Polycyclic Aromatic Hydrocarbons as a Source for 
	   (N = 4–6) and C<sub>3</sub>H<sub>2</sub> in the Interstellar Medium

Chacko, Roby; Banhatti, Shreyak; Barik, Saroj; Aravind, G.

doi:10.3847/1538-4357/ab8fb1

Cited by 8 publications

(5 citation statements)

References 85 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The photoionization and dissociation of anthracene C 14 H 10 (25.58 Å 3 ), phenanthrene C 14 H 10 (24.28 Å 3 ), and pentacene C 22 H 14 (49.24 Å 3 ) in the multiphoton regime at 266 nm wavelength is well-rationalized in terms of minimum polarizability (the mean polarizabilities calculated with the PBE/Λ22m method are shown in parentheses). Using mass-spectrometry, the authors analyzed the fragmentation ions, formed under irradiation, and found that phenanthrene was more survivable. They concluded about the higher stability of nonlinear PAHs compared to their linear isomers against UV irradiation due to the lower mean polarizability of kinked isomers.…”

Section: Astrochemical Applications Of Polarizabilitymentioning

confidence: 88%

Polarizability in Astrochemical Studies of Complex Carbon-Based Compounds

Sabirov,

Tukhbatullina,

Shepelevich

2022

ACS Earth Space Chem.

View full text Add to dashboard Cite

This Review summarizes the grounds and applications of polarizability to the astrochemical studies on carbon-based compounds, including polycyclic aromatic hydrocarbons and fullerenes. Polarizability is useful for the analysis of physicochemical processes (interactions with positrons, molecular collisions, quenching, and dielectric screening) and chemical reactions. The idea of a combined use of minimum-polarizability and minimum-energy principles for searching for novel candidates for interstellar/circumstellar detection is considered. Insights into the astrochemistry of fullerenes and helicenes coming from their polarizability are discussed.

show abstract

Section: Astrochemical Applications Of Polarizabilitymentioning

confidence: 88%

Polarizability in Astrochemical Studies of Complex Carbon-Based Compounds

Sabirov,

Tukhbatullina,

Shepelevich

2022

ACS Earth Space Chem.

View full text Add to dashboard Cite

show abstract

“…The added proton easily jumps from one carbon atom to another in the molecule and ethylene is only ejected when the proton is bonded to the carbon next to the desorbed C 2 H 4 group. The same hydrogen migration is thought to contribute to H 2 loss (Chen & Luo 2019) and CH + n (n=4-6) fragments (Chacko et al 2020) from PAHs. Further confirmation of ethylene formation is achieved through the IR calculations of the fragment (m/z=181) which are shown in Fig.…”

Section: Confirmation Of the Ethylene Formationmentioning

confidence: 94%

“…The excited PAHs subsequently dissipate their excess energy via several competing channels: ionization, infrared emission, isomerization, and fragmentation (Tielens 2013). PAH fragmentation is believed to play an important role in the catalytic formation of H 2 (Rauls & Hornekaer 2008;Thrower et al 2012), as a source of small hydrocarbons (Chacko et al 2020), and as a part of more complex top-down interstellar chemistry (Zhen et al 2014). It is also an indicator of whether or not PAHs can survive in harsh interstellar environments (Reitsma et al 2014;Gatchell et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Top-down formation of ethylene from fragmentation of superhydrogenated polycyclic aromatic hydrocarbons

Tang

Simonsen

Jaganathan

et al. 2022

A&A

View full text Add to dashboard Cite

Context.Fragmentation is an important decay mechanism for polycyclic aromatic hydrocarbons (PAHs) under harsh interstellar conditions and represents a possible formation pathway for small molecules such as H 2 , C 2 H 2 and C 2 H 4 . Aims. Our aim is to investigate the dissociation mechanism of superhydrogenated PAHs that undergo energetic processing and the formation pathway of small hydrocarbons. Methods. We obtain, experimentally, the mass distribution of protonated tetrahydropyrene (C 16 H + 15 , [py + 5H] + ) and protonated hexahydropyrene (C 16 H + 17 , [py+7H] + ) upon collision induced dissociation (CID). The IR spectra of their main fragments are recorded by infrared multiple-photon dissociation (IRMPD). Extended tight-binding (GFN2-xTB) based molecular dynamics simulations are performed in order to provide the missing structure information in experiment and identify fragmentation pathways. The pathways for fragmentation are further investigated at a hybrid-density functional theory (DFT) and dispersion corrected level. Results. A strong signal for loss of 28 mass units of [py + 7H] + is observed both in the CID experiment and the MD simulation, while [py + 5H] + shows negligible signal for the product corresponding to a mass loss of 28. The 28 mass loss from [py + 7H] + is assigned to the loss of ethylene (C 2 H 4 ) and a good fit between the calculated and experimental IR spectrum of the resulting fragment species is obtained. Further DFT calculations show favorable kinetic pathways for loss of C 2 H 4 from hydrogenated PAH configurations involving three consecutive CH 2 molecular entities. Conclusions. This joint experimental and theoretical investigation proposes a chemical pathway of ethylene formation from fragmentation of superhydrogenated PAHs. This pathway is sensitive to hydrogenated edges (e.g. the degree of hydrogenation and the hydrogenated positions). The inclusion of this pathway in astrochemical models may improve the estimated abundance of ethylene.

