Coulomb excitation of the proton-dripline nucleus Na-20

The low-energy structure of the proton dripline nucleus 20 Na has been studied using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. A 1.7-MeV/nucleon 20 Na beam of ∼5 x 10 6 ions/s was Coulomb excited by a 0.5-mg/cm 2 nat Ti 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 48 Ti as a reference. The resulting B(λL)↓ values are B(E2; 3 + → 2 + ) = 55 ± 6e 2 fm 4 (17.0 ± 1.9 W.u.), B(E2; 4 + → 2 + ) = 35.7 ± 5.7 e 2 fm 4 (11.1 ± 1.8 W.u.), and B(M1;4 + → 3 + ) = 0.154 ± 0.030 μ N 2 (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.