Atomic hydrogen interactions with small polycyclic aromatic hydrocarbons cations

Schlathölter, Thomas; Mostafa, Yahia; Kamman, Amber; Dongelmans, Arnold; Arribard, Yann; Cazaux, S.; Hoekstra, Ronnie

doi:10.1140/epjd/e2020-10111-y

Cited by 5 publications

(6 citation statements)

References 33 publications

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“…Meanwhile, there are no clear mass peaks that can attribute to the PAH fragments (loss of C 2 H 2 ) in our obtained mass spectra. We suppose that the non-appearance of fragmentation mainly attributes to the superior stability of large PAH (e.g., HBC) upon hydrogenation compared to smaller PAH (e.g., pyrene, C 16 H 10; Schlathölter et al 2020). And due to that, the large PAHs may play an important role as an ideal catalyst for hydrogen formation in the ISM.…”

Section: Resultsmentioning

confidence: 99%

“…as typical examples to theoretically study deuteration or hydrogenation and hydrogen/deuterium exchange processes on cationic PAHs. Based on the molecular structural symmetry of HBC + , H/D attachment and abstraction tend to occur on the outer carbon sites according to previous experimental and theoretical investigations (Rauls & Hornekaer 2008;Elias et al 2009;Cazaux et al 2016;Schlathölter et al 2020). As a result, we label the available outer carbon sites as 1−5 in Figure 1 (2 and 5 as well as 3 and 4 are equal).…”

Section: Quantum Calculation Resultsmentioning

confidence: 99%

“…In other words, the attachment energy barriers are almost vanished, which we suppose may not play an important role in the hydrogenation process. So only the exothermic energy for the reaction pathways needs to be considered in the theoretical calculation (Cazaux et al 2016;Schlathölter et al 2020). For the ion-atom collision reactions under the gasphase conditions, we consider the reaction collision can happen if the exothermic energy is around or higher than ∼1.0 eV.…”

Section: Quantum Calculation Resultsmentioning

confidence: 99%

“…Draine (2006) showed that collisions of D with PAH cations and D + with PAHs could incorporate D into PAHs and efficiently deplete D from the gas phase in cool diffuse clouds. For the smaller PAHs, pyrene (C 16 H 10 ) cations' exposure to atomic D have been investigated, and clear lines of evidence for HD/D 2 abstraction reactions of Eley−Rideal type were found (Schlathölter et al 2020). In a combined experimental and theoretical study, coronene (C 24 H 12 ) hydrogenation is following a well-defined sequence of hydrogenation sites that has later been confirmed by means of infrared spectroscopy (Cazaux et al 2016(Cazaux et al , 2019.…”

Section: Introductionmentioning

confidence: 91%

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Gas-phase Hydrogen/Deuterium Exchange on Large, Astronomically Relevant Cationic PAHs

Zhang

Yang

et al. 2022

ApJ

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To examine the gas-phase hydrogen/deuterium exchange on large, astronomically relevant cationic polycyclic aromatic hydrocarbons (PAHs), the ion-molecule collision reaction between C42H18 + (hexa-peri-hexabenzocoronene cations, HBC+) and D atoms is studied. The experimental results show that the deuterated HBC cations ([C42H m D n ]+, m+2 ∗ n up to ∼54) are efficiently formed, and an effective hydrogen/deuterium exchange is determined. The structure of newly formed deuterated HBC cations and the bonding energy for these reaction pathways are investigated with quantum theoretical calculations. The exothermic energy for each reaction pathway is relatively high, and the existence of competition between deuteration and dedeuteration and of hydrogen/deuterium exchange is confirmed. A kinetic model is constructed to simulate the deuteration and hydrogenation processes and the hydrogen/deuterium exchange on HBC+ as a function of the reaction time over the experimental and typical astrophysical conditions. We infer that if we do not consider other chemical evolution processes (e.g., photoevolution), then cationic PAHs will reach the final equilibrium state (reaction with H/D atoms) very quickly regardless of the initial state of PAHs, and deuterated cationic PAHs are scarce in the interstellar medium.

