Coulomb excitation of radioactive 20, 21Na

The low-energy structures of the radioactive nuclei 20, 21Na have been examined using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ∼ 5×106 ions/s were accelerated to 1.7MeV/A and Coulomb excited in a 0.5mg/cm^2 natTi target. Two TIGRESS HPGe clover detectors perpendicular to the beam axis were used for $$ \gamma$$ -ray detection, while scattered nuclei were observed by the Si detector BAMBINO. For 21Na , Coulomb excitation from the 3/2+ ground state to the first excited 5/2+ state was observed, while for 20Na , Coulomb excitation was observed from the 2+ ground state to the first excited 3+ and 4+ states. For both beams, B ( $$ \lambda$$L) values were determined using the 2+$$ \rightarrow$$ 0+ de-excitation in 48Ti as a reference. The resulting B(E2) ↓ value for 21Na is 137±9 e^2fm^4, while the resulting B($$ \lambda$$L) ↓ values for 20Na are 55±6 e^2fm^4 for the 3+$$ \rightarrow$$ 2+ , 35.7±5.7 e^2 fm^4 for the 4+$$ \rightarrow$$ 2+ , and 0.154±0.030 μ_N^2 for the 4+$$ \rightarrow$$ 3+ transitions. This analysis significantly improves the measurement of the 21Na B(E2) value, and provides the first experimental determination of B($$ \lambda$$L) values for the proton dripline nucleus 20Na .-1