Generation of neutral, mass-selected cluster beams

The generation of a neutral, mass-selected cluster beam is demonstrated for the first time. For this purpose positively charged, mass-separated cluster ions were neutralized by electron transfer. We show how dissociation associated with the charge exchange can be detected without ionization and how such processes can be avoided by properly choosing the experimental parameters. The neutral beam with clusters of a single size has a flux of 105 to 106/s and provides an excellent basis for new experiments on clusters under well-defined conditions