ONE-STEP ENERGY SCANNING OF WIDE LOW-LYING 1- RESONANCES IN C-13+P AND N-13+P SCATTERING

Thick polyethylene targets have been bombarded with 8.2 MeV C-13 and N-13 beams accelerated by a cyclotron, i.e. having a relatively large energy spread of about 200 keV. Recoil protons have been detected in order to observe the J(pi) = 1- wide resonances at E* = 8.06 and 5.17 MeV in the N-14 and O-14 compound nuclei, respectively. It is shown that accurate values of the energy, width and spin of the resonant states can be obtained under experimental conditions which, at first glance, may seem inappropriate. The method is well suited for resonance studies using radioactive beams. The measured width of the N-14 resonance (GAMMA = 33.7 +/- 1.0 keV) disagrees with a recent measurement (GAMMA = 23 keV). The energy of the O-14 resonance was determined to be E(c.m) = 526 +/- 3 keV instead of 545 +/- 10 keV as quoted in the literature. A new parameter-free microscopic calculation was undertaken to solve an apparent discrepancy between the experimental proton width and a previous calculation.