Ions colliding with clusters of fullerenes—Decay pathways and covalent bond formations

The Journal of Chemical Physics

Stockett

et al. 2014

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We present scaling laws for absolute cross sections for non-statistical fragmentation in collisions between Polycyclic Aromatic Hydrocarbons (PAH/PAH(+)) and hydrogen or helium atoms with kinetic energies ranging from 50 eV to 10 keV. Further, we calculate the total fragmentation cross sections (including statistical fragmentation) for 110 eV PAH/PAH(+) + He collisions, and show that they compare well with experimental results. We demonstrate that non-statistical fragmentation becomes dominant for large PAHs and that it yields highly reactive fragments forming strong covalent bonds with atoms (H and N) and molecules (C6H5). Thus nonstatistical fragmentation may be an effective initial step in the formation of, e.g., Polycyclic Aromatic Nitrogen Heterocycles (PANHs). This relates to recent discussions on the evolution of PAHNs in space and the reactivities of defect graphene structures.

Section: Discussionmentioning

confidence: 99%

Absolute fragmentation cross sections in atom-molecule collisions: Scaling laws for non-statistical fragmentation of polycyclic aromatic hydrocarbon molecules

Chen

The Journal of Chemical Physics

Stockett

et al. 2014

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“…Recently it has been shown that keV ions colliding with loosely bound clusters of PAHs or fullerenes can induce molecular growth within these clusters [25][26][27][28][29] . This growth is mainly driven by the prompt fragmentation of molecules in cluster when the impacting projectile ion deposits a large amount of energy and momentum to individual atoms through nuclear scattering processes 29 .…”

Section: Introductionmentioning

confidence: 99%

Ion-induced molecular growth in clusters of small hydrocarbon chains

Phys. Chem. Chem. Phys.

Delaunay

D’Angelo

et al. 2017

We report on studies of collisions between 3 keV Ar projectile ions and neutral targets of isolated 1,3-butadiene (CH) molecules and cold, loosely bound clusters of these molecules. We identify molecular growth processes within the molecular clusters that appears to be driven by knockout processes and that could result in the formation of (aromatic) ring structures. These types of reactions are not unique to specific projectile ions and target molecules, but will occur whenever atoms or ions with suitable masses and kinetic energies collide with aggregates of matter, such as carbonaceous grains in the interstellar medium or aerosol nanoparticles in the atmosphere.

“…Knockout fragmentation of C 60 was first reported by Larsen et al, 27 with additional work carried out by Tomita et al 28 In both experiments, 27,28 + inside clusters of fullerene molecules bombarded by keV ions. [30][31][32][33] These earlier studies with PAHs and C 60 have all emphasized that experimental detection of knockout fragments depends sensitively on the internal energy remaining in the large molecular fragment (see Equation 1). Close collisions leading to single-carbon knockout often lead to internal energies suffcient for secondary statistical fragmentation 34 -depleting the unique experimental signal (C-loss for fullerenes; CH x -loss for PAHs) for carbon knockout.…”

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confidence: 99%

Threshold Energies for Single-Carbon Knockout from Polycyclic Aromatic Hydrocarbons

Stockett

Chen

et al. 2015

J. Phys. Chem. Lett.

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We have measured absolute cross sections for ultrafast (femtosecond) single-carbon knockout from polycyclic aromatic hydrocarbon (PAH) cations as functions of He–PAH center-of-mass collision energy in the 10–200 eV range. Classical molecular dynamics (MD) simulations cover this range and extend up to 105 eV. The shapes of the knockout cross sections are well-described by a simple analytical expression yielding experimental and MD threshold energies of EthExp = 32.5 ± 0.4 eV and EthMD = 41.0 ± 0.3 eV, respectively. These are the first measurements of knockout threshold energies for molecules isolated in vacuo. We further deduce semiempirical (SE) and MD displacement energies, i.e., the energy transfers to the PAH molecules at the threshold energies for knockout, of TdispSE = 23.3 ± 0.3 eV and TdispMD = 27.0 ± 0.3 eV. The semiempirical results compare favorably with measured displacement energies for graphene (Tdisp = 23.6 eV).