Charge-exchange collisions between ultracold fermionic lithium atoms and calcium ions

Charge-exchange collisions between ultracold fermionic Li-6 atoms and Ca-40(+) 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 Li-6 atoms in the ground state and Ca-40(+) 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.