show abstract

“…and thus c-C 3 H 2 is mostly destroyed by converting it back to an even larger molecule, c-C 3 H 3 + (Millar et al 1997). The ubiquity of C 2 H and c-C 3 H 2 supports a top-down formation mechanism by release from hydrogenated amorphous carbon, rather than a bottom-up synthesis by gas-phase reaction (Fossé et al 2000;Fuente et al 2003;Teyssier et al 2004;Pety et al 2005;Guzmán et al 2015;Chacko et al 2020) even in dark and diffuse clouds. Recent experimental (Duley et al 2015) and theoretical (Awad & Viti 2022) studies also support this scenario.…”

Section: Other N-bearing Moleculesmentioning

confidence: 99%

Physical and Chemical Properties of Galactic Molecular Gas toward QSO J1851+0035

Narita,

Sakamoto,

Koda

et al. 2024

ApJ

View full text Add to dashboard Cite

Atacama Large Millimeter/submillimeter Array (ALMA) data toward QSO J1851+0035 (l = 33.°498, b = +0.°194) were used to study absorption lines by Galactic molecular gas. We detected 17 species (CO, 13CO, C18O, HCO+, H13CO+, HCO, H2CO, C2H, c-C3H, c-C3H2, CN, HCN, HNC, CS, SO, SiO, and C) and set upper limits to 18 species as reference values for chemical models. About 20 independent velocity components at 4.7–10.9 kpc from the Galactic center were identified. Their column density and excitation temperature estimated from the absorption study, as well as the CO intensity distributions obtained from the FUGIN survey, indicate that the components with τ ≲1 correspond to diffuse clouds or cloud outer edges. Simultaneous multiple-Gaussian fitting of CO J = 1–0 and J = 2–1 absorption lines shows that these are composed of narrow- and broad-line components. The kinetic temperature empirically expected from the high HCN/HNC isomer ratio (≳4) reaches ≳40 K and the corresponding thermal width accounts for the line widths of the narrow-line components. CN-bearing molecules and hydrocarbons have tight and linear correlations within the groups. The CO/HCO+ abundance ratio showed a dispersion as large as 3 orders of magnitude with a smaller ratio in a smaller N(HCO+) (or lower A V) range. Some of the velocity components are detected in single-dish CO emission and ALMA HCO+ absorption but without corresponding ALMA CO absorption. This may be explained by the mixture of clumpy CO emitters not resolved with the ∼1 pc single-dish beam surrounded by extended components with a very low CO/HCO+ abundance ratio (i.e., CO-poor gas).

show abstract

Polycyclic Aromatic Hydrocarbons as a Source for (N = 4–6) and C₃H₂ in the Interstellar Medium

Cited by 8 publications

References 85 publications

Polarizability in Astrochemical Studies of Complex Carbon-Based Compounds

Polarizability in Astrochemical Studies of Complex Carbon-Based Compounds

Top-down formation of ethylene from fragmentation of superhydrogenated polycyclic aromatic hydrocarbons

Physical and Chemical Properties of Galactic Molecular Gas toward QSO J1851+0035

Contact Info

Product

Resources

About

Polycyclic Aromatic Hydrocarbons as a Source for (N = 4–6) and C3H2 in the Interstellar Medium

Cited by 8 publications

References 85 publications

Polarizability in Astrochemical Studies of Complex Carbon-Based Compounds

Polarizability in Astrochemical Studies of Complex Carbon-Based Compounds

Top-down formation of ethylene from fragmentation of superhydrogenated polycyclic aromatic hydrocarbons

Physical and Chemical Properties of Galactic Molecular Gas toward QSO J1851+0035

Contact Info

Product

Resources

About

Polycyclic Aromatic Hydrocarbons as a Source for (N = 4–6) and C₃H₂ in the Interstellar Medium