scholarly journals The Charge State of Polycyclic Aromatic Hydrocarbons across a Reflection Nebula, an H ii Region, and a Planetary Nebula

2018 ◽  
Vol 858 (2) ◽  
pp. 67 ◽  
Author(s):  
C. Boersma ◽  
J. Bregman ◽  
L. J. Allamandola
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Charge State ◽  
Aromatic Hydrocarbons ◽  
Planetary Nebula ◽  
Reflection Nebula ◽  
Polycyclic Aromatic ◽  
H Ii Region

scholarly journals An infrared study of Roberts 22

1997 ◽  
Vol 180 ◽  
pp. 361-361 ◽  
Author(s):  
F.J. Molster ◽  
L.B.F.M. Waters ◽  
T. de Jong ◽  
T. Prusti ◽  
A. Zijlstra ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Spectral Type ◽  
Aromatic Hydrocarbons ◽  
Planetary Nebula ◽  
Central Star ◽  
Peculiar Star ◽  
Infrared Study ◽  
Polycyclic Aromatic ◽  
Rich Material

Roberts 22 (= AFGL 4104) is a peculiar proto-planetary nebula. Its central star has spectral type A2Ie. An OH maser was detected by Manchester et al. (1969), indicating that the shell is oxygen-rich. However Polycyclic Aromatic Hydrocarbons (PAH) features were observed as well (Allen et al., 1982; Cohen et al., 1993), indicating that carbon rich material is also present. In this poster we present new IR data (images and spectra) of this peculiar star and propose an explanation for this curious behaviour.

scholarly journals Various Aspects of the Spectroscopy of PAHs (Polycyclic Aromatic Hydrocarbons)

2002 ◽  
Vol 12 ◽  
pp. 44-47
Author(s):  
Philippe Bréchignac
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Charge State ◽  
Aromatic Hydrocarbons ◽  
Near Infrared ◽  
Spectroscopic Properties ◽  
Infrared Emission ◽  
Ir Absorption ◽  
Near Ir ◽  
Polycyclic Aromatic ◽  
Infrared Intensities

AbstractThe exploitation of the recent observations (in particular by ISO) of the near infrared emission bands (UIBs) requires a good knowledge of the spectroscopic properties of the main proposed carriers, i.e. the Polycyclic Aromatic Hydrocarbons, which are expected to act as efficient UV/visible to infrared free-flying light converters.The charge state of the interstellar PAHs strongly affects their spectroscopy. The laboratory study of the electronic transitions of PAH cations in the gas phase enables to address important questions, like their possible contribution to the Diffuse Interstellar Bands (visible and near-IR absorption), and the mechanism responsible for electronic to vibrational intramolecular energy conversion.Microcanonical simulations based on hybrid quantum/classical theoretical methods reveal how strongly affected are the infrared intensities by both the charge state and the vibrational temperature.

scholarly journals Silicate and ice emission bands in the ISO spectrum of the PAH-emitting carbon-rich planetary nebula CPD-56°8032

1999 ◽  
Vol 191 ◽  
pp. 291-296
Author(s):  
Martin Cohen ◽  
M. J. Barlow ◽  
R. J. Sylvester ◽  
X.-W. Liu ◽  
P. Cox ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Planetary Nebula ◽  
Kuiper Belt ◽  
Simultaneous Presence ◽  
Water Ice ◽  
Polycyclic Aromatic ◽  
Crystalline Water ◽  
History Of ◽  
Bright Emission

Combined ISO SWS and LWS spectroscopy is presented of the late WC-type planetary nebula nucleus CPD-56†8032 and its carbon-rich nebula. The extremely broad coverage (2.4–197 μm) enables us to recognize the clear and simultaneous presence of emission features from both oxygen- and carbon-rich circumstellar materials. Removing a smooth continuum highlights bright emission bands characteristic of polycyclic aromatic hydrocarbons (hereafter PAHs) in the 3–15 μm region, bands from crystalline silicates longwards of 18 μm, and the 43- and 62-μm bands of crystalline water ice. We discuss the probable evolutionary state and history of this unusual object in terms of (a) a recent transition from an O-rich to a C-rich outflow following a helium shell flash; or (b) a carbon-rich nebular outflow encountering an O-rich comet cloud orbiting in a Kuiper-belt-like distribution.

The Assessment of Contamination and Source of Polycyclic Aromatic Hydrocarbons from the Sediments of the Someş River

2019 ◽  
Vol 64 (1) ◽  
pp. 55-67
Author(s):  
Vlad Pӑnescu ◽  
◽  
Mihaela Cӑtӑlina Herghelegiu ◽  
Sorin Pop ◽  
Mircea Anton ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Polycyclic Aromatic

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

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