  The generation of organic particle beams is studied in combination with
photoionization using uv radiation at 266 nm and vuv light at 157 nm.
Single-photon ionization with pulsed vuv light turns out to be sensitive enough
to detect various large neutral biomolecular complexes ranging from metal-amino
acid complexes to nucleotide clusters and aggregates of polypeptides. Different
biomolecular clusters are shown to exhibit rather specific binding
characteristics with regard to the various metals that are co-desorbed in the
source. We also find that the ion signal of gramicidin can be increased by a
factor of fifteen when the photon energy is increased from 4.66 eV to 7.9 eV.
