Proton pick-up from the magnesium isotopes: 24, 25, 26Mg(d, τ)23, 24, 25Na

Abstract

Abstract Energy spectra and angular distributions of the 3He particles from the (d, τ) reaction on 24, 25, 26Mg have been measured at Ed = 52 MeV with an energy resolution of about 80 keV. Excited states up to 11 MeV have been observed in 23Na. High-lying l = 1 transitions were excited by pick-up from the 1 p 3 2 shell. Discrepancies of 1p proton separation energies determined by quasi-free scattering and proton pick-up are discussed. The l-values have been determined for transitions to a variety of states with unknown spins in the doubly odd 24Na nucleus. A spin 5+ can be attributed to the 1.51 MeV level which is then the second member of the 4+ ground state rotational band. Several previously unknown spins could be determined in the 25Na level scheme. There is an apparent similarity in the proton-hole spectra of 23Na and 25Na and consequently a similar rotational structure. The spectra of 23Na, 24Na and 25Na are discussed in the framework of the Nilsson model. The spectroscopic factors are compared with shell-model calculations and predictions from a simple rotational model. States which are excited by pick-up from Nilsson orbit no. 7 contain approximately 75 % of the total sd strength. This contradicts the rotational model and requires strong band mixing. On the other hand the shell-model calculations account for excitation energies and spectroscopic factors of low-lying positive parity states. The data provide information about T = 1 and T = 3 2 states in mass-24 and mass-25 nuclei respectively.