Coulomb excitation structure studies of neon-21, sodium-20,21.

摘要

The low-energy structures of the radioactive nuclei 20,21Na, and the stable nucleus 21Ne have been examined using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ∼5x10 6 ions/s were accelerated to 1.7 MeV/A and Coulomb excited in a 0.5 mg/cm2 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 B AMBINO. For 21Ne and 21Na, Coulomb excitation from the 3/2+ ground states to the first excited 5/2 + states were observed, while for 20Na, Coulomb excitation was observed from the 2+ ground state to the first excited 3+ and 4+ states. For all beams, B( lambdaL) values were determined using the 2+ → 0+ de-excitation in 48Ti as a reference. The resulting B(E2)↓ value for 21Ne is 87.5+/-5.8 e2fm4, for 21Na B(E2)↓ =137+/-9 e 2fm4, while the resulting B( lambdaL)↓ values for 20Na are 55+/-6 e 2fm4 for the 3+ → 2+, 35.7+/-5.7 e2fm4 for the 4+ → 2+, and 0.154+/-0.030 microN 2 for the 4+ → 3+ transitions. This analysis significantly improves the measurement of the 21Na B(E2; 5/2+ → 3/2+) value, improves the precision of this same transition in 21Ne, and provides the first experimental determination of B( lambdaL) values for the proton-dripline nucleus 20Na.