Abstract
We have measured excitation functions of the rays resulting from the bombardment of by polarized and unpolarized protons in the energy range MeV with emphasis on identifying dipole decays to the first () and second () excited states in . Resonances in are observed at MeV. The 16.21 and 17.12 MeV resonances in are identified as decays of the states to the 6.05 MeV state in . The measured ratio of reduced strengths is 0.48±0.03 for decays from the 16.21 MeV state and 0.55±0.04 for decays from the 17.12 MeV state. The 18.03 MeV resonance is due to a state in with a strength eV and the 18.98 MeV resonance is due to the stretched particle-hole state with a strength of (0.85±0.10) eV. We determine absolute particle and widths for these states. The width of the 18.98 MeV state, (7.1±3.1) eV, is in agreement with a shell-model calculation. Resonances in are observed at 16.82 and 17.27 MeV and in at 17.88 MeV. The excitation energies and widths of these levels as well as the strengths of the transitions suggest a character for all of the resonances for which capture rays are observed. Correspondences of our resonances to levels in are given. Strong branches for many of these states indicate isospin impurities. We compare widths, including ground-state decays, and allowed transition rates in nuclei with shell model calculations and obtain rough agreement with the experimental results. Additional shell model calculations for and Gamow-Teller decays in the nuclei are presented, which indicate that Gamow-Teller matrix elements are quenched by ∼20% relative to shell model predictions and also relative to the spin part of the matrix elements.
NUCLEAR REACTIONS , , , MeV, measured capture rays to MeV final states. Measured , , . Deduced and resonance strengths. Performed shell model calculations and compared with these and other and Gamow-Teller strengths in nuclei near . Deduced average inhibition of GT matrix elements relative to shell model and to the spin part of matrix elements.
- Received 25 January 1983
DOI:https://doi.org/10.1103/PhysRevC.27.1837
©1983 American Physical Society