Charge-exchange collisions between ultracold fermionic ${}^6\mathrm{Li}$ atoms and ${}^{40}\mathrm{Ca}^{+}$ ions are observed in the millikelvin temperature range. The reaction product of the charge-exchange collision is identified via mass spectrometry during which the motion of the ions is excited parametrically. The cross sections of the charge-exchange collisions between ${}^6\mathrm{Li}$ atoms in the ground state and ${}^{40}\mathrm{Ca}^{+}$ ions in the ground and metastable excited states are determined. Investigation of the inelastic collision characteristics in the atom-ion mixture is an important step toward ultracold chemistry based on ultracold atoms and ions.

• Received 17 February 2015

DOI:https://doi.org/10.1103/PhysRevA.91.032709