1
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Sundararajan P, Candian A, Kamer J, Linnartz H, Tielens AGGM. Photofragmentation of corannulene (C 20H 10) and sumanene (C 21H 12) cations in the gas phase and their astrophysical implications. Phys Chem Chem Phys 2024; 26:19332-19348. [PMID: 38966905 DOI: 10.1039/d4cp01247j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/06/2024]
Abstract
Aromatic infrared bands (AIBs) dominate the mid-infrared spectra of many galactic and extragalactic sources. These AIBs are generally attributed to fluorescence emission from aromatic molecules. Unified efforts from experimentalists and theoreticians to assign these AIB features have recently received additional impetus with the launch of the James Webb Space Telescope (JWST) as the Mid-InfraRed Instrument (MIRI) delivers a mid-IR spectrum with greatly increased sensitivity and spectral resolution. PAHs in space can exist in either neutral or ionic form, absorb UV photons and undergo fragmentation, becoming a rich source of small hydrocarbons. This top-down mechanism of larger PAHs fragmenting into smaller species is of utmost importance in photo-dissociation regions (PDR) in space. In this work, we experimentally and theoretically investigate the photo-fragmentation pathways of two astronomically significant PAH cations - corannulene (C20H10) and sumanene (C21H12), which are structural motifs of fullerene C60, to understand their sequential fragmentation pathways. The photo-fragmentation experiments exhibit channels that are significantly different from planar PAHs. The breakdown of the carbon skeleton is found to follow different pathways for C20H10 and C21H12 because of the number and positioning of pentagon rings, yet the most abundant low mass cations produced by these two species are found to be similar. The low mass cations showcased in this work could be of interest due to their possible astronomical detections. For completeness, the qualitative photofragmentation behaviour of dicationic corannulene and sumanene has also been investigated, but the potential energy surface of these dications is beyond the scope of this paper.
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Affiliation(s)
- Pavithraa Sundararajan
- Laboratory for Astrophysics, Leiden University, PO Box 9513, NL-2300, RA Leiden, The Netherlands.
- Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
| | - Alessandra Candian
- Anton Pannekoek Institute, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
| | - Jerry Kamer
- Laboratory for Astrophysics, Leiden University, PO Box 9513, NL-2300, RA Leiden, The Netherlands.
- Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
| | - Harold Linnartz
- Laboratory for Astrophysics, Leiden University, PO Box 9513, NL-2300, RA Leiden, The Netherlands.
- Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
| | - Alexander G G M Tielens
- Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
- Astronomy Department, University of Maryland, College Park, MD 20742, USA
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2
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Panchagnula S, Kamer J, Candian A, Hrodmarsson HR, Linnartz H, Bouwman J, Tielens AGGM. Laser-induced fragmentation of coronene cations. Phys Chem Chem Phys 2024; 26:18557-18570. [PMID: 38884178 DOI: 10.1039/d4cp01301h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
Polycyclic aromatic hydrocarbons are an important component of the interstellar medium of galaxies and photochemistry plays a key role in the evolution of these species in space. Here, we explore the photofragmentation behaviour of the coronene cation (C24H12˙+) using time-of-flight mass spectrometry. The experiments show photodissociation fragmentation channels including the formation of bare carbon clusters (Cn˙+) and hydrocarbon chains (CnHx+). The mass spectrum of coronene is dominated by peaks from C11˙+ and C7H+. Density functional theory was used to calculate relative energies, potential dissociation pathways, and possible structures for relevant species. We identify 6-6 → 5-7 ring isomerisation as a key step in the formation of both the bare carbon clusters and the hydrocarbon chains observed in this study. We present the dissociation mechanism outlined here as a potential formation route for C60 and other astrochemically relevant species.
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Affiliation(s)
- Sanjana Panchagnula
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, 2300 RA, Leiden, The Netherlands.
- Leiden Observatory, Leiden University, 2300 RA, Leiden, The Netherlands
| | - Jerry Kamer
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, 2300 RA, Leiden, The Netherlands.
| | - Alessandra Candian
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Helgi R Hrodmarsson
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, 2300 RA, Leiden, The Netherlands.
| | - Harold Linnartz
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, 2300 RA, Leiden, The Netherlands.
| | - Jordy Bouwman
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, 2300 RA, Leiden, The Netherlands.
| | - Alexander G G M Tielens
- Leiden Observatory, Leiden University, 2300 RA, Leiden, The Netherlands
- Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA
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3
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Tikhonov DS, Lee JWL, Schnell M. On the thermodynamic stability of polycations. J Chem Phys 2024; 160:244110. [PMID: 38934634 DOI: 10.1063/5.0207526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
We present a simple approximation to estimate the largest charge that a given molecule can hold until fragmentation into smaller charged species becomes more energetically favorable. This approximation solely relies on the ionization potentials, electron affinities of the parent and fragment species, and also on the neutral parent's dissociation energy. By parameterizing these quantities, it is possible to obtain analytical phase diagrams of polycationic stability. We demonstrate the applicability of this approach by discussing the maximal charge dependence on the size of the molecular system. A numerical demonstration for linear polyenes, monocyclic annulenes, and helium clusters is provided.
