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Molecular Rings (molecular + ring)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Molecular Magnets: Deposition of Functionalized Cr7Ni Molecular Rings on Graphite from the Liquid Phase (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
Mater.
[source]

Deposition of Functionalized Cr7Ni Molecular Rings on Graphite from the Liquid Phase

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
Alberto Ghirri
Abstract Graphite is a clean substrate and its nanostructures hold great potential for applications. Anchoring large molecules on graphite represents a challenge for several reasons that essentially rise from the planar bonds of the packed honeycomb structure of carbon. Here, a systematic investigation by AFM and XPS on different derivatives of molecular Cr7Ni rings deposited on highly oriented pyrolytic graphite (HOPG) is reported. Cr7Ni is emerging as a prototipical example of molecular antiferromagnet on which quantum phenomena and coherence have been demonstrated. For the deposition of Cr7Ni on HOPG, two strategies are adopted: 1) Cr7Ni rings are functionalized with extended alkyl/benzene terminations and 2) a self-assembled monolayer of alkyl chains with sulfonate terminations is deposited and then a cationic Cr7Ni derivative is used. In both cases the electronic bond with the carbon surface is soft, but the two-step procedure is efficient, albeit indirect, in sticking molecular Cr7Ni on HOPG. These strategies can be easily extended to deposit other complex molecular aggregates on graphite from the liquid phase. [source]

A deep kinematic survey of planetary nebulae in the Andromeda galaxy using the Planetary Nebula Spectrograph

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006
H. R. Merrett
ABSTRACT We present a catalogue of positions, magnitudes and velocities for 3300 emission-line objects found by the Planetary Nebula Spectrograph in a survey of the Andromeda galaxy, M31. Of these objects, 2615 are found likely to be planetary nebulae (PNe) associated with M31. The survey area covers the whole of M31's disc out to a radius of . Beyond this radius, observations have been made along the major and minor axes, and the Northern Spur and Southern Stream regions. The calibrated data have been checked for internal consistency and compared with other catalogues. With the exception of the very central, high surface brightness region of M31, this survey is complete to a magnitude limit of m5007, 23.75, 3.5 mag into the PN luminosity function. We have identified emission-line objects associated with M31's satellites and other background galaxies. We have examined the data from the region tentatively identified as a new satellite galaxy, Andromeda VIII, comparing it to data in the other quadrants of the galaxy. We find that the PNe in this region have velocities that appear to be consistent with membership of M31 itself. The luminosity function of the surveyed PNe is well matched to the usual smooth monotonic function. The only significant spatial variation in the luminosity function occurs in the vicinity of M31's molecular ring, where the luminosities of PNe on the near side of the galaxy are systematically ,0.2 mag fainter than those on the far side. This difference can be explained naturally by a modest amount of obscuration by the ring. The absence of any difference in luminosity function between bulge and disc suggests that the sample of PNe is not strongly populated by objects whose progenitors are more massive stars. This conclusion is reinforced by the excellent agreement between the number counts of PNe and the R -band light. The number counts of kinematically selected PNe also allow us to probe the stellar distribution in M31 down to very faint limits. There is no indication of a cut-off in M31's disc out to beyond four scalelengths, and no signs of a spheroidal halo population in excess of the bulge out to 10 effective bulge radii. We have also carried out a preliminary analysis of the kinematics of the surveyed PNe. The mean streaming velocity of the M31 disc PNe is found to show a significant asymmetric drift out to large radii. Their velocity dispersion, although initially declining with radius, flattens out to a constant value in the outer parts of the galaxy. There are no indications that the disc velocity dispersion varies with PN luminosity, once again implying that the progenitors of PNe of all magnitudes form a relatively homogeneous old population. The dispersion profile and asymmetric drift results are shown to be mutually consistent, but require that the disc flares with radius if the shape of its velocity ellipsoid remains invariant. [source]

The magnetic field in the central parsec

ASTRONOMISCHE NACHRICHTEN, Issue S1 2003
A. C. H. Glasse
Abstract We present imaging polarimetry of Sgr A at a wavelength of 12.5 ,m, obtained with Michelle on UKIRT early in 2002. With considerably more sensitivity than previously available we have concentrated on the faint region bounded by the northern arm north of IRS1, IRS8, and the western arc of the molecular ring, to probe the magnetic field directions in this region. [source]