Atomic hydrogen interactions with gas-phase coronene cations: hydrogenation versus fragmentation

Area of Science:

• Physical Chemistry
• Astrochemistry
• Computational Chemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are prevalent in interstellar environments.
• Hydrogenation of PAH cations is a key process in astrochemistry.
• Understanding PAH fragmentation is crucial for interpreting astronomical observations.

Purpose of the Study:

• To investigate the fragmentation pathways of coronene cations upon sequential hydrogenation.
• To elucidate the role of energy distribution in PAH fragmentation.
• To compare experimental results with computational simulations.

Main Methods:

• Tandem mass spectrometry was used to study hydrogen attachment to gas-phase coronene cations.
• Molecular dynamics simulations with density functional based tight binding (DFTB) were employed.
• Analysis of C2Hi loss and multifragmentation as de-excitation channels.

Main Results:

• Increasing hydrogenation leads to structural changes from planar to puckered and aromatic to aliphatic.
• C2Hi loss and multifragmentation were identified as primary fragmentation channels.
• Simulations accurately reproduced experimental fragmentation patterns when realistic energy distributions were considered.

Conclusions:

• The fragmentation of hydrogenated coronene cations is sensitive to the energy deposited during hydrogenation and subsequent cooling.
• Computational modeling, when incorporating realistic energy distributions, provides a reliable method for studying PAH fragmentation.
• This work enhances our understanding of chemical evolution in interstellar media.