Ion generation in mass spectrometers by cluster bombardment

摘要

The invention relates to the generation of ions of heavy molecules, especially biomolecules, in mass spectrometers by bombarding them with uncharged clusters of molecules. The analyte ions 6 which are released by the cluster bombardment of analyte substances on the surface of a sample support plate 5 show a broad distribution of kinetic energies, which prevents good ion-optical focusing. In the invention, kinetic energies are homogenized in a higher-density collision gas 15, preferably provided in an RF ion guide, and more preferably in an RF ion funnel 7, which can transfer the ions to the mass analyser. The collision gas 15 may be introduced with temporal pulsing, coordinated or synchronized with the pulsed supersonic gas jet 4 which delivers the neutral clusters, and may be pumped off again before the next supersonic gas pulse. In an advantageous embodiment, the collision gas can originate from the supersonic gas jet itself.