Similarities and dissimilarities in the fragmentation of polycyclic aromatic hydrocarbon cations: A case study involving three dibenzopyrene isomers

Hróðmarsson, Helgi Rafn; Bouwman, Jordy; Tielens, A. G. G. M.; Linnartz, H.

doi:10.1016/j.ijms.2022.116834

Cited by 14 publications

(18 citation statements)

References 65 publications

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“…This behavior, although difficult to model, provides a way to disentangle both isomers. Recently, Hrodmarsson et al used an MPD activation scheme at 620 nm to disentangle three isomers of dibenzopyrene (DBP, ). The authors measured the dissociation curves as a function of the number of pulses and reported similarities but also differences in the dissociation patterns between the species studied, concluding, however, that their interpretation was not straightforward.…”

Section: Discussionmentioning

confidence: 99%

Isomer Differentiation of Trapped C₁₆H₁₀⁺ Using Low-Energy Collisions and Visible/VUV Photons

et al. 2022

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Polycyclic aromatic hydrocarbons are major species in astrophysical environments, and this motivates their study in samples of astrochemical interest such as meteorites and laboratory analogues of stardust. Molecular analyses of carbonaceous matter in these samples show a dominant peak at m/z = 202.078 corresponding to C 16 H 10 . Obtaining information on the associated isomeric structures is a challenge for the molecular analysis of samples available in very small quantities (mg or less). Here we show that coupling laser desorption ionization mass spectrometry with ion trapping opens up the possibility of unraveling isomers by activating ion fragmentation via collisions or photon absorption. We report the best criteria for differentiating isomers with comparable dissociation energies, namely pyrene, fluoranthene, and 9-ethynylphenanthrene, on the basis of the parent dissociation curve and the ratio of dehydrogenation channels. Photoabsorption schemes (multiple photon absorption in the visible range and single photon absorption at 10.5 eV) are more effective in differentiating these isomers than activation by low energy collisions. The impact of the activation scheme on the fragmentation kinetics and dehydrogenation pathways is discussed. By analyzing the 10.5 eV photodissociation measurements with a simple kinetic model, we were able to derive a branching ratio for the H and 2H/H 2 loss channels of the parent ions. The results suggest a role in the formation of H 2 for bay hydrogens that are present in both fluoranthene and 9-ethynylphenanthrene. In addition, we suggest for the latter the presence of a highly competitive 2H loss channel, possibly associated with the formation of a pentagonal ring.

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Section: Discussionmentioning

confidence: 99%

Isomer Differentiation of Trapped C₁₆H₁₀⁺ Using Low-Energy Collisions and Visible/VUV Photons

et al. 2022

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“…Previous investigations show that polycyclic aromatic hydrocarbon (PAH) cations contained in ion traps exposed to intense bursts of laser light eventually decompose to form bare carbon cluster cations (C n + ) through loss of H, H 2 , and small hydrocarbon molecules. − Similar photofragmentation processes are postulated to occur in interstellar space driven by the flux of harsh UV radiation. The C 2 n +1 H + species examined in the current work can be viewed as the penultimate species in this dehydrogenation process.…”

Section: Astrophysical Considerationsmentioning

confidence: 97%

Disentangling Electronic Spectra of Linear and Cyclic Hydrogenated Carbon Cluster Cations, C_2n+1H⁺ (n = 3–10)

et al. 2022

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Electronic spectra are measured for protonated carbon clusters (C2n+1H+) containing between 7 and 21 carbon atoms. Linear and cyclic C2n+1H+ isomers are separated and selected using a drift tube ion mobility stage before being mass selected and introduced into a cryogenically cooled ion trap. Spectra are measured using a two-color resonance-enhanced photodissociation strategy, monitoring C2n+1 + photofragments (H atom loss channel) as a function of excitation wavelength. The linear C7H+, C9H+, C11H+, C13H+, C15H+, and C17H+ clusters, which are predicted to have polyynic structures, possess sharp 11Σ+ ← X̃1Σ+ transitions with well-resolved vibronic progressions in C–C stretch vibrational modes. The vibronic features are reproduced by spectral simulations based on vibrational frequencies and geometries calculated with time-dependent density functional theory (ωB97X-D/cc-pVDZ level). The cyclic C15H+, C17H+, C19H+, and C21H+ clusters exhibit weak, broad transitions at a shorter wavelength compared to their linear counterparts. Wavelengths for the origin transitions of both linear and cyclic isomers shift linearly with the number of constituent carbon atoms, indicating that in both cases, the clusters possess a common structural motif.

