Threshold Energies for Single-Carbon Knockout from Polycyclic Aromatic Hydrocarbons M. H. Stockett M. Gatchell T. Chen N. de Ruette L. Giacomozzi M. Wolf H. T. Schmidt H. Zettergren H. Cederquist 10.1021/acs.jpclett.5b02080.s001 https://acs.figshare.com/articles/journal_contribution/Threshold_Energies_for_Single_Carbon_Knockout_from_Polycyclic_Aromatic_Hydrocarbons/2006028 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 10<sup>5</sup> eV. The shapes of the knockout cross sections are well-described by a simple analytical expression yielding experimental and MD threshold energies of <i>E</i><sub>th</sub><sup>Exp</sup> = 32.5 ± 0.4 eV and <i>E</i><sub>th</sub><sup>MD</sup> = 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 <i>T</i><sub>disp</sub><sup>SE</sup> = 23.3 ± 0.3 eV and <i>T</i><sub>disp</sub><sup>MD</sup> = 27.0 ± 0.3 eV. The semiempirical results compare favorably with measured displacement energies for graphene (<i>T</i><sub>disp</sub> = 23.6 eV). 2015-12-17 10:44:08 PAH molecules energy transfers 23.6 eV knockout threshold energies Polycyclic Aromatic HydrocarbonsWe 0.3 MD displacement energies displacement energies threshold energies MD threshold energies threshold Energies 105 eV SE