HIGH-SPIN STATES IN ²³Na

Abstract

<p>The ¹²C(¹²C,pϒ)²³Na reaction has been used to study the ϒ-ray de-excitation of levels up to Eᵪ = 10.4 MeV in ²³Na. Branching ratios were obtained for the 5.54, 6.11, 6.24 and 6.35 MeV levels and the major modes of decay were observed for 7 levels above Eᵪ = 7 MeV. Doppler-shift attenuation measurements yielded mean lifetimes or lifetime limits for 22 levels in ²³Na. Angular distributions were measured for ϒ rays in coincidence with proton groups corresponding to the 5.54, 6.11, 6.24, 6.35, 9.04 and 10.35 MeV levels. The 6.35 MeV level is assigned a spin and parity of 9/2⁻ and interpreted as a member of the low-lying K^π = 1/2⁻ band in ²³Na. The 5.54 and 6.24 MeV levels are shown to have positive parity and are interpreted as the 11/2⁺ and 13/2⁺ members of the ground-state band, respectively. The highly populated levels at 9.04 and 10.35 MeV are interpreted as the 15/2⁺ and 13/2⁻ members of the groundstate band and K^π = 1/2⁻ band, respectively. The experimental ϒ-ray transition strengths in Na are compared with those predicted by the Nilsson model including band mixing and a modification to the M1 strengths to account for the effects of isospin.</p>