2010ApJ...708..435P

The interaction of keV ions with polyaromatic hydrocarbons is dominated by charge exchange and electronic stopping. We have studied the response of the polyaromatic hydrocarbon anthracene (C₁₄H₁₀) upon keV H⁺ and He²⁺ impact using high-resolution time-of-flight mass spectrometry. Extensive fragmentation into small C_nH^ q+^_m as well as formation of up to triply charged parent ions is observed. Ab initio electron densities are used to calculate the molecular excitation due to electronic stopping. Fragment yields increase with the increase of electronic stopping as a function of projectile velocity. For equal electronic stopping, He²⁺ is found to induce more fragmentation than H⁺. The difference in fragmentation is concluded to be due to two electron processes, which are relevant channels only for He²⁺.