Ion source configuration for production of ionized clusters, ionized molecules and ionized mono-atoms

Ion sources and methods for generating molecular ions in a cold operating mode and for generating atomic ions in a hot operating mode are provided. In some embodiments, first and second electron sources are located at opposite ends of an arc chamber. The first electron source is energized in the cold operating mode, and the second electron source is energized in the hot operating mode. In other embodiments, electrons are directed through a hole in a cathode in the cold operating mode and are directed at the cathode in the hot operating mode. In further embodiments, an ion beam generator includes a molecular ion source, an atomic ion source and a switching element to select the output of one of the ion sources.