2,985 research outputs found
Strong polarization of the residual nucleus in a heavy-ion induced transfer reaction
A strong polarization of 20Ne levels has been observed in the 16O(16O, 12C)20Ne* reaction along an axis perpendicular to the reaction plane. This polarization differs from that reported in the (7Li, t) reaction, when the same nuclear levels were populated. D.W.B.A. calculations which fitted both angular distributions and polarization in the (7Li, t) reaction and which can also describe the (16O, 12C) angular distributions fail to reproduce the associated 20Ne* polarization
Excited states of 19N and 21O
(18O, 19N) and (18O, 21O) nuclear reactions on a 18O target provide measurements of excited state energies at 1.12 and 1.59 MeV for 19N and at 1.35 and 3.00 MeV for 21O. The 19N mass is remeasured as 15.856 ± 0.050 MeV
Application of the Frobenius method to the Schrodinger equation for a spherically symmetric potential: anharmonic oscillator
The power series method has been adapted to compute the spectrum of the
Schrodinger equation for central potential of the form . The bound-state energies
are given as zeros of a calculable function, if the potential is confined in a
spherical box. For an unconfined potential the interval bounding the energy
eigenvalues can be determined in a similar way with an arbitrarily chosen
precision. The very accurate results for various spherically symmetric
anharmonic potentials are presented.Comment: 16 pages, 5 figures, published in J. Phys
Spin-dependent charge transfer at chiral electrodes probed by magnetic resonance
Chirality-induced spin selectivity is evidenced by exciting the spin resonance of radicals in an electrochemical cell where the working electrode is covered with a chiral self-assembled monolayer. Because the electron transfer to and from the paramagnetic radical is spin dependent, the electrochemical current changes at resonance. This electrically-detected magnetic resonance (EDMR) is monitored by a lock-in detection based on electrode voltage modulation, at a frequency that optimizes the sensitivity of the differential conductance to the electrode charge transfer process. The method is validated using p-doped GaAs electrodes in which the conduction band electrons are hyperpolarized by a well-known method of optical spin pumping with circularly polarized light. Gold electrodes covered with peptides consisting of 5 alanine groups (Al5) present a relative current change of up to 5 × 10-5 when the resonance condition is met, corresponding to a spin filtering efficiency between 6 and 19%
Spectroscopy of F
The structure of the weakly-bound F odd-odd nucleus,
produced from Na nuclei, has been investigated at GANIL by means of
the in-beam -ray spectroscopy technique. A single -line is
observed at 657(7) keV in F which has been ascribed to the decay of
the excited J= state to the J=1 ground state. The possible presence of
intruder negative parity states in F is also discussed.Comment: 3 pages, 1 figure, accepted for publication in Physical Review
Dissecting the origin of the submillimeter emission in nearby galaxies with Herschel and LABOCA
We model the infrared to submillimeter spectral energy distribution of 11
nearby galaxies of the KINGFISH sample using Spitzer and Herschel data and
compare model extrapolations at 870um (using different fitting techniques) with
LABOCA 870um observations. We investigate how the differences between
predictions and observations vary with model assumptions or environment. At
global scales, we find that modified blackbody models using realistic cold
emissivity indices (beta_c=2 or 1.5) are able to reproduce the 870um observed
emission within the uncertainties for most of the sample. Low values
(beta_c<1.3) would be required in NGC0337, NGC1512 and NGC7793. At local
scales, we observe a systematic 870um excess when using beta_=2.0. The
beta_c=1.5 or the Draine and Li (2007) models can reconcile predictions with
observations in part of the disks. Some of the remaining excesses occur towards
the centres and can be partly or fully accounted for by non-dust contributions
such as CO(3-2) or, to a lesser extent, free-free or synchrotron emission. In
three non-barred galaxies, the remaining excesses rather occur in the disk
outskirts. This could be a sign of a flattening of the submm slope (and
decrease of the effective emissivity index) with radius in these objects.Comment: 31 pages (including appendix), 7 figures, accepted for publication in
MNRA
Extinction law variations and dust excitation in the spiral galaxy NGC 300
We investigate the origin of the strong radial gradient in the
ultraviolet-to-infrared ratio in the spiral galaxy NGC 300, and emphasize the
importance of local variations in the interstellar medium geometry, concluding
that they cannot be neglected with respect to metallicity effects. This
analysis is based upon a combination of maps from GALEX and Spitzer, and from
the ground (UBVRI, Halpha and Hbeta). We select ionizing stellar clusters
associated with HII regions of widely varying morphologies, and derive their
fundamental parameters from population synthesis fitting of their spectral
energy distributions, measured to eliminate local backgrounds accurately. From
these fits, we conclude that the stellar extinction law is highly variable in
the line of sight of young clusters of similar ages. In the particular model
geometry that we consider most appropriate to the sampled regions, we checked
that our findings are not significantly altered by the correct treatment of
radiative transfer effects. The variations are systematic in nature: extinction
laws of the Milky Way or LMC type are associated with compact HII regions (the
compacity being quantified in two different ways), while clusters surrounded by
diffuse HII regions follow extinction laws of the 30 Doradus or SMC type. The
Calzetti starburst attenuation law, although most often degenerate with the 30
Doradus extinction law, overpredicts ionizing photon fluxes by large amounts.
We also find that the extinction law variations are correlated with the column
density of dust species emitting in the near- and mid-infrared. Finally, we
briefly discuss the nebular to stellar extinction ratios, and the excitation of
aromatic band carriers, invalidating their claimed association with cold dust.Comment: accepted for publication in ApJ -- figure 6 abridged her
Herschel and JCMT observations of the early-type dwarf galaxy NGC 205
We present Herschel dust continuum, James Clerk Maxwell Telescope CO(3-2)
observations and a search for [CII] 158 micron and [OI] 63 micron spectral line
emission for the brightest early-type dwarf satellite of Andromeda, NGC 205.
While direct gas measurements (Mgas ~ 1.5e+6 Msun, HI + CO(1-0)) have proven to
be inconsistent with theoretical predictions of the current gas reservoir in
NGC 205 (> 1e+7 Msun), we revise the missing interstellar medium mass problem
based on new gas mass estimates (CO(3-2), [CII], [OI]) and indirect
measurements of the interstellar medium content through dust continuum
emission. Based on Herschel observations, covering a wide wavelength range from
70 to 500 micron, we are able to probe the entire dust content in NGC 205
(Mdust ~ 1.1-1.8e+4 Msun at Tdust ~ 18-22 K) and rule out the presence of a
massive cold dust component (Mdust ~ 5e+5 Msun, Tdust ~ 12 K), which was
suggested based on millimeter observations from the inner 18.4 arcsec. Assuming
a reasonable gas-to-dust ratio of ~ 400, the dust mass in NGC 205 translates
into a gas mass Mgas ~ 4-7e+6 Msun. The non-detection of [OI] and the low
L_[CII]-to-L_CO(1-0) line intensity ratio (~ 1850) imply that the molecular gas
phase is well traced by CO molecules in NGC 205. We estimate an atomic gas mass
of 1.5e+4 Msun associated with the [CII] emitting PDR regions in NGC 205. From
the partial CO(3-2) map of the northern region in NGC 205, we derive a
molecular gas mass of M_H2 ~ 1.3e+5 Msun. [abridged]Comment: 16 pages, 7 figures, accepted for publication in MNRA
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