The contribution of CHONS particles to the diffuse high-Galactic-latitude IR emission

Papoular, R.

doi:10.1093/mnras/stu323

Cited by 4 publications

(2 citation statements)

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“…The seduction of the coal model of UIE and the related petroleum fraction and asphaltene models which at the end can be collected into the more general MAONs model regards the fact that it does not exist a single reference spectrum but samples of both coal, petroleum fractions and asphaltenes can be selected at different degrees of "maturity" or ranks. It is possible, for instance, to start from a low rank coal that is richer in hydrogen content and aliphatics and by a thermal or radiation treatment reach a higher rank coal with lower hydrogen content and higher aromatic content (Papoular, 2013(Papoular, , 2014Cataldo & Keheyan, 2003;Cataldo, Keheyan & Baccaro, 2004). In parallel, also the organic matter in space -for example, as found around evolved stars such as asymptotic giant branch (AGB) stars and (proto-)planetary nebulae -responsible for the UIE undergoes a considerable evolution since its mixed aliphatic/aromatic ratio changes continuously, affecting the resulting UIE features.…”

Section: -Carbonization Of Selected Substrates To Match the Anthracit...mentioning

confidence: 99%

“…Through spectral fittings of the astronomical spectra of the UIE, Kwok & Zhang (2011) have shown that a significant amount of the energy is emitted by the aliphatic component, implying that aliphatic groups are an essential part of the chemical structure. The MAON concept was also explored further by Papoular (2013Papoular ( , 2014. In the context of the petroleum fractions, and have shown that examples of naturally occurring MAONs can be represented by petroleum asphaltenes as well as asphaltenes derived by other fossil hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

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Petroleum, coal and other organics in space

Cataldo¹,

García–Hernández²,

Manchado³

2020

Astrophys Space Sci

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The petroleum and coal models of the unidentified infrared emissions (UIE), sometimes referred also as unidentified infrared bands (UIBs) has been reviewed mainly based on the work of the authors with the inclusion of unpublished results. It is shown that the petroleum and coal model of the UIE converges and merges quite well with the MAON (Mixed Aromatic Aliphatic Organic Nanoparticles) model of the UIE. It is shown that the thermal treatment of various substrates like PAHs, alkylated PAHs but also mixed aliphatic/olefinic substrates leads invariable to carbonaceous materials matching the infrared spectrum of anthracite coal or certain petroleum fractions. Thus, the experimental thermal processing (which under space conditions could be equivalent to the expected processing by shock waves or high energy radiation) of mixed aromatic/aliphatic organic matter can be used to match also the UIE evolution. Another way to simulate the thermal/radiation processing of organic matter in space, can be achieved through the carbon arc. Simple substrates processed in this way produce carbon soot and a plethora of organic molecules. Fullerenes are found in space both through mid-infrared and optical spectroscopy and it is very likely that other complex related species such as endohedral fullerenes (i.e. fullerenes with a metal, heteroatom or molecules inside the cage) may be formed in space. After all, their formation requires the same conditions as those needed for fullerene formation provided that also a metal vapour (e.g. interstellar/circumstellar gas) is available. The last part of this review is thus dedicated to the recent results on the study and characterization of an endohedral C60 derivative containing lithium inside the cage.

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Section: -Carbonization Of Selected Substrates To Match the Anthracit...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Petroleum, coal and other organics in space

Cataldo¹,

García–Hernández²,

Manchado³

2020

Astrophys Space Sci

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Molecular phonons and their absorption/emission spectra from the far-IR to microwaves

Papoular¹

2015

Monthly Notices of the Royal Astronomical Society

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Together with their fingerprint modes, molecules carry coherent vibrations of all their atoms (phonons). Phonon spectra extend from ∼20 to more than 10 4 µm, depending on molecular size. These spectra are discrete but large assemblies of molecules of the same family, differing only by minor structural details, will produce continua. As such assemblies are expected to exist in regions where dust accumulates, they are bound to contribute to the observed continua underlying the Unidentified Infrared Bands and the 21-µm band of planetary nebulae as well as to the diffuse galactic emission surveyed by the Planck astronomical satellite and other means. The purpose of this work is to determine, for carbon-rich molecules, the intensity of such continua and their extent into the millimetric range, and to evaluate their detectability in this range. The rules governing the spectral distributions of phonons are derived and shown to differ from those which obtain in the solid state. Their application allow the extinction cross-section per H atom, and its maximum wavelength, to be determined as a function of molecular size and dimensionality. Chemical modeling of more than 15 large molecules illustrate these results. It is found that the maximum phonon wavelength of a 2D structure increases roughly as the square of its larger dimension. Spectral energy distributions were computed as far as 4000 µm, for molecules up to 50Å in length.

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On interstellar light polarization by diamagnetic silicate and carbon dust in the infrared

Papoular

2018

Monthly Notices of the Royal Astronomical Society

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The motion of diamagnetic dust particles in interstellar magnetic fields is studied numerically with several different sets of parameters. Two types of behavior are observed, depending on the value of the critical number R, which is a function of the grain inertia, the magnetic susceptibility of the material and of the strength of rotation braking. If R ≤ 10, the grain ends up in a static state and perfectly aligned with the magnetic field, after a few braking times. If not, it goes on precessing and nutating about the field vector for a much longer time. Usual parameters are such that the first situation can hardly be observed. Fortunately, in the second and more likely situation, there remains a persistent partial alignment which is far from negligible, although it decreases as the field decreases and as R increases. The solution of the complete equations of motion of grains in a field helps understanding the details of this behavior. One particular case of an ellipsoidal forsterite silicate grain is studied in detail and shown to polarize light in agreement with astronomical measurements of absolute polarization in the infrared. Phonons are shown to contribute to the progressive flattening of extinction and polarization towards long wavelengths. The measured dielectric properties of forsterite qualitatively fit the Serkowski peak in the visible.

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The contribution of CHONS particles to the diffuse high-Galactic-latitude IR emission

Cited by 4 publications

References 31 publications

Petroleum, coal and other organics in space

Petroleum, coal and other organics in space

Molecular phonons and their absorption/emission spectra from the far-IR to microwaves

On interstellar light polarization by diamagnetic silicate and carbon dust in the infrared

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