Coulomb excitation of the proton-dripline nucleus Na20

The low-energy structure of the proton dripline nucleus Na20 has been studied using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. A 1.7-MeV/nucleon Na20 beam of ~5×106 ions/s was Coulomb excited by a 0.5-mg/cm2 natTi target. Scattered beam and target particles were detected by the BAMBINO segmented Si detector while γ rays were detected by two TIGRESS HPGe clover detectors set perpendicular to the beam axis. Coulomb excitation from the 2+ ground state to the first excited 3+ and 4+ states was observed, and B(λL) values were determined using the 2+→0+ de-excitation in Ti48 as a reference. The resulting B(λL)↓ values are B(E2;3+→2+)=55±6 e2fm4 (17.0±1.9 W.u.), B(E2;4+→2+)=35.7±5.7 e2fm4 (11.1±1.8 W.u.), and B(M1;4+→3+)=0.154±0.030 μN2 (0.086±0.017 W.u.). These measurements provide the first experimental determination of B(λL) values for this proton dripline nucleus of astrophysical interest.