Postionization of molecules desorbed from surfaces by keV ion bombardment with femtosecond laser pulses

We report the use of femtosecond laser photoionization of sputtered neutral molecules to enhance the sensitivity of detection and to improve the prospects for molecule-specific imaging experiments. Results are presented for patterned metal oxides, polycyclic aromatic hydrocarbons and several amino acids. In addition to increased signal levels, we find that fs photoionization generally yields simpler mass spectra than the corresponding SIMS spectra, although considerable fragmentation is observed in both cases.