Efficient associative ionization of ultracold lithium and the long-lived Li2+

Abstract

We report on the efficient production of Li+ 2 ions in a magneto-optical trap (MOT) of Li atoms prepared in an ensemble of 2⁢𝑆, 2⁢𝑃, and 3⁢𝑆 states. A linear Paul trap surrounding the MOT is used to trap and investigate the time evolution of the ion populations. Associative ionization of Li(2⁢𝑃3/2) and Li(3⁢𝑆1/2) atoms, with a giant cross section of ∼2.2×106\(\sim 2.2 \times 10^6 \, a_0^2\) , is the dominant Li+ 2 production channel. Li+ 2 decays to Li+ via photodissociation and also in the absence of light, which are investigated experimentally and theoretically. A fraction of the Li+ 2 ions are long-lived in the presence of the MOT light, implying that they are deeply bound and hence immune to dissociation, which opens up the possibility for studying Li+ 2 molecular ion interactions with alkali atoms.