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Affiliation(s)
- Denis S Tikhonov
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Jason W L Lee
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Melanie Schnell
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
- Institute of Physical Chemistry, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 1, 24118 Kiel, Germany
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4
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Schleier D, Kamer J, Jiao A, Schneider GF, Linnartz H, Bouwman J. Photoprocessing of cationic triazacoronene: dissociation characteristics of polycyclic aromatic nitrogen heterocycles in interstellar environments. Phys Chem Chem Phys 2024; 26:15547-15558. [PMID: 38756091 DOI: 10.1039/d4cp01387e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
Polycyclic aromatic nitrogen heterocycles (PANHs) are present in various astronomical environments where they are subjected to intense radiation. Their photodissociation pathways give crucial insights into the cycle of matter in the universe, yet so far only the dissociation characteristics of few PANHs have been investigated. Moreover, most experiments use single photon techniques that only reveal the initial dissociation step, and are thus unsuited to replicate astronomical environments and timescales. In this work, we use the Instrument for the Photodynamics of PAHs (i-PoP) at the Laboratory for Astrophysics to simulate the interstellar photodissociation of a model PANH, cationic triazacoronene (TAC˙+, C21H9N3). Comparing the observed fragments to similar PAHs such as the isoelectronic coronene can give mechanistic insight into PAH dissociation. For coronene the major photodissociation products were found to be C9H+, C10+, and C11+. In contrast, fragmentation in TAC˙+ is initiated by up to three HCN losses often in combination with H- or H2 losses. In the lower mass region, the fragments show similarities to comparable PAHs like coronene, but for TAC˙+ the inclusion of nitrogen atoms into the ionic fragments in the form of e.g. (di)cyanopolyynes is also observed. These nitrogen-containing species may be important tracers of regions in interstellar space where interstellar PANHs are being photodissociated.
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Affiliation(s)
- Domenik Schleier
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
- Lehrstuhl Technische Thermodynamik, Fakultät für Maschinenbau, Universität Paderborn, Warburger Str. 100, 33098 Paderborn, Germany.
| | - Jerry Kamer
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
| | - Andy Jiao
- Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
| | - Grégory F Schneider
- Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
| | - Harold Linnartz
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
| | - Jordy Bouwman
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA.
- Department of Chemistry, University of Colorado, Boulder, CO 80309, USA
- Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT), NASA/SSERVI, Boulder, CO 80309, USA
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5
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van der Burgt PJM, Gradziel ML. Coincidence mass spectrometry study of double ionization of pyrene by 70 eV electron impact. Phys Chem Chem Phys 2024; 26:10688-10697. [PMID: 38511630 DOI: 10.1039/d4cp00443d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
We have performed coincidence mass spectrometry of fragmentation of pyrene molecules by 70 eV electron impact. Ionized fragments have been mass selected using a reflectron time-of-flight mass spectrometer, and a field programmable gate array has been used for the timing of the electron and ion extraction pulses and for the event-by-event detection of the ions. Double ionization results in a number of prominent fragmentations producing two singly-ionized fragments with kinetic energies of up to a few eV. A number of fragmentations produce ions with four or more carbon atoms, which can only be formed by the breaking of at least three C-C bonds.
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Affiliation(s)
- Peter J M van der Burgt
- Department of Experimental Physics, National University of Ireland Maynooth, Maynooth, Co, Kildare, Ireland.
| | - Marcin L Gradziel
- Department of Experimental Physics, National University of Ireland Maynooth, Maynooth, Co, Kildare, Ireland.
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6
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Chan DH, Wills JL, Tandy JD, Burchell MJ, Wozniakiewicz PJ, Alesbrook LS, Armes SP. Synthesis of Autofluorescent Phenanthrene Microparticles via Emulsification: A Useful Synthetic Mimic for Polycyclic Aromatic Hydrocarbon-Based Cosmic Dust. ACS APPLIED MATERIALS & INTERFACES 2023; 15:54039-54049. [PMID: 37944021 PMCID: PMC10685351 DOI: 10.1021/acsami.3c08585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 10/19/2023] [Accepted: 10/24/2023] [Indexed: 11/12/2023]
Abstract
Phenanthrene is the simplest example of a polycyclic aromatic hydrocarbon (PAH). Herein, we exploit its relatively low melting point (101 °C) to prepare microparticles from molten phenanthrene droplets by conducting high-shear homogenization in a 3:1 water/ethylene glycol mixture at 105 °C using poly(N-vinylpyrrolidone) as a non-ionic polymeric emulsifier. Scanning electron microscopy studies confirm that this protocol produces polydisperse phenanthrene microparticles with a spherical morphology: laser diffraction studies indicate a volume-average diameter of 25 ± 21 μm. Such projectiles are fired into an aluminum foil target at 1.87 km s-1 using a two-stage light gas gun. Interestingly, the autofluorescence exhibited by phenanthrene aids analysis of the resulting impact craters. More specifically, it enables assessment of the spatial distribution of any surviving phenanthrene in the vicinity of each crater. Furthermore, these phenanthrene microparticles can be coated with an ultrathin overlayer of polypyrrole, which reduces their autofluorescence. In principle, such core-shell microparticles should be useful for assessing the extent of thermal ablation that is likely to occur when they are fired into aerogel targets. Accordingly, polypyrrole-coated microparticles were fired into an aerogel target at 2.07 km s-1. Intact microparticles were identified at the end of carrot tracks and their relatively weak autofluorescence suggests that thermal ablation during aerogel capture did not completely remove the polypyrrole overlayer. Thus, these new core-shell microparticles appear to be useful model projectiles for assessing the extent of thermal processing that can occur in such experiments, which have implications for the capture of intact PAH-based dust grains originating from cometary tails or from plumes emanating from icy satellites (e.g., Enceladus) in future space missions.
