Gas phase photoabsorption and mass spectra of l-alanine and l-proline in the soft X-ray region

We report on new soft X-ray photoionization studies of the amino acids l-alanine and l-proline. Total ion yield and mass spectra have been obtained in gas phase, around the N 1s and O 1s edges, using Time-of-Flight Mass Spectrometry and synchrotron radiation as excitation source. No site selectivity was observed in the ionic dissociation of the molecules. The ionic species have been assigned and a qualitative fragmentation mechanism has been proposed.