Abstract
Electromagnetic transitions in and have been investigated following the population of the bound levels of these nuclei by +, +, +, and + with bombarding energies from 1.9 to 6.7 MeV. Gamma-ray angular distributions and relative intensities were determined using a three-crystal pair spectrometer. Gamma-ray branching ratios in were determined through measurements of proton-gamma coincidence spectra following the and reactions. The ratios of radiative width to total width for the unbound 10.45- and 10.81-MeV levels of were obtained as and , respectively. Gamma-ray branching ratios in and were determined from measurements of gamma-gamma coincidence spectra using +, +, and +. Evidence was found for an excitation energy for the sixth excited state of of 7.284±0.007 MeV, rather than 7.17±0.05 MeV as previously reported. Singles gamma-ray spectra were measured from all four targets using a lithium-drifted germanium detector. In these measurements, gamma-ray cascades to the 5.3-MeV doublet of were separated, and it was determined that all the bound levels of and except the 5.270- and 5.240-MeV levels have mean lifetimes less than 5× sec. An intermediate-image magnetic spectrometer was used to study the angular correlation of internal pairs for ten ground-state transitions in and . From this work it was determined that the 8.57-MeV level has , the 9.06- and 10.07-MeV levels have , or the 9.76- and 9.93-MeV levels are most probably , and the 9.16-MeV level is most probably . For the remaining levels the measurements serve to restrict the range of possible spin-parity assignments. The correspondence between mirror levels in and is discussed and a comparison with theoretical predictions is made.
- Received 23 July 1965
DOI:https://doi.org/10.1103/PhysRev.140.B1202
©1965 American Physical Society