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Affiliation(s)
- Derek
H. H. Chan
- Dainton
Building, Department of Chemistry, University
of Sheffield, Brook Hill, Sheffield, South
Yorkshire S3 7HF, U.K.
| | - Jessica L. Wills
- School
of Physics and Astronomy, University of
Kent, Canterbury, Kent CT2 7NH, U.K.
| | - Jon D. Tandy
- School
of Chemistry and Forensic Science, University
of Kent, Canterbury, Kent CT2 7NZ, U.K.
| | - Mark J. Burchell
- School
of Physics and Astronomy, University of
Kent, Canterbury, Kent CT2 7NH, U.K.
| | | | - Luke S. Alesbrook
- School
of Physics and Astronomy, University of
Kent, Canterbury, Kent CT2 7NH, U.K.
| | - Steven P. Armes
- Dainton
Building, Department of Chemistry, University
of Sheffield, Brook Hill, Sheffield, South
Yorkshire S3 7HF, U.K.
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7
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Garcia GA, Dontot L, Rapacioli M, Spiegelman F, Bréchignac P, Nahon L, Joblin C. Electronic effects in the dissociative ionisation of pyrene clusters. Phys Chem Chem Phys 2023; 25:4501-4510. [PMID: 36722859 DOI: 10.1039/d2cp05679h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We present a combined experimental and theoretical study on the dissociative ionisation of clusters of pyrene. We measured the experimental appearance energies in the photon energy range 7.2-12.0 eV of the fragments formed from neutral monomer loss for clusters up to the hexamer. The results obtained show a deviation from statistical dissociation. From electronic structure calculations, we suggest that the role of excited states must be considered in the interpretation of experimental results, even in these relatively large systems. Non-statistical effects in the dissociative ionization process of polycyclic aromatic hydrocarbon (PAH) clusters may have an impact on the assessment of mechanisms determining the stability of these clusters in astrophysical environments.
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Affiliation(s)
- Gustavo A Garcia
- Synchrotron SOLEIL, L'Orme des Merisiers, Départamentale 128, 91190 Saint Aubin, France.
| | - Léo Dontot
- Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse III - Paul Sabatier, CNRS, CNES, 9 avenue du Colonel Roche, BP 44346, F-31028 Toulouse, France.,Laboratoire de Chimie et Physique Quantiques, FERMI, Université de Toulouse III - Paul Sabatier, CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - Mathias Rapacioli
- Laboratoire de Chimie et Physique Quantiques, FERMI, Université de Toulouse III - Paul Sabatier, CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - Fernand Spiegelman
- Laboratoire de Chimie et Physique Quantiques, FERMI, Université de Toulouse III - Paul Sabatier, CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - Philippe Bréchignac
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Saclay, F-91405 Orsay, France
| | - Laurent Nahon
- Synchrotron SOLEIL, L'Orme des Merisiers, Départamentale 128, 91190 Saint Aubin, France.
| | - Christine Joblin
- Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse III - Paul Sabatier, CNRS, CNES, 9 avenue du Colonel Roche, BP 44346, F-31028 Toulouse, France
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8
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Banhatti S, Rap DB, Simon A, Leboucher H, Wenzel G, Joblin C, Redlich B, Schlemmer S, Brünken S. Formation of the acenaphthylene cation as a common C 2H 2-loss fragment in dissociative ionization of the PAH isomers anthracene and phenanthrene. Phys Chem Chem Phys 2022; 24:27343-27354. [PMID: 36326610 PMCID: PMC9673687 DOI: 10.1039/d2cp03835h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 10/21/2022] [Indexed: 09/19/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are thought to be a major constituent of astrophysical environments, being the carriers of the ubiquitous aromatic infrared bands (AIBs) observed in the spectra of galactic and extra-galactic sources that are irradiated by ultraviolet (UV) photons. Small (2-cycles) PAHs were unambiguously detected in the TMC-1 dark cloud, showing that PAH growth pathways exist even at low temperatures. The processing of PAHs by UV photons also leads to their fragmentation, which has been recognized in recent years as an alternative route to the generally accepted bottom-up chemical pathways for the formation of complex hydrocarbons in UV-rich interstellar regions. Here we consider the C12H8+ ion that is formed in our experiments from the dissociative ionization of the anthracene and phenanthrene (C14H10) molecules. By employing the sensitive action spectroscopic scheme of infrared pre-dissociation (IRPD) in a cryogenic ion trap instrument coupled to the free-electron lasers at the FELIX Laboratory, we have recorded the broadband and narrow line-width gas-phase IR spectra of the fragment ions (C12H8+) and also the reference spectra of three low energy isomers of C12H8+. By comparing the experimental spectra to those obtained from quantum chemical calculations we have identified the dominant structure of the fragment ion formed in the dissociation process to be the acenaphthylene cation for both isomeric precursors. Ab initio molecular dynamics simulations are presented to elucidate the fragmentation process. This result reinforces the dominant role of species containing a pentagonal ring in the photochemistry of small PAHs.
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Affiliation(s)
- Shreyak Banhatti
- I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany.
| | - Daniël B Rap
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED, Nijmegen, The Netherlands.
| | - Aude Simon
- Laboratoire de Chimie et Physique Quantiques (LCPQ), Fédération FeRMI, CNRS & Université Toulouse III - Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
| | - Heloïse Leboucher
- Laboratoire de Chimie et Physique Quantiques (LCPQ), Fédération FeRMI, CNRS & Université Toulouse III - Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
| | - Gabi Wenzel
- Center for Interstellar Catalysis (InterCat), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Christine Joblin
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
| | - Britta Redlich
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED, Nijmegen, The Netherlands.
| | - Stephan Schlemmer
- I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany.
| | - Sandra Brünken
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED, Nijmegen, The Netherlands.
