September 12 2018: Atomic hydrogen interactions with gas-phase coronene cations: hydrogenation versus fragmentation
In a fruitful collaboration between theory (Mathias Rapacioli and Aude Simon from University of Toulouse) , astronomy (Stephanie Cazaux, Delft Universty of Technology) and experiments (our team here at the Zernike Institute), we have studied the response of trapped gas-phase coronene cations upon interaction with hydrogen atoms. The results have just been published in PCCP and are hightlighted on the journal cover, which shows an artist impression of the H-induced dissociation of a coronene cation.
Sequential hydrogenation of polycyclic aromatic hydrocarbon (PAH) cations drives a gradual transition from a planar to a puckered geometry and from an aromatic to an aliphatic electronic structure. The resulting H-induced weakening of the molecular structure together with the exothermic nature of the consecutive H-attachment processes can lead to substantial molecular fragmentation. We have studied H attachment to gas-phase coronene cations in a radiofrequency ion trap using tandem mass spectrometry. With increasing hydrogenation, C2Hi loss and multifragmentation are identified as main de-excitation channels. To understand the dependence of both channels on H-exposure time, we have simulated the molecular stability and fragmentation channels of hydrogenated PAHs using a molecular dynamics approach employing potential energies determined by a density functional based tight binding method. As the coronene fragmentation patterns depend on the balance between energy deposition by H-attachment and the extent of cooling in between subsequent attachment processes, we investigate several scenarios for the energy distribution of hydrogenated PAHs. Good agreement between experiment and simulation is reached, when realistic energy distributions are considered.
|Last modified:||12 September 2018 4.30 p.m.|