An X-ray spectroscopy study of structural stability of superhydrogenated pyrene derivatives

Yining Huo, Mónica Espinoza Cangahuala, Vicente Zamudio-Bayer, Marcelo Goulart, Markus Kubin, Martin Timm, J Tobias Lau, Bernd von Issendorff, Ronnie Hoekstra, Shirin Faraji, Thomas Schlathölter*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

3 Citations (Scopus)
41 Downloads (Pure)

Abstract

The stability of polycyclic aromatic hydrocarbons (PAHs) upon soft X-ray absorption is of crucial relevance for PAH survival in X-ray dominated regions (XDRs). PAH stability depends on molecular size but also on the degree of hydrogenation that is related to H2 formation in the interstellar medium (ISM). In this project, we intend to reveal the changes of electronic structure caused by hydrogenation and the impact of hydrogenation on the stability of the carbon backbone for cationic pyrene and its hydrogenated derivatives by analysis of near C K-edge soft X-ray photoions. In our experiments, the PAH cations were trapped in a cryogenic radiofrequency (RF) linear ion trap and exposed to monochromatic X-rays with energies from 279 eV to 300 eV. The photo-products were mass-analyzed by means of time-of-flight (TOF) spectroscopy. Partial ion yields (PIYs) were then studied as a function of photon energy. X-ray absorption spectra computed by time-dependent density functional theory (TD-DFT) aided the interpretation of the experimental results. A very good agreement between experimental data and TDDFT with short-range corrected (SRC) functionals for all PAH ions was reached. The near-edge X-ray absorption mass spectra (NEXAMS) exhibit clear peaks due to C 1s transitions to singly occupied molecular orbitals SOMO and to low-lying unoccupied molecular orbitals. In contrast to coronene cations, where hydrogen attachment drastically increases photostability of coronene, the influence of hydrogenation on photostability is substantially weaker for pyrene cations. Here, hydrogen attachment even destabilizes the molecular structure. An astrophysical model describes the half-life of PAH ions in interstellar environments.
Original languageEnglish
Article number11
Pages (from-to)865-875
JournalMonthly Notices of the Royal Astronomical Society
Volume523
Issue number1
Early online date8-May-2023
DOIs
Publication statusPublished - Jul-2023

Fingerprint

Dive into the research topics of 'An X-ray spectroscopy study of structural stability of superhydrogenated pyrene derivatives'. Together they form a unique fingerprint.

Cite this