Knowledge Bank

We have observed the first state-to-state resonant electronic spectrum of $Ne2+$. We use an ion-beam technique to study the ion, in which a nozzle beam of neutral neon molecules is ionised by an electron beam and the resulting molecular ion beam is studied by microwave spectroscopic methods. This ionisation technique results in significant population of the near-dissociation levels of the molecular ion, so that a sensitive state-selective electric field dissociation method can be used to detect the spectra. 68 transitions have been observed spanning the frequency range 6-170Ghz, both single photon and by a microwave-microwave double resonance technique. We have measured the Zeeman splitting produced by small axial magnetic field for many of the lines, which enables us to determine the values of the total angular momentum $J$ involved in each transition and also the effective g factors for the two levels involved. Using this information and that from double-resonance experiments, we have begun to construct an experimental energy level diagram for the molecule. The measured g factors suggest that the description of $Ne2+$ lies somewhere between Hund#### cases ( c ) and (e).