Lifetimes of Excited States of the Lanthanum Negative Ion

The negative ion of lanthanum has one of the richest bound state spectra observed for an atomic negative ion and it has been proposed as a promising candidate for laser cooling, which has not yet been achieved for atomic negative ions. In the present experiments, the radiative lifetimes of low-lying bound excited states of La^- were measured at the DESIREE cryogenic electrostatic storage ring facility at Stockholm University. La^- ions were injected into the ring and the populations of ground-state and excited ions were monitored over storage times of up to 800 s using state-selective photodetachment. The results test theoretical predictions of the transition rates and provide insights into the potential of La^{​​​​​​​-} for laser cooling.