Comparison of the mass spectra of perylene (left panels) and coronene (right panels) for different experimental conditions. In black is the spectrum before the SWIFT pulse and without irradiation, which shows electron induced fragmentation (intensity is scaled by 0.3). In red is the SWIFTed and non-irradiated mass spectrum. The green and yellow traces show the mass spectra, after SWIFT pulse and irradiation, for representative low and high laser energy, respectively.