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“…However, the impact ionization studies of organic projectiles have been limited to polystyrene and aliphatic poly(methyl methacrylate) latex. − The latter polymer is solely aliphatic, while the former polymer contains both aliphatic and aromatic bonds, so neither is a satisfactory synthetic mimic for PAH dust grains. The wholly aromatic character of PAHs should mean that higher impact energies are required to break chemical bonds and distinctive molecular fragments are anticipated in their mass spectra. − This paper describes the first study of the impact ionization behavior of a suitable synthetic mimic for PAH-based dust grains. Alternative analytical methods such as electrospray, chemical ionization, and electron impact ionization (followed by laser dissociation) do not provide comparable data to those obtained in dust impact ionization (DII) experiments because the chemical composition of the resulting ionic plasma is strongly dependent on the impact velocity.…”

Section: Introductionmentioning

confidence: 99%

Impact Ionization Mass Spectra of Polypyrrole-Coated Anthracene Microparticles: A Useful Mimic for Cosmic Polycyclic Aromatic Hydrocarbon Dust

Mikula,

Sternovsky,

Armes

et al. 2024

ACS Earth Space Chem.

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Polycyclic aromatic hydrocarbons (PAHs) are abundantly present in the interstellar medium and in our solar system and lock up a significant fraction of cosmic carbon. They are found to be present in interstellar and interplanetary dust particles. Impact ionization mass spectrometers on future space missions can detect such dust particles and assess their composition; it is essential to understand the impact ionization behavior of PAH-based dust particles impinging on metal targets at relevant velocities. To date, impact ionization studies of fast-moving organic-rich dust particles have been limited to vinyl polymers, such as polystyrene or poly(methyl methacrylate). Recently, PAH anthracene has been prepared in the form of microparticles suitable for use in dust accelerators. Here, we present the first comprehensive study of the impact ionization mass spectra of such anthracene microparticles impinging on a gold target at 2–35 km s–1. The mass spectra recorded for the resulting ionic plasma are strongly dependent on the incident velocity with impacts at 6–10 km s–1 being optimal for generating distinctive spectral features that enable the identification of the parent molecule. Under these conditions, the protonated parent ion and doubly protonated radical, C14H11 +, and C14H12 •+ (as well as other diagnostic cluster species such as (C14H10)(CH)+ and (C14H11)(C2H)+) can be reproducibly identified. We find that the impact ionization spectra always differ markedly from the electron impact ionization mass spectra reported for anthracene in the literature regardless of the impact velocity. This study highlights the importance of performing fundamental impact ionization studies of organic particles by using a dust accelerator to enable the interpretation of data collected in future space missions.

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Similarities and dissimilarities in the fragmentation of polycyclic aromatic hydrocarbon cations: A case study involving three dibenzopyrene isomers

Cited by 14 publications

References 65 publications

Isomer Differentiation of Trapped C₁₆H₁₀⁺ Using Low-Energy Collisions and Visible/VUV Photons

Isomer Differentiation of Trapped C₁₆H₁₀⁺ Using Low-Energy Collisions and Visible/VUV Photons

Disentangling Electronic Spectra of Linear and Cyclic Hydrogenated Carbon Cluster Cations, C_2n+1H⁺ (n = 3–10)

Impact Ionization Mass Spectra of Polypyrrole-Coated Anthracene Microparticles: A Useful Mimic for Cosmic Polycyclic Aromatic Hydrocarbon Dust

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Similarities and dissimilarities in the fragmentation of polycyclic aromatic hydrocarbon cations: A case study involving three dibenzopyrene isomers

Cited by 14 publications

References 65 publications

Isomer Differentiation of Trapped C16H10+ Using Low-Energy Collisions and Visible/VUV Photons

Isomer Differentiation of Trapped C16H10+ Using Low-Energy Collisions and Visible/VUV Photons

Disentangling Electronic Spectra of Linear and Cyclic Hydrogenated Carbon Cluster Cations, C2n+1H+ (n = 3–10)

Impact Ionization Mass Spectra of Polypyrrole-Coated Anthracene Microparticles: A Useful Mimic for Cosmic Polycyclic Aromatic Hydrocarbon Dust

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Isomer Differentiation of Trapped C₁₆H₁₀⁺ Using Low-Energy Collisions and Visible/VUV Photons

Isomer Differentiation of Trapped C₁₆H₁₀⁺ Using Low-Energy Collisions and Visible/VUV Photons

Disentangling Electronic Spectra of Linear and Cyclic Hydrogenated Carbon Cluster Cations, C_2n+1H⁺ (n = 3–10)