An electron impact ionization within radio frequency confinement fields

An electron impact (EI) ion source, comprising:

• a) a RF ion guide having an entrance, an axial centerline, and an axial field to guide ions;
• b) an electron source comprising of a filament generating an electron beam, an electron repeller, and an exit lens, wherein the electron beam is aligned along the axial centerline of the RF ion guide;
• and
• c) a first inlet placed at the entrance of the RF ion guide to introduce analytes, wherein the electron beam is configured to interact with the analytes within RF confinement field to generate an ion beam.

An electron impact (EI) ion source, comprising:

• a) a RF ion guide having an entrance, an axial centerline, and an axial field to guide ions;
• b) an electron source comprising of a filament generating an electron beam, an electron repeller, and an exit lens, wherein the electron beam is aligned along the axial centerline of the RF ion guide;
• c) a first inlet placed at the entrance of the RF ion guide to introduce inert or atomic gases;
• d) a second inlet placed in the RF ion guide to introduce analytes;
• e) wherein the first inlet and the RF ion guide are configured so the inert or atomic gases are ionized by the electron beam creating ionized inert or atomic gases;
• and
• f) wherein the second inlet and RF ion guide are configured so that the analytes are ionized by the ionized inert or atomic gases through an ion/molecular reaction and result in a soft ionization of the analytes.