. Comparative 16S rRNA gene sequencing showed that the unknown bacterium was phylogenetically closely related to, but distinct from, Streptococcus suis (97.5 % 16S rRNA gene sequence similarity to the type strain). rpoB and sodA sequence analysis showed minimum interspecies divergence from phylogenetically close 16S rRNA gene sequence-based relatives of 13.8 and 18.6 %, respectively. DNA-DNA hybridization of a strain of the unidentified organism demonstrated 8-18 % reassociation with S. suis NCTC 10234(T). The novel bacterium could be distinguished from S. suis and other Streptococcus species using biochemical tests. On the basis of phenotypic and phylogenetic evidence, it is proposed that the unknown isolates from domestic and wild animals be assigned to a novel species of the genus Streptococcus, Streptococcus porcorum sp. nov. The type strain is 682-03(T) (= CCUG 58479(T) = CECT 7593(T))

Optical nanothermometer based on the calibration of the Stokes and upconverted green emissions of Er3+ ions in Y3Ga5O12 nano-garnets

The temperature-dependent green luminescence of Y3Ga5O12 nano-garnets doped with different concentrations of Er3+ ions has been measured from 300 to 850 K and, in more detail, in the biological range from 292 to 335 K. The green emissions were obtained by excitation under 488 nm blue or 800 nm near-infrared laser radiations. Both excitations give rise to bright green luminescence that can be seen by the naked eye, and which can be associated either with Stokes processes, i.e. multiphonon relaxations followed by green spontaneous emission, in the former case or with infrared-to-visible upconversion processes in the latter. The temperature-induced changes in the Er3+ green emissions have been calibrated for both excitations and results point to a strong dependence on the concentration of optically active Er3+ ions. The maximum value of the thermal sensitivity, 64 × 10−4 K−1 at 547 K, has been obtained for the nano-garnets doped with the lowest concentration of Er3+ ions, which is one of the highest values found in the literature. These results allow to conclude that a relatively low concentration of optically active ions is advisable and the changes induced by temperature on the green emissions are independent of the laser excitation radiation used, which is necessary to calibrate the temperature of the immediate environment of the Er3+-doped Y3Ga5O12 nano-garnets.This work have been partially supported by Ministerio de Economía y Competitividad de España (MINECO) under The National Program of Materials (MAT2010-21270-C04-02/-03, and MAT2013-46649-C4-3-P/-4-P), The Consolider-Ingenio 2010 Program (MALTA CSD2007-00045), and the Indo- Spanish Joint Programme of Cooperation in Science and Technology (PRI-PIBIN-2011-1153/DST-INT-Spain-P-38-11), and by the EU-FEDER funds. V. Venkatramu is also grateful to Council of Scientific and Industrial Research (CSIR), New Delhi for the sanction of major research project (No. 03(1229)/12/EMR-II, dated: 16th April, 2012). V. Monteseguro wishes to thank MICINN for the FPI grant (BES-2011- 044596)

Highly fluorinated erbium(III) complexes for emission in the C-band

Two highly fluorinated Er3+ complexes with three 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate (fod) groups and either bipyridine (bipy) or bathophenantholine (bath) as the ancillary ligand emitting at the C-band (third communication window for fiber transmission) are presented. These complexes are the result of a design process aimed at decreasing the vibrational quenching from high frequency oscillators. The structure of [Er(fod)3(bipy)] has been elucidated by single-crystal X-ray diffraction, while Sparkle/PM6 and Sparkle/PM7 semi-empirical calculations have been used to model the ground state geometry for [Er(fod)3(bath)]. Photoluminescence studies confirm sensitization of the Er3+ ions by antenna effect, leading to NIR emission at 1.53 μm. This energy transfer proves to be more efficient for [Er(fod)3(bath)] as a result of the bulkier and more rigid structure of bath diimide. The good thermal stability of the materials up to over 200 °C allows envisaging their use in erbium-doped waveguides, NIR-OLEDs or other optoelectronic devices

An erbium(III)-based NIR emitter with a highly conjugated ß-diketonate for blue-region sensitization

The sensitization of lanthanide complexes in the visible region is of particular interest for practical applications such as labeling, biological analysis and optoelectronics. A visible-light sensitized Er3+complex based on the use of a highly conjugated ß-diketonate (1, 3-di(2-naphthyl)-1, 3-propanedione, Hdnm) and 5-nitro-1, 10-phenanthroline (5NO2phen) as an ancillary ligand, [Er(dnm)3(5NO2phen)], has been synthesized, fully characterized and its photophysical properties have been investigated. Suitably expanded p-conjugation in the complex molecule makes the excitation window red-shifted to the visible region (up to 550 nm). Efficient energy transfer by antenna effect results in 1.53 µm emission from the Er3+ion

Electronic and elastic properties of yttrium gallium garnet under pressure from ab initio studies

In this paper, we present an ab initio study within the framework of density functional theory employing the generalized gradient approximation applied to the study of the structural, elastic, and electronic properties of yttrium gallium garnet, Y3Ga5O12, under hydrostatic pressure. The calculated structural ground state properties are in good agreement with the available experimental data. Pressure dependence of the elastic constants and the mechanical stability are analysed up to 90 GPa, showing that the garnet is mechanically unstable above 84 GPa. We also present the electronic band structure calculations which show that upon compression the fundamental direct gap first increases up to 63 GPa and later monotonically decreases under pressure. (C) 2013 AIP Publishing LLC.This work has been supported by Ministerio de Ciencia e Innovacion of Spain (MICINN) under the National Program of Materials (MAT2010-21270-C04-02/03/04) and the Consolider-Ingenio 2010 Program (MALTA CSD2007-0045), by the Vicerrectorado de Investigacion y Desarrollo of the Universitat Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11) and by the EU-FEDER funds. V. Monteseguro wishes to thank MICINN for the FPI Grant (BES-2011-044596). We thank the computer time provided by the Red Espanola de Supercomputacion (RES).Monteseguro, V.; Rodríguez-Hernández, P.; Lavín, V.; Manjón Herrera, FJ.; Muñoz, A. (2013). Electronic and elastic properties of yttrium gallium garnet under pressure from ab initio studies. Journal of Applied Physics. 113(18):183505-1-183505-8. https://doi.org/10.1063/1.4804133S183505-1183505-81131

Excitation of emission lines by fluorescence and recombination in IC 418

We predict intensities of lines of CII, NI, NII, OI and OII and compare them with a deep spectroscopic survey of IC 418 to test the effect of excitation of nebular emission lines by continuum fluorescence of starlight. Our calculations use a nebular model and a synthetic spectrum of its central star to take into account excitation of the lines by continuum fluorescence and recombination. The NII spectrum is mostly produced by fluorescence due to the low excitation conditions of the nebula, but many CII and OII lines have more excitation by fluorescence than recombination. In the neutral envelope, the NI permitted lines are excited by fluorescence, and almost all the OI lines are excited by recombination. Electron excitation produces the forbidden optical lines of OI, but continuum fluorescence excites most of the NI forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the photodissociation region of a nebula.Comment: 2 pages, 4 figures, to appear in proceedings of the IAU Symposium 283: "Planetary Nebulae: An Eye to the Future", Eds.: A. Manchado, L. Stanghellini and D. Schoenberne