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9
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Vinitha MV, Mundlapati VR, Marciniak A, Carlos M, Sabbah H, Bonnamy A, Noguès L, Murat D, Coeur-Joly O, Joblin C. Isomer Differentiation of Trapped C 16H 10+ Using Low-Energy Collisions and Visible/VUV Photons. J Phys Chem A 2022; 126:5632-5646. [PMID: 35951364 DOI: 10.1021/acs.jpca.2c03304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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 C16H10. 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/H2 loss channels of the parent ions. The results suggest a role in the formation of H2 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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Affiliation(s)
- M Viswanathan Vinitha
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Venkateswara Rao Mundlapati
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Alexandre Marciniak
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Mickaël Carlos
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Hassan Sabbah
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Anthony Bonnamy
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Loïc Noguès
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - David Murat
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Odile Coeur-Joly
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - Christine Joblin
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
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10
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Zinck N, Bodi A, Mayer PM. VUV photoprocessing of oxygen-containing polycyclic aromatic hydrocarbons: iPEPICO study of the unimolecular dissociation of ionized benzofuran. CAN J CHEM 2022. [DOI: 10.1139/cjc-2022-0062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) are potential contributors to the 11.3 m band in interstellar observations. To further explore their role in the interstellar medium, we have investigated their fate after photoprocessing by VUV radiation; in particular, we studied the dissociative photoionization of the simplest OPAH, benzofuran, with imaging photoelectron photoion coincidence spectroscopy, iPEPICO. Ionized benzofuran dissociates by loss of CO, followed by a sequential H atom loss. The parallel HCO-loss channel, leading to the same bicyclic C7H5+ fragment ion, is not competitive at low excess energies above the ionization threshold. However, the collision-induced dissociation tandem mass spectrometry results suggest that CO and HCO may be formed in parallel at higher energies. An RRKM fragmentation model reproduced the iPEPICO data well assuming the initial 1,2-H shift transition state to be rate determining to CO loss. The breakdown diagram and the measured dissociation rates agreed well at the CBS-QB3-calculated activation energy of 2.99 eV, which could be relaxed to 3.25 eV, and only a slight adjustment of the ab initio activation entropy. The model barrier to sequential H-loss is larger than the computed H-loss threshold and the breakdown diagram rises less steeply than predicted, which indicates suprastatistical kinetic energy release after the tight H-transfer transition state of the first step. HCO cleavage is possible after a ring-opening transition state, which is looser than and isoenergetic with the CO-loss transition state. However, a subsequent ring formation transition state at 3.85 eV is moderately tight, which suppresses HCO loss at low excess energies.
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Affiliation(s)
- Nicholas Zinck
- University of Ottawa, 6363, Chemistry and Biomolecular Sciences, Ottawa, Ontario, Canada
| | - Andras Bodi
- Paul Scherrer Institut PSI, 28498, Laboratory for Synchrotron Radiation and Femtochemistry, Villigen, Aargau, Switzerland
| | - Paul M Mayer
- University of Ottawa, 6363, Chemistry and Biomolecular Sciences, Ottawa, Ontario, Canada,
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11
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Webster IJ, Beckham JL, Johnson ND, Duncan MA. Photochemical Synthesis and Spectroscopy of Covalent PAH Dimers. J Phys Chem A 2022; 126:1144-1157. [PMID: 35152698 DOI: 10.1021/acs.jpca.1c10606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Laser photochemistry of pressed-pellet samples of polycyclic aromatic hydrocarbons (PAHs) produces covalently bonded dimers and some higher polymers. This chemistry was discovered initially via laser desorption time-of-flight mass spectrometry experiments, which produced masses (m/z) of 2M-2 and 2M-4 (where M is the monomer parent mass). Dimers are believed to be formed from photochemical dehydrogenation and radical polymerization chemistry in the desorption plume. Replication of these ablation conditions at higher throughput allowed PAH dimers of pyrene, perylene, and coronene to be produced and collected in milligram quantities. Differential sublimation provided purification of the dimers and elimination of residual monomers. The purified dimers were investigated with UV-visible, IR, and Raman spectroscopy, complemented by computational studies using density functional theory at the CAM-B3LYP/def2-TZV level. Calculations and predicted spectra were calibrated by comparison with the corresponding monomers and used to determine the lowest energy dimer structures. Infrared and Raman spectroscopy provided few distinctive signatures, but UV-visible spectra detected new transitions for each dimer. The comparison of simulated and experimental spectra allows determination of the most prevalent structures for the PAH dimers. The work presented here provides interesting insights into the spectroscopy of extended aromatic systems and a new strategy for the photochemical synthesis of large PAH dimers.
