A study of low-lying [formula omitted] and T = 2 states in some light nuclei (I)

Abstract

We have employed ( 3He, n) double-stripping reactions to locate low-lying T = 3 2 and T = 2 states in several light nuclei. Accurate values for the excitation energies of these states were obtained using a high-resolution time-of-flight spectrometer. The identifications are based upon the intensities of transitions, upper limits on level widths and spin and parity assignments inferred from the shapes of angular distributions. The following levels were studied: 1. (i) Isospin 3 2 levels in 13N were located at excitation energies of 15.068±0.008 MeV ( Γ < 15 keV), 18.44±0.04 MeV and 18.98±0.02 MeV ( Γ = 40±20 keV) in a study of the 11B( 3He, n) reaction at incident energies up to 13.5 MeV. 2. (ii) Isospin 3 2 levels in 17F were observed at excitation energies of 11.195±0.007 MeV ( Γ < 20 keV), 12.540±0.010 MeV ( Γ < 25 keV) and 13.059±0.009 MeV ( Γ < 25 keV) in a study of the 15N( 3He, n) reaction at incident energies up to 11.9 MeV. 3. (iii) Isospin 3 2 levels in 21Na were observed at excitation energies of 8.99±0.05 MeV and 9.221±0.015 MeV ( Γ < 40 keV) in a study of the 19F( 3He, n) reaction at incident energies up to 10.0 MeV. 4. (iv) The excitation energy of the lowest T = 2 state in 20Ne was measured to be 16.730±0.006 MeV ( Γ < 20 keV) in a study of the 18O( 3He, n) reaction at incident energies up to 9.0 MeV. 5. (v) The excitation energy of the lowest T = 2 state in 24Mg was measured to be 15.441±0.015 MeV ( Γ < 35 keV) in a study of the 22Ne( 3He, n) reaction at incident energies up to 9.5 MeV.