Coulomb excitation of radioactive 20, 21Na (original) (raw)

2009, The European Physical Journal A

The low-energy structures of the radioactive nuclei 20,21 Na have been examined using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ∼ 5 × 10 6 ions/s were accelerated to 1.7 MeV/A and Coulomb excited in a 0.5 mg/cm 2 nat Ti target. Two TIGRESS HPGe clover detectors perpendicular to the beam axis were used for γ-ray detection, while scattered nuclei were observed by the Si detector BAMBINO. For 21 Na, Coulomb excitation from the 3/2 + ground state to the first excited 5/2 + state was observed, while for 20 Na, Coulomb excitation was observed from the 2 + ground state to the first excited 3 + and 4 + states. For both beams, B(λL) values were determined using the 2 + → 0 + de-excitation in 48 Ti as a reference. The resulting B(E2) ↓ value for 21 Na is 137 ± 9 e 2 fm 4 , while the resulting B(λL) ↓ values for 20 Na are 55 ± 6 e 2 fm 4 for the 3 + → 2 + , 35.7 ± 5.7 e 2 fm 4 for the 4 + → 2 + , and 0.154 ± 0.030 μN 2 for the 4 + → 3 + transitions. This analysis significantly improves the measurement of the 21 Na B(E2) value, and provides the first experimental determination of B(λL) values for the proton dripline nucleus 20 Na.