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Affiliation(s)
- Ian J Webster
- Department of Chemistry, University of Georgia, Athens 30602-2556, Georgia
| | - Jacob L Beckham
- Department of Chemistry, University of Georgia, Athens 30602-2556, Georgia
| | - Natalie D Johnson
- Department of Chemistry, University of Georgia, Athens 30602-2556, Georgia
| | - Michael A Duncan
- Department of Chemistry, University of Georgia, Athens 30602-2556, Georgia
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12
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Schubert K, Schwob L, Dörner S, Girod M, MacAleese L, Pieterse CL, Schlathölter T, Techert S, Bari S. Ionization and Photofragmentation of Isolated Metalloporphyrin Cations Investigated by VUV Action Spectroscopy*. Chemistry 2021; 27:12371-12379. [PMID: 34137472 PMCID: PMC8457234 DOI: 10.1002/chem.202101515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Indexed: 11/13/2022]
Abstract
We investigated the photoionization and fragmentation of isolated metal protoporphyrin IX cations (MPPIX+ with M=Fe, Co, Zn) by means of vacuum-ultraviolet (VUV) action spectroscopy in the energy range of 8.5-35 eV. Experiments were carried out in the gas phase by interfacing an electrospray ionization tandem mass spectrometer with a synchrotron beamline. The mass spectra and partial ion yields show that photoexcitation of the precursor ions predominantly leads to . CH2 COOH radical side-chain losses of the macrocycle with additional methyl radical (. CH3 ) side-chain losses. Ionization, in contrast, leads to the formation of the intact ionized precursor and various doubly charged fragments which are mostly due to side-chain cleavages. Although statistical fragmentation dominates, we found evidence for non-statistical processes such as new fragments involving for example single and double H2 O losses, indicating that different relaxation mechanisms are at play upon photoionization compared to photoexcitation. The measured ionization energies were 9.6±0.2 eV, 9.4±0.2 eV and 9.6±0.2 eV for FePPIX+ , CoPPIX+ and ZnPPIX+ , respectively.
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Affiliation(s)
- Kaja Schubert
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
| | - Lucas Schwob
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
| | - Simon Dörner
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
| | - Marion Girod
- Univ LyonUniversité Claude Bernard Lyon 1CNRS UMR 5280Institut des Sciences Analytiques5 rue de la Doua69100VilleurbanneFrance
| | - Luke MacAleese
- Univ LyonUniversité Claude Bernard Lyon 1CNRS UMR 5306Institut Lumière Matière69622LyonFrance
| | | | - Thomas Schlathölter
- Zernike Institute for Advanced MaterialsUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
| | - Simone Techert
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
- Institut für RöntgenphysikGeorg-August-Universität GöttingenFriedrich-Hund-Platz 137077GöttingenGermany
| | - Sadia Bari
- Deutsches Elektronen-Synchrotron DESYNotkestr. 8522607HamburgGermany
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Peeters E, Mackie C, Candian A, Tielens AGGM. A Spectroscopic View on Cosmic PAH Emission. Acc Chem Res 2021; 54:1921-1933. [PMID: 33780617 DOI: 10.1021/acs.accounts.0c00747] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
ConspectusPolycyclic aromatic hydrocarbon molecules (PAHs) are ubiquitously present at high abundances in the Universe. They are detected through their infrared (IR) fluorescence UV pumped by nearby massive stars. Hence, their infrared emission is used to determine the star formation rate in galaxies, one of the key indicators for understanding the evolution of galaxies. Together with fullerenes, PAHs are the largest molecules found in space. They significantly partake in a variety of physical and chemical processes in space, influencing star and planet formation as well as galaxy evolution.Since the IR features from PAHs originate from chemical bonds involving only nearest neighbor atoms, they have only a weak dependence on the size and structure of the molecule, and it is therefore not possible to identify the individual PAH molecules that make up the cosmic PAH family. This strongly hampers the interpretation of their astronomical fingerprints. Despite the lack of identification, constraints can be set on the characteristics of the cosmic PAH family thanks to a joint effort of astronomers, physicists, and chemists.This Account presents the spectroscopic properties of the cosmic PAH emission as well as the intrinsic spectroscopic properties of PAHs and astronomical modeling of the PAH evolution required for the interpretation of the cosmic PAH characteristics. We discuss the observed spectral signatures tracing PAH properties such as charge, size, and structure and highlight the related challenges. We discuss the recent success of anharmonic calculations of PAH infrared absorption and emission spectra and outline the path forward. Finally, we illustrate the importance of models on PAH processing for the interpretation of the astronomical data in terms of the charge balance and PAH destruction.Throughout this Account, we emphasize that huge progress is on the horizon on the astronomical front. Indeed, the world is eagerly awaiting the launch of the James Webb Space Telescope (JWST). With its incredible improvement in spatial resolution, combined with its complete spectral coverage of the PAH infrared emission bands at medium spectral resolution and superb sensitivity, the JWST will revolutionize PAH research. Previous observations could only present spectra averaged over regions with vastly different properties, thus greatly confusing their interpretation. The amazing spatial resolution of JWST will disentangle these different regions. This will allow us to quantify precisely how PAHs are modified by the physical conditions of their host environment and thus trace how PAHs evolve across space. However, this will only be achieved when the necessary (and still missing) fundamental properties of PAHs, outlined in this Account, are known. We strongly encourage you to join this effort.