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Section: Resultsmentioning

confidence: 99%

Section: Quantum Calculation Resultsmentioning

confidence: 99%

Section: Quantum Calculation Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

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Gas-phase Hydrogen/Deuterium Exchange on Large, Astronomically Relevant Cationic PAHs

Zhang

Yang

et al. 2022

ApJ

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“…While not definitively identified in space, laboratory (Wagner et al 2000;Sandford et al 2013) and computational (Pauzat & Ellinger 2001;Mackie et al 2018) studies have suggested that HPAHs may contribute to the so-called Aromatic Infrared Bands (Tielens 2008) at wavelengths between 3.4-3.6 µm. Highly hydrogenated PAHs have been shown to be readily formed under a variety of circumstances (Thrower et al 2012;Boschman et al 2012;Klaerke et al 2013;Thrower et al 2014;Cazaux et al 2016;Cruz-Diaz et al 2020;Schlathölter et al 2020), and efficient photo-induced H 2 formation from HPAHs has been demonstrated (Vala et al 2009;Szczepanski et al 2010;Fu et al 2011;Foley et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Competitive Dehydrogenation and Backbone Fragmentation of Superhydrogenated PAHs: A Laboratory Study

Stockett

Avaldi

Bolognesi

et al. 2021

ApJ

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Super-hydrogenated Polycyclic Aromatic Hydrocarbons (PAHs) have been suggested to catalyze the formation of H 2 in certain regions of space, but it remains unclear under which circumstances this mechanism is viable given the reduced stability of super-hydrogenated PAHs. We report a laboratory study on the stability of the smallest pericondensed PAH, pyrene (C 16 H 10+N , with N = 4, 6, and 16 additional H atoms), against photodestruction by single vacuum ultraviolet photons using the Photo-Electron Photo-Ion Coincidence technique. For N = 4, we observe a protective effect of hydrogenation against the loss of native hydrogens, in the form of an increase in the appearance energies of the C 16 H + 9 and C 16 H + 8 daughter ions compared to those reported for pristine pyrene (C 16 H 10 ). No such effect is seen for N = 6 or 16, where the weakening effect of replacing aromatic bonds with aliphatic ones outweighs the buffering effect of the additional hydrogen atoms. The onset of fragmentation occurs at similar internal energies for N = 4 and 6, but is significantly lower for N = 16. In all three cases, H-loss and C m H n -loss (m ≥ 1, carbon backbone fragmentation) channels open at approximately the same energy. The branching fractions of the primary channels favor H-loss for N = 4, C m H n -loss for N = 16, and are roughly equal for the intermediate N = 6. We conclude that super-hydrogenated pyrene is probably too small to support catalytic H 2 -formation, while trends in the current and previously reported data suggest that larger PAHs may serve as catalysts up to a certain level of hydrogenation.

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Aromatic hydrocarbons as Molecular Propellants for Electric Propulsion Thrusters

Borrfors,

Harding,

Weissenrieder

et al. 2023

J Electr Propuls

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The aromatic hydrocarbons (AHs) fluorobenzene, naphthalene, and 1-fluoronaphthalene are introduced as promising alternatives to xenon as propellant for in-space electric propulsion (EP). These storable molecules have similar mass, lower cost, and lower ionization energies compared to xenon, as well as the critical advantage of low post-ionization fragmentation compared to other molecular propellant candidates. The ionization characteristics of AHs are compared with those of xenon and the diamondoid adamantane, previously evaluated as a molecular propellant for EP. Quantum chemical calculations and BEB theory together with 25 eV electron ionization mass spectrometry (EI-MS) measurements have been used to predict the fragmentation of the AHs and adamantane when ionized in a plasma with an electron temperature of 7 eV (a typical electron temperature in EP plasmas). A high fraction (81 − 86%) of the detected AH ions originate from intact molecules, compared to 34% for adamantane, indicating extraordinarily low fragmentation for the selected AHs. The ionization potential of the AHs is similar to that of adamantane but lower compared to xenon (8.14–9.2 eV for the AHs, 9.25 for adamantane and 12.13 eV for xenon). BEB calculations have also been used to predict total ionization cross sections. The calculated ionization cross section of the AHs is comparable to that of adamantane but 3–5 times higher than that of xenon, which together with the low ionization potential can contribute to more efficient ionization. The AHs may have the potential to perform better than xenon, despite the absence of fragmentation in xenon.

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Atomic hydrogen interactions with small polycyclic aromatic hydrocarbons cations

Cited by 5 publications

References 33 publications

Gas-phase Hydrogen/Deuterium Exchange on Large, Astronomically Relevant Cationic PAHs

Gas-phase Hydrogen/Deuterium Exchange on Large, Astronomically Relevant Cationic PAHs

Competitive Dehydrogenation and Backbone Fragmentation of Superhydrogenated PAHs: A Laboratory Study

Aromatic hydrocarbons as Molecular Propellants for Electric Propulsion Thrusters

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