Destroy, create, transform and sublimate: laboratory dissociation studies on polycyclic aromatic hydrocarbons and analogues

Kamer, J. (2025)

Doctoral Thesis

The aromatic infrared bands (AIBs) seen throughout the interstellar medium (ISM) are generally thought to be carried by polycyclic aromatic hydrocarbons (PAHs) and their nitrogen analogues (PANHs). However, there are still many unanswered questions regarding PA(N)Hs their stability, dissociation behavior, and astrochemical roles. This thesis examines the photoprocessing of PA(N)Hs using a combination of computational modeling, ion trap experiments, synchrotron photoionization, and laboratory spectroscopy. Chapter 3 reports threshold photoelectron spectroscopy and dissociative photoionization of benzonitrile, revealing fragmentation pathways relevant to the formation of complex organic molecules (COMs). Chapter 4 shows that the mid-infrared spectra of PANHs have strong correspondence with AIB features, and Chapter 5 demonstrates that their dissociation results in nitrogen-bearing fragments similar to already observed cyanopolyynes. Chapter 6 explores the reactivity of PAH fragments with water, introducing their role in bottom-up formation pathways. Finally, chapter 7 identifies isomers of doubly dehydrogenated naphthalene cations, showing that molecular hydrogen loss leads to five-membered ring formation.

• Threshold Photoelectron Spectroscopy
• Infrared Multi Photon Dissociation
• Resonant Ejection
• Polycyclic Aromatic Hydrocarbons
• Density Functional Theory
• Ion Trap Experiments
• Aromatic Infrared Bands
• Photodissociation

• All authors: Kamer, J.
• Supervisor: Tielens, A.G.G.M.; Linnartz, H.V.J.
• Co-supervisor: Bouwman, J.
• Committee: Snellen, I.A.G.; Viti, S.; Duncan, M.A.; Kaiser, R.I.; Brünken, S.; Candian, A.
• Qualification: Doctor (dr.)
• Awarding Institution: Leiden Observatory, Faculty of Science, Leiden University
• Date: 2025-10-22
• ISBN (print): 9789464964530