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Affiliation(s)
- Els Peeters
- Department of Physics & Astronomy, University of Western Ontario, London, Ontario, Canada
- Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada
- SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, California 94043, United States
| | - Cameron Mackie
- Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States
| | - Alessandra Candian
- van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Amsterdam, The Netherlands
- Leiden Observatory, Leiden University, Leiden, The Netherlands
| | - Alexander G. G. M. Tielens
- Leiden Observatory, Leiden University, Leiden, The Netherlands
- University of Maryland, College Park, Maryland 20742, United States
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Panchagnula S, Bouwman J, Rap DB, Castellanos P, Candian A, Mackie C, Banhatti S, Brünken S, Linnartz H, Tielens AGGM. Structural investigation of doubly-dehydrogenated pyrene cations. Phys Chem Chem Phys 2020; 22:21651-21663. [PMID: 32729589 DOI: 10.1039/d0cp02272a] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The vibrationally resolved spectra of the pyrene cation and doubly-dehydrogenated pyrene cation (C16H10˙+; Py+ and C16H8˙+; ddPy+) are presented. Infrared predissociation spectroscopy is employed to measure the vibrational spectrum of both species using a cryogenically cooled 22-pole ion trap. The spectrum of Py+ allows a detailed comparison with harmonic and anharmonic density functional theory (DFT) calculated normal mode frequencies. The spectrum of ddPy+ is dominated by absorption features from two isomers (4,5-ddPy+ and 1,2-ddPy+) with, at most, minor contributions from other isomers. These findings can be extended to explore the release of hydrogen from interstellar PAH species. Our results suggest that this process favours the loss of adjacent hydrogen atoms.
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Affiliation(s)
- Sanjana Panchagnula
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands.
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15
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Wenzel G, Joblin C, Giuliani A, Rodriguez Castillo S, Mulas G, Ji M, Sabbah H, Quiroga S, Peña D, Nahon L. Astrochemical relevance of VUV ionization of large PAH cations . ASTRONOMY AND ASTROPHYSICS 2020; 641:A98. [PMID: 33154599 PMCID: PMC7116310 DOI: 10.1051/0004-6361/202038139] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
CONTEXT As a part of interstellar dust, polycyclic aromatic hydrocarbons (PAHs) are processed by the interaction with vacuum ultra-violet (VUV) photons that are emitted by hot young stars. This interaction leads to the emission of the well-known aromatic infrared bands but also of electrons, which can significantly contribute to the heating of the interstellar gas. AIMS Our aim is to investigate the impact of molecular size on the photoionization properties of cationic PAHs. METHODS Trapped PAH cations of sizes between 30 and 48 carbon atoms were submitted to VUV photons in the range of 9 to 20 eV from the DESIRS beamline at the synchrotron SOLEIL. All resulting photoproducts including dications and fragment cations were mass-analyzed and recorded as a function of photon energy. RESULTS Photoionization is found to be predominant over dissociation at all energies, which differs from an earlier study on smaller PAHs. The photoionization branching ratio reaches 0.98 at 20 eV for the largest studied PAH. The photoionization threshold is observed to be between 9.1 and 10.2 eV, in agreement with the evolution of the ionization potential with size. Ionization cross sections were indirectly obtained and photoionization yields extracted from their ratio with theoretical photoabsorption cross sections, which were calculated using time-dependent density functional theory. An analytical function was derived to calculate this yield for a given molecular size. CONCLUSIONS Large PAH cations could be efficiently ionized in H i regions and provide a contribution to the heating of the gas by photoelectric effect. Also, at the border of or in H ii regions, PAHs could be exposed to photons of energy higher than 13.6 eV. Our work provides recipes to be used in astronomical models to quantify these points.
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Affiliation(s)
- G. Wenzel
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - C. Joblin
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - A. Giuliani
- Synchrotron SOLEIL, L’Orme des Merisiers, F-91192 Saint Aubin, Gif-sur-Yvette, France
- INRAE, UAR1008, Transform Department, Rue de la Géraudière, BP 71627, F-44316 Nantes, France
| | - S. Rodriguez Castillo
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
- Laboratoire de Chimie et Physique Quantiques (LCPQ/IRSAMC), Université de Toulouse (UPS), CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - G. Mulas
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
- Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (CA), Italy
| | - M. Ji
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
| | - H. Sabbah
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Avenue du Colonel Roche, F-31028 Toulouse, France
- Laboratoire Collisions Agrégats Réactivité (LCAR/IRSAMC), Université de Toulouse (UPS), CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - S. Quiroga
- Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - D. Peña
- Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - L. Nahon
- Synchrotron SOLEIL, L’Orme des Merisiers, F-91192 Saint Aubin, Gif-sur-Yvette, France
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17
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Kerkeni B, Aquino AJA, Berman MR, Hase WL. Structures and binding energies for complexations of different spin states of Ni + and Ni 2+ to aromatic molecules. Mol Phys 2019. [DOI: 10.1080/00268976.2018.1552800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Boutheïna Kerkeni
- Département de Physique, Laboratoire de Physique de la Matière Condensée (LPMC), Faculté des Sciences de Tunis, Université de Tunis El Manar, Tunis, Tunisia
- Institut Supérieur des Arts Multimédia de la, Université de la Manouba, Manouba, Tunisia
- Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, Meudon, France
| | - Adelia J. A. Aquino
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
- School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, People’s Republic of China
| | | | - William L. Hase
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
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West BJ, Lesniak L, Mayer PM. Why Do Large Ionized Polycyclic Aromatic Hydrocarbons Not Lose C2H2? J Phys Chem A 2019; 123:3569-3574. [DOI: 10.1021/acs.jpca.9b01879] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Brandi J. West
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Lukas Lesniak
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Paul M. Mayer
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada K1N 6N5
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Photoprocessing of large PAH cations. ACTA ACUST UNITED AC 2019; 15:388-389. [PMID: 33072171 DOI: 10.1017/s1743921319007063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In cosmic environments, polycyclic aromatic hydrocarbons (PAHs) strongly interact with vacuum ultraviolet (VUV) photons emitted by young stars. Trapped PAH cations ranging in size from 30 to 48 carbon atoms were irradiated by tunable synchrotron light (DESIRS beamline at SOLEIL). Their ionization and dissociation cross sections were determined and compared with TD-DFT computed photoabsorption cross sections. Evidence for radiative cooling is reported.
