Fast ion beams reveal structures of molecular ions

Of the many ionic species that normally emerge from the ion source of an electrostatic accelerator, it has traditionally been only the monatomic ions that are considered to provide “useful” beams. The remaining beams of molecular ions (⁠$H2+,$ $H3+,$ $HeH+,$ $OH+,$ etc.), which frequently constitute as much as 90% of the total ion‐beam current, are seldom used in a nuclear‐physics experiment.