Time-resolved relaxation and fragmentation of polycyclic aromatic hydrocarbons investigated in the ultrafast XUV-IR regime

J. W.L. Lee, D. S. Tikhonov, P. Chopra, S. Maclot, A. L. Steber, S. Gruet, F. Allum, R. Boll, X. Cheng, S. Düsterer, B. Erk, D. Garg, L. He, D. Heathcote, M. Johny, M. M. Kazemi, H. Köckert, J. Lahl, A. K. Lemmens, D. LoruR. Mason, E. Müller, T. Mullins, P. Olshin, C. Passow, J. Peschel, D. Ramm, D. Rompotis, N. Schirmel, S. Trippel, J. Wiese, F. Ziaee, S. Bari, M. Burt, J. Küpper, A. M. Rijs, D. Rolles, S. Techert, P. Eng-Johnsson, M. Brouard, C. Vallance, B. Manschwetus*, M. Schnell

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, and fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10–100 femtoseconds as a result of beyond-Born-Oppenheimer coupling between the electronic and nuclear dynamics. Here, we investigate three PAH molecules: fluorene, phenanthrene, and pyrene, using ultrafast XUV and IR laser pulses. Simultaneous measurements of the ion yields, ion momenta, and electron momenta as a function of laser pulse delay allow a detailed insight into the various molecular processes. We report relaxation times for the electronically excited PAH*, PAH+* and PAH2+* states, and show the time-dependent conversion between fragmentation pathways. Additionally, using recoil-frame covariance analysis between ion images, we demonstrate that the dissociation of the PAH2+ ions favors reaction pathways involving two-body breakup and/or loss of neutral fragments totaling an even number of carbon atoms.

Original languageEnglish
Article number6107
Pages (from-to)1-11
Number of pages11
JournalNature Communications
Early online date20 Oct 2021
Publication statusPublished - Dec 2021

Bibliographical note

Funding Information:
This work was supported by the ERC Starting Grant ASTROROT, grant number 638027, and the project CALIPSOplus under the grant agreement 730872 from the EU Frame-work Programme for Research and Innovation HORIZON 2020. The experimental parts of this research were carried out at beamline BL1 FLASH at DESY, a member of the Helmholtz Association (HGF). We acknowledge the Max Planck Society for funding the development and the initial operation of the CAMP end-station within the Max Planck Advanced Study Group at CFEL and for providing this equipment for CAMP@FLASH. The installation of CAMP@FLASH was partially funded by the BMBF grants 05K10KT2, 05K13KT2, 05K16KT3, and 05K10KTB from FSP-302. We acknowledge financial support by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement 641789 “Molecular Electron Dynamics investigated by Intense Fields and Attosecond Pulses” (MEDEA), the Clusters of Excellence “Center for Ultrafast Imaging” (CUI, EXC 1074, ID 194651731), the “Advanced Imaging of Matter” (AIM, EXC 2056, ID 390715994) of the Deutsche For-schungsgemeinschaft (DFG), and the Helmholtz Gemeinschaft through the “Impuls-und Vernetzungsfonds”. In addition, the project was supported by The Netherlands Organization for Scientific Research (NWO) and is part of the Dutch Astrochemistry Network (DAN) II (Project No. 648.000.029). S.M., J.L., J.P., and P.E.-J. acknowledge support from the Swedish Research Council and the Swedish Foundation for Strategic Research. The authors are additionally thankful for support from the following funding bodies: the UK EPSRC (M. Brouard and C.V. - EP/L005913/1 and EP/V026690/1; M. Burt - EP/ S028617/1), STFC (PNPAS award and mini-IPS Grant No. ST/J002895/1), the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy (F.Z. - DE-FG02-86ER13491); the National Science Foundation (D. Rolles - PHYS-1753324); and the Helmholtz Initiative and Networking Fund through the Young Investigators Group Program (S.B.). This research was supported in part through the Maxwell computational resources operated at Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.

Publisher Copyright:
© 2021, The Author(s).


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