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Chen FQ, Kono N, Suzuki R, Furukawa T, Tanuma H, Ferrari P, Azuma T, Matsumoto J, Shiromaru H, Zhaunerchyk V, Hansen K. Radiative cooling of cationic carbon clusters, C N+, N = 8, 10, 13-16. Phys Chem Chem Phys 2019; 21:1587-1596. [PMID: 30620033 DOI: 10.1039/c8cp06368k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The radiative cooling of highly excited carbon cluster cations of sizes N = 8, 10, 13-16 has been studied in an electrostatic storage ring. The cooling rate constants vary with cluster size from a maximum at N = 8 of 2.6 × 104 s-1 and a minimum at N = 13 of 4.4 × 103 s-1. The high rates indicate that photon emission takes place from electronically excited ions, providing a strong stabilizing cooling of the molecules.
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Affiliation(s)
- F-Q Chen
- School of Materials Science and Engineering, Tianjin University, Tianjin 300350, China
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21
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Noble JA, Aupetit C, Descamps D, Petit S, Simon A, Mascetti J, Ben Amor N, Blanchet V. Ultrafast electronic relaxations from the S3 state of pyrene. Phys Chem Chem Phys 2019; 21:14111-14125. [DOI: 10.1039/c8cp06895j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The ultrafast relaxation occurring in pyrene upon excitation at 4.68 eV was studied in a supersonic gas-jet fs pump–probe experiment.
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Affiliation(s)
| | | | | | - Stéphane Petit
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107
- F33405 Talence
- France
| | - Aude Simon
- Université de Toulouse-CNRS-UT3, LCPQ-IRSAMC
- F-31062 Toulouse
- France
| | | | - Nadia Ben Amor
- Université de Toulouse-CNRS-UT3, LCPQ-IRSAMC
- F-31062 Toulouse
- France
| | - Valérie Blanchet
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107
- F33405 Talence
- France
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Haitjema J, Wu L, Giuliani A, Nahon L, Castellanos S, Brouwer AM. Photo-induced Fragmentation of a Tin-oxo Cage Compound. J PHOTOPOLYM SCI TEC 2018. [DOI: 10.2494/photopolymer.31.243] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Lianjia Wu
- Advanced Research Center for Nanolithography
| | | | | | | | - Albert M. Brouwer
- Advanced Research Center for Nanolithography
- University of Amsterdam, van’t Hoff Institute for Molecular Sciences
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23
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Castillo SR, Simon A, Joblin C. Investigating the importance of edge-structure in the loss of H/H 2 of PAH cations: the case of dibenzopyrene isomers. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2018; 429:189-197. [PMID: 30186034 PMCID: PMC6120680 DOI: 10.1016/j.ijms.2017.09.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present a detailed study of the main dehydrogenation processes of two dibenzopyrene cation (C24H14+) isomers, namely dibenzo(a,e)pyrene (AE+) and dibenzo(a,l)pyrene (AL+). First, action spectroscopy under VUV photons was performed using synchrotron radiation in the 8-20 eV range. We observed lower dissociation thresholds for the non-planar molecule (AL+) than for the planar one (AE+) for the main dissociation pathways: H and 2H/H2 loss. In order to rationalize the experimental results, dissociation paths were investigated by means of density functional theory calculations. In the case of H loss, which is the dominant channel at the lowest energies, the observed difference between the two isomers can be explained by the presence in AL+ of two C-H bonds with considerably lower adiabatic dissociation energies. In both isomers the 2H/H2 loss channels are observed only at about 1 eV higher than H loss. We suggest that this is due to the propensity of bay H atoms to easily form H2. In addition, in the case of AL+, we cannot exclude a competition between 2H and H2 channels. In particular, the formation of a stable dissociation product with a five-membered ring could account for the low energy sequential loss of 2 hydrogens. This work shows the potential role of non-compact PAHs containing bay regions in the production of H2 in space.
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Affiliation(s)
- Sarah Rodriguez Castillo
- Institut de Recherche en Astrophysique et Planétologie IRAP, Université de Toulouse (UPS), CNRS, CNES, 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France
- Laboratoire de Chimie et Physique Quantiques LCPQ/IRSAMC, Université de Toulouse (UPS) and CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - Aude Simon
- Laboratoire de Chimie et Physique Quantiques LCPQ/IRSAMC, Université de Toulouse (UPS) and CNRS, 118 Route de Narbonne, F-31062 Toulouse, France
| | - Christine Joblin
- Institut de Recherche en Astrophysique et Planétologie IRAP, Université de Toulouse (UPS), CNRS, CNES, 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France
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Jusko P, Simon A, Wenzel G, Brünken S, Schlemmer S, Joblin C. Identification of the fragment of the 1-methylpyrene cation by mid-IR spectroscopy. Chem Phys Lett 2018; 698:206-210. [PMID: 29882538 PMCID: PMC5988045 DOI: 10.1016/j.cplett.2018.03.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The fragment of the 1-methylpyrene cation, C 17 H 11 + , is expected to exist in two isomeric forms, 1-pyrenemethylium PyrCH 2 + and the tropylium containing species PyrC 7 + . We measured the infrared (IR) action spectrum of cold C 17 H 11 + tagged with Ne using a cryogenic ion trap instrument coupled to the FELIX laser. Comparison of the experimental data with density functional theory calculations allows us to identify the PyrCH 2 + isomer in our experiments. The IR Multi-Photon Dissociation spectrum was also recorded following the C2H2 loss channel. Its analysis suggests combined effects of anharmonicity and isomerisation while heating the trapped ions, as shown by molecular dynamics simulations.
