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Dore L.,University of Bologna | Bizzocchi L.,CAAUL | Esposti C.D.,University of Bologna | Tamassia F.,University of Bologna
Molecular Physics | Year: 2011

The deuterated radical ND was produced in a DC discharge cell cooled at liquid nitrogen temperature. The discharge proved to be vibrationally hot, therefore the transient species could be detected in its vibrational excited states up to v=6. By scanning in the 431-531GHz frequency region, several fine-structure components of the N=1 → 0 transition in vibrational excited states were observed, each of them showing a complex hyperfine structure. A global analysis, including the measured frequencies and previous submillimetre-wave and infrared data, allowed an accurate determination of the equilibrium spectroscopic parameters of the ND radical including fine and hyperfine constants. A very precise determination of the equilibrium bond length r e was obtained. This value is not consistent with the value reported in the literature from NH data. This incongruity was discussed in terms of the breakdown of the Born-Oppenheimer approximation. In view of the recent detection of ND in a solar-mass protostar [A. Bacmann et al., Astron. Astrophys. 521, L42 (2010)], an extended spectroscopic characterization of this deuterated isotopologue of the NH species may prove useful, considering the large deuterium enhancement observed in molecular clouds. Copyright © 2011 Taylor and Francis Group, LLC.

Bizzocchi L.,CAAUL | Tamassia F.,University of Bologna | Esposti C.D.,University of Bologna | Fusina L.,University of Bologna | And 2 more authors.
Molecular Physics | Year: 2011

The infrared spectrum of diacetylene has been recorded at high resolution between 500 and 1000cm -1 by Fourier transform spectroscopy. More than 1200 transitions were assigned to five bands: the v 8 fundamental, the v 7+v 9 combination, and the v 3-v 9 difference bands as well as the most intense v 8+v 9-v 9 and v 7+2v 9-v 9 hot bands. The data were analysed together with the previously recorded millimetre-wave lines for the v 8-v 6 and v 8+v 9-(v 6+v 8) difference bands. Rotational and vibrational l-type resonances, together with the cubic anharmonic interactions which couple the v 3=1 stretching state with the v 8=v 9=1 combination and v 7=2 overtone states, have been considered in the least-squares fits to the observed wavenumbers in order to derive reliable spectroscopic parameters. The spectral analyses deliver very precise B 0 and D 0 parameters and experimental values of the anharmonicity constants for the bending-bending combination states of diacetylene below 1000cm -1. Copyright © 2011 Taylor and Francis Group, LLC.

Ultra Steep Spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z > 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here we present a first detailed analysis of the nature of the faintest USS sources. By using GMRT and VLA radio observations of the Lockman Hole (LH) at 610MHz and 1.4GHz, a sample of 58 micro-Jansky USS sources is assembled. Deep infrared data at 3.6 and 4.5μm from the Spitzer Extragalactic Representative Volume Survey (SERVS) is used to reliably identify counterparts for 48 (83%) of these sources, showing an average magnitude of [3.6]=19.7 mag(AB). Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z =0.1 to z=2.8, peaking at z∼0.6 and tailing off at high redshifts. © Springer-Verlag Berlin Heidelberg 2012.

Giuliano B.M.,University of Coimbra | Bizzocchi L.,CAAUL | Sanchez R.,University of Valladolid | Villanueva P.,University of Valladolid | And 3 more authors.
Journal of Chemical Physics | Year: 2011

The pure rotational spectra of 18 and 21 isotopic species of GeSe and GeTe have been measured in the frequency range 5-24GHz using a Fabry-Pérot- type resonator pulsed-jet Fourier-transform microwave spectrometer. Gaseous samples of both chalcogenides were prepared by a combined dc discharge/laser ablation technique and stabilized in supersonic jets of Ne. Global multi-isotopologue analyses of the derived rotational data, together with literature high-resolution infrared data, produced very precise Dunham parameters, as well as rotational constant Born-Oppenheimer breakdown (BOB) coefficients (δ01) for Ge, Se, and Te. A direct fit of the same datasets to an appropriate radial Hamiltonian yielded analytic potential-energy functions and BOB radial functions for the X1Σ+ electronic state of both GeSe and GeTe. Additionally, the electric quadrupole and magnetic hyperfine interactions produced by the nuclei 73Ge, 77Se, and 125Te were observed, yielding much improved quadrupole coupling constants and first determinations of the spin-rotation parameters. © 2011 American Institute of Physics.

Withers P.,Boston University | Fallows K.,Boston University | Girazian Z.,Boston University | Matta M.,Boston University | And 9 more authors.
Geophysical Research Letters | Year: 2012

[1] By examining electron density profiles from the Mars Express Radio Science Experiment MaRS, we show that the vertical structure of the dayside ionosphere of Mars is more variable and more complex than previously thought. The top of the ionosphere can be below 250 km (25% occurrence rate) or above 650 km (1%); the topside ionosphere can be well-described by a single scale height (10%) or two/three regions with distinct scale heights (25% or 10%), where those scale heights range between tens and hundreds of kilometers; the main layer of the ionosphere can have a sharply pointed (5%), flat-topped (6%), or wavy (8%) shape, in contrast to its usual Chapman-like shape; a broad increase in electron density is detected at 160-180 km (10%); a narrow increase in electron density is sometimes found in strongly-magnetized regions; and an additional layer is present between the M1 and M2 layers (3%). © 2012. American Geophysical Union. All Rights Reserved.

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