A supersonic beam ion cyclotron resonance instrument for the study of van der Waals cluster ions

For the study of ionized van der Waals cluster ions an instrument is presented, which consists of a supersonic beam cluster source coupled to an ICR spectrometer with external ion source. The neutral van der Waals clusters are generated by supersonic expansion and ionized by electron impact in the external source. The cluster ions are extracted at right angle to the neutral cluster beam and fly collision-free parallel to the magnetic field direction into the differentially pumped ICR cell. For the ion transfer, an improved lens system is presented. The cluster ion transfer lens system is capable of focusing ions with energies of a few eV perpendicular to the magnetic field direction through the differential pumping orifice. The ions are injected into the ICR cell with a trap barrier pulse, ion accumulation is possible. With this system the first ICR spectra of small cluster ions of carbon dioxide are obtained.