A study of ²⁷Mg by means of the ²⁶Mg(d, pγ)²⁷Mg reaction

Abstract

The low-lying excited states of ²⁷Mg have been studied by means of ²⁶Mg(d, pγ)²⁷Mg angular correlation measurements at deuteron bombarding energies of 3.00, 3.37 and 4.28 MeV. Analysis by plane wave stripping theory led to assignments $\text{J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{+}}\text{,}\text{5}\text{2}{}^{\mathrm{+}}\text{, (}\text{5}\text{2}{}^{\mathrm{+}}\text{),}\text{3}\text{2}{}^{\mathrm{-}}\text{and}\text{(}\text{3}\text{2}{}^{\mathrm{+}}\text{)}$ for the states of ²⁷Mg at 0.984, 1.69, 1.94, 3.56 and 3.76–3.78 MeV, respectively. Rough values for the multipole-mixing parameter δ of the gamma rays were deduced. Analysis of the results, using the extreme single-particle collective model suggests that ²⁷Mg is a prolate spheroid with a nuclear deformation η ≈ 2. The ground state is assumed to occupy Nilsson orbit 9, and the 0.984 and 1.95 MeV levels are assumed to be the second and third members of the rotational band based on the ground state. A consistent set of model parameters have been determined which give reasonable agreement with the observed energy spacings, branching ratios, multipole-mixing parameters and with previously measured spectroscopic factors. The 1.69 MeV state is conjectured to be a state formed by core excitation.