Abstract
The level structure and the decay properties of the levels in up to 4082 keV of excitation have been carefully investigated via prompt and coincidence experiments employing Ge(Li) -ray detectors and annular Si surface-barrier charged-particle detectors. From these experiments and from high-resolution singles energy and directional- correlation measurements an improved decay scheme has been obtained which includes 44 levels in and incorporates 120 rays. New levels at 2584.5, 3739.4, 3942.4, and 4081.8 keV were postulated, while the decay of several previously reported levels between 3277-3802 keV was not observed. The singles directional correlations from many transitions were used to obtain (i) reliable branching ratios for the more intense rays and (ii) multipole mixing ratios by employing both a ratio method and an independent analysis of the correlations via the compound statistical theory of nuclear reactions. Branching ratios for the weaker rays were obtained from spectra taken at 55° to the beam direction. The lifetimes of 31 levels in were measured by the Doppler-shift attenuation method via the reaction at bombardment energies between 9.7 and 12.2 MeV. Lifetimes were extracted from singles spectra obtained at 0, 15, 30, 45, 70, 90, and 110° and from coincidence spectra obtained at 0° to the beam direction, by employing both a centroid shift analysis for the data from all angles and a line-shape fitting analysis for the data from angles ≤45°. The stopping power of Ni previously calibrated for Cu ions, was used for the line-shape analysis and for obtaining reliable curves applicable to the present conditions of both the singles and the coincidence experiments. For a large number of transitions in values for and were obtained. The and values together with the values and the branching ratios from the first 10 levels in are compared with recent detailed calculations for based on a unified model. Good general agreement is observed between experiment and theory for the values. Only moderate agreement between experiment and theory is observed for the and values.
- Received 12 March 1973
DOI:https://doi.org/10.1103/PhysRevC.8.629
©1973 American Physical Society