Freiburg 2024 – scientific programme
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MO: Fachverband Molekülphysik
MO 3: Novel Spectroscopies
MO 3.7: Talk
Monday, March 11, 2024, 18:30–18:45, HS 1015
VUV Photoionization spectroscopy of cyano-substituted PAHs — •Madhusree Roy Chowdhury1,2, Gustavo Garcia2, Helgi Hrodmarsson3, Jean-Christophe Loison4, and Laurent Nahon2 — 1Institute of Physics and CINSaT, University of Kassel, Kassel, 34132, Germany — 2Synchrotron SOLEIL, L'Orme des Merisiers, Départementale 128, 91190 Saint Aubin, France — 3LISA Laboratory, Universités Paris Est-Paris Diderot-Paris 7, UMR CNRS 7583, Créteil, France — 4Université Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, Talence F-33400, France
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the interstellar medium (ISM), accounting for about a quarter of the total carbon mass of the ISM. The aromatic infrared emission bands (AIBs) are the signatures of the existence of PAHs in the ISM. Although their presence is well acknowledged, the individual detection of PAHs is notoriously difficult. Substituted PAHs being less symmetric are promising candidates, leading to the detection of the two isomers of cyanonaphthalenes (McGuire et.al. Science 2021) in TMC-1. Upon absorbing the VUV radiation, PAHs relax via photoionization and photodissociation processes in competition with radiative cooling. The VUV photoionization and fragmentation of 1- and 2-cyanonaphthalenes is studied using a double imaging photoelectron photoion coincidence spectrometer (i2PEPICO). The KE distribution of the photoelectrons is useful to model the photoelectric heating for radiation fields while the state-selected fragmentation of the cations shed light on the photostability of the cyano substituted PAHs.
Keywords: photoionization; cyanonaphthalenes; electron KE distribution; dissociative ionization; photoelectric gas heating