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Affiliation(s)
- Pavol Jusko
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France
- I. Physikalisches Institut, Universität zu Käoln, Zülpicher Str. 77, 50937 Köln, Germany
| | - Aude Simon
- Laboratoire de Chimie et Physique Quantiques LCPQ/IRSAMC, Université de Toulouse (UPS) and CNRS, 118 Route de Narbonne, 31062 Toulouse, France
| | - Gabi Wenzel
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France
| | - Sandra Brünken
- I. Physikalisches Institut, Universität zu Käoln, Zülpicher Str. 77, 50937 Köln, Germany
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - Stephan Schlemmer
- I. Physikalisches Institut, Universität zu Käoln, Zülpicher Str. 77, 50937 Köln, Germany
| | - Christine Joblin
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse (UPS), CNRS, CNES, 9 Av. du Colonel Roche, 31028 Toulouse Cedex 4, France
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Bazzi S, Welsch R, Vendrell O, Santra R. Challenges in XUV Photochemistry Simulations: A Case Study on Ultrafast Fragmentation Dynamics of the Benzene Radical Cation. J Phys Chem A 2018; 122:1004-1010. [PMID: 29298485 DOI: 10.1021/acs.jpca.7b11543] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The challenges of simulating extreme ultraviolet (XUV)-induced dissociation dynamics of organic molecules on a multitude of coupled potential energy surfaces are discussed for the prototypical photoionization of benzene. The prospects of Koopmans' theorem-based electronic structure calculations in combination with classical trajectories and Tully's fewest switches surface hopping are explored. It is found that a Koopmans' theorem-based approach overestimates the CH dissociation barrier and thus underestimates the fragmentation yield. However, the nonadiabatic population dynamics are in good agreement with previous approaches, indicating that the Koopmans' theorem based potentials are well described around the Franck-Condon point. This is explicitly tested for the ground state potential of the benzene cation employing CASPT2 calculations, for which very good agreement is found. This work highlights the need for efficient electronic structure approaches that can treat medium-sized organic molecules with a multitude of coupled excited states and several dissociation channels.
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Affiliation(s)
- Sophia Bazzi
- Center for Free-Electron Laser Science, DESY , Notkestrasse 85, 22607 Hamburg, Germany.,Department of Chemistry, University of Hamburg , Grindelallee 117, 20146 Hamburg, Germany
| | - Ralph Welsch
- Center for Free-Electron Laser Science, DESY , Notkestrasse 85, 22607 Hamburg, Germany
| | - Oriol Vendrell
- Center for Free-Electron Laser Science, DESY , Notkestrasse 85, 22607 Hamburg, Germany.,Department of Physics and Astronomy, Aarhus University , Ny Munkegade 120, 8000 Aarhus C, Denmark.,The Hamburg Centre for Ultrafast Imaging , Luruper Chausee 149, 22761 Hamburg, Germany
| | - Robin Santra
- Center for Free-Electron Laser Science, DESY , Notkestrasse 85, 22607 Hamburg, Germany.,Department of Chemistry, University of Hamburg , Grindelallee 117, 20146 Hamburg, Germany.,The Hamburg Centre for Ultrafast Imaging , Luruper Chausee 149, 22761 Hamburg, Germany.,Department of Physics, University of Hamburg , Jungiusstrasse 9, 20355 Hamburg, Germany
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Polycyclic Aromatic Hydrocarbons in Protoplanetary Disks around Herbig Ae/Be and T Tauri Stars. ACTA ACUST UNITED AC 2017. [DOI: 10.3847/1538-4357/835/2/291] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Colliding the hydrocarbon building blocks of astrochemical polycyclic aromatic hydrocarbons with 8 keV He+ and H2+ ions: Luminescence from methane, acetylene, benzene and naphthalene. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2016.11.052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Walsh AJ, Tielens AGGM, Ruth AA. Diamond-like-carbon nanoparticle production and agglomeration following UV multi-photon excitation of static naphthalene/helium gas mixtures. J Chem Phys 2016; 145:024303. [PMID: 27421401 DOI: 10.1063/1.4955192] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the formation of nanoparticles with significant diamond character after UV multi-photon laser excitation of gaseous naphthalene, buffered in static helium gas, at room temperature. The nanoparticles are identified in situ by their absorption and scattering spectra between 400 and 850 nm, which are modeled using Mie theory. Comparisons of the particles' spectroscopic and optical properties with those of carbonaceous materials indicate a sp(3)/sp(2) hybridization ratio of 8:1 of the particles formed. The particle extinction in the closed static (unstirred) gas-phase system exhibits a complex and quasi-oscillatory time dependence for the duration of up to several hours with periods ranging from seconds to many minutes. The extinction dynamics of the system is based on a combination of transport features and particle interaction, predominantly agglomeration. The relatively long period of agglomeration allows for a unique analysis of the agglomeration process of diamond-like carbon nanoparticles in situ.
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Affiliation(s)
- A J Walsh
- Physics Department and Environmental Research Institute, University College Cork, Cork, Ireland
| | - A G G M Tielens
- Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333-CA Leiden, The Netherlands
| | - A A Ruth
- Physics Department and Environmental Research Institute, University College Cork, Cork, Ireland
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