We present precision Penning trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system, the mass of ⁵¹K was measured for the first time, and the precision of the ^51,52Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, ⁵²Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N force

In this Letter, we report a new mass for 11Li using the trapping experiment TITAN at TRIUMF's ISAC facility. This is by far the shortest-lived nuclide, t_{1/2}=8.8 ms, for which a mass measurement has ever been performed with a Penning trap. Combined with our mass measurements of ;{8,9}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 11Li. This result is a remarkable confluence of nuclear and atomic physics.

Recent high-precision mass measurements of 9 Li and 9 Be, performed with the TITAN Penning trap at the TRIUMF ISAC facility, are analyzed in light of state-of-the-art shell model calculations. We find an explanation for the anomalous Isobaric Mass Multiplet Equation (IMME) behaviour for the two A = 9 quartets. The presence of a cubic d = 6.3(17) keV term for the J π = 3/2 − quartet and the vanishing cubic term for the excited J π = 1/2 − multiplet depend upon the presence of a nearby T = 1/2 state in 9 B and 9 Be that induces isospin mixing. This is contrary to previous hypotheses involving purely Coulomb and charge-dependent effects. T = 1/2 states have been observed near the calculated energy, above the T = 3/2 state. However an experimental confirmation of their J π is needed.PACS numbers: 21.10. Dr,21.10.Hw,27.20.+n Atomic nuclei are described by their binding energy and three quantum numbers: the total angular momentum J, parity π, and isospin T . This framework allows one to identify, each of the ∼ 3000 observed nuclei [1] unambiguously. The isospin quantity is analogous to spin and was first introduced by Heisenberg [2] to describe the charge-independence of the nuclear force. Within the isospin formalism, neutrons (n) and protons (p) are nucleons of isospin T = 1/2 but distinguished by different z-projections T z (n) = 1/2 and T z (p) = -1/2 [2,3]. Nuclei with the same mass number A, total angular momentum and parity form multiplets where the individual members have a projection T z = (N − Z)/2. Assuming isospin is a good quantum number, members of an isobaric multiplet have identical properties. However, Weinberg and Treiman [4] noted that the mass excess ∆ (which is a measure of the nuclear binding energy and defined as the difference between the atomic mass and the atomic mass number) of such nuclides were not identical, but were rather laying along a parabola:where a, b, c are coefficients that depend on all quantum numbers except T z . This so-called isobaric multiplet mass equation (IMME) has proven to be a powerful tool to predict unknown masses. For instance, it is used to obtain masses of nuclei along the rapid proton capture path, where most of the masses are not well known [5] or to provide detailed mass values, which are experimentally inaccessible due to half-life and productions constraints [6]. Recently, the precise mass measurement of 12 Be [7] using the TITAN (TRIUMF Ion Traps for Atomic and Nuclear science) Penning trap mass spectrometer [8,9] has been used as a solid anchor point together with the IMME to address the ambiguous spin assignment of T = 2 states in 12 C and 12 Be.Several tests of the IMME were performed and for most cases, it has followed the original quadratic behaviour [10]. However, in some cases, large deviations were discovered and the incorporation of cubic d(A, T )T [17,18] quintets. The unveiling of the non-quadratic behaviour of the A = 32 and 33 multiplets was only possible due to the precise and accurate mass measurement of some of its members, at the δm/m ∼...