State-selected ion-molecule reactions with Coulomb-crystallized   molecular ions in traps
  State-selected Coulomb-crystallized molecular ions were employed for the first time in ion-molecule reaction studies using the prototypical charge-transfer process $\mathrm{N_2^++N_2\rightarrow N_2+N_2^+}$ as an example. By preparing the reactant ions in a well-defined rovibrational state and localizing them in space by sympathetic cooling to millikelvin temperatures in an ion trap, state- and energy-controlled reaction experiments with sensitivities on the level of single ions were performed. The experimental results were interpreted with quasi-classical trajectory simulations on a six-dimensional potential-energy surface which provided detailed insight into translation-to-rotation energy transfer occurring during charge transfer between N$_2$ and N$_2^+$. 
Xin Tong, Tibor Nagy, Juvenal Yosa Reyes, Matthias Germann, Markus   Meuwly, Stefan Willitsch
physics.chem-ph physics.atom-ph