Gamow-Teller (GT) strength distributions were studied in the (p, n ) reaction at 136 MeV on the self-conjugate s-d shell nuclei Ne, Mg, and "Si. The measurements were performed in two separate experiments with the beam-swinger neutron time-of-flight facility at the Indiana University Cyclotron Facility. The flight paths were 91 and 131 m, respectively, for the two experiments. The neutrons were detected in large-volume plastic-scintillation detectors. The overall time resolutions were about 825 ps; this provided energy resolutions from 300 to 400 keV. GT strength was identified as El=0 contributions in transitions to discrete final states and also in the background and continuum. The 0', bi=0 cross sections were converted to B(GT) units using a "universal" conversion formula calibrated to (p, n ) reactions on other even-even s-d shell nuclei. The resulting B(GT) distributions were compared with full s-d shell-model predictions. The distribution for Mg is described well, but the distributions for Ne and Si are described poorly. The total B(GT) strength observed in discrete states (up to 12 MeV of excitation) for each reaction is 65+10 /o of that predicted. If one considers B(GT) strength observed in the continuum above a calculated quasi-free-scattering background, the strength increases to 70 -100% of that predicted.If one considers B(GT) strength in an analysis of the full continuum (up to -20 MeV), the entire amount predicted may be observed. These results are consistent with that observed in other light nuclei.
We report observations from the (p,n) reaction on 12 C at 135 MeV. The experiment was performed with the beam-swinger neutron time-of-flight system at the Indiana University Cyclotron Facility. Neutrons were detected in large-volume plastic scintillation detectors located in three detector stations at 0 • , 24 • , and 45 • with respect to the undeflected beam line; the flight paths were 91 m, 91 m, and 74 m, respectively. Overall time resolutions of about 825 ps provided energy resolutions of about 350 keV in the first two stations and about 425 keV in the third station. The angular distributions for states with excitation energies up to 10 MeV are presented and comparisons are made with DWIA calculations that use one-body density matrices from 0hω and 1hω shell-model calculations. New information is deduced on the excitation energies, widths and spin-parity assignments for several energy levels of 12 N.
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