Abstract
The () reaction has been used to study . Back-scattered protons were detected in an annular solid-state detector of 0.8-sr solid angle. The rays were detected in a 32-cc Ge(Li) detector placed at 55° and 125° with respect to the beam. By the Doppler-shift attenuation method (DSAM) the lifetimes of states in with the following energies have been measured: 2.422 MeV [0.30(+0.04, -0.03) psec]; 2.750 MeV [3.4(+11, -0.17) psec]; 3.250 MeV [0.3(+0.15, -0.10) psec]; 3.297 MeV [ psec]; 3.389 MeV (0.325±0.075 psec); 3.442 MeV [1.35(+1.3, -1) psec]; and 3.651 MeV [0.06(±0.08, -0.06) psec]. The 1.523-MeV state was measured to have a lifetime in close agreement with the known lifetimes. The Doppler shift on the 4.43-MeV state in was also measured. Branching ratios are reported for 14 states. The reduced matrix elements are given for 26 transitions. On the basis of branching-ratio information, , and previously existing information, spin and parity inferences have been made for the following states: 3.250 MeV ();3.297 MeV (, ); 3.883 MeV (, ); and 4.043 MeV (, , ). For other states, we support recent assignments from () data. Our transition rates for the 2.422-MeV (), 2.750-MeV (), and 3.250-MeV () states show strong enhancement over single-particle rates. These results, together with the known enhanced rates for the 1.523-MeV () and 1.836-MeV () states, strongly support the interpretation of the low-lying levels in as mixtures of a rotational band and simple shell-model configurations. The level at 3.250 MeV, () fits naturally into this scheme.
- Received 19 August 1968
DOI:https://doi.org/10.1103/PhysRev.177.1725
©1969 American Physical Society