In this Letter, we report a new mass for ${}^{11}\mathrm{Li}$ using the trapping experiment TITAN at TRIUMF’s ISAC facility. This is by far the shortest-lived nuclide, $t_{1/2}=8.8\mathrm{ms}$, for which a mass measurement has ever been performed with a Penning trap. Combined with our mass measurements of ${}^{8,9}\mathrm{Li}$ we derive a new two-neutron separation energy of 369.15(65) keV: a factor of 7 more precise than the best previous value. This new value is a critical ingredient for the determination of the halo charge radius from isotope-shift measurements. We also report results from state-of-the-art atomic-physics calculations using the new mass and extract a new charge radius for ${}^{11}\mathrm{Li}$. This result is a remarkable confluence of nuclear and atomic physics.

• Received 21 July 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.202501