Abstract
The first excited state of at 2.14 Mev emits gamma rays which have an isotropic distribution when excited over a wide range of energy in the reaction and an isotropic correlation in the reaction . The natural assumption is therefore that the state is of spin ½ as is suggested by the shell model. This assignment is supported by certain gamma-ray studies in the reaction . However, in both the reaction and the mirror reaction leading to this level or its mirror level in , an stripping pattern is found, suggesting . The observed isotropies could be given by emission from a state of to the ground state if the gamma ray were purely . In the present investigation it is shown by a Doppler shift method using that the lifetime of the first excited state is less than 4× sec. It is shown that this limit is inconsistent with sum rules and therefore that the transition is chiefly and that the spin of the level must be ½-. This is consistent with the stripping result only if it is possible for the departing nucleon in such a reaction to flip its intrinsic spin and so transmit a further unit of angular momentum to the nucleus.
- Received 2 October 1956
DOI:https://doi.org/10.1103/PhysRev.105.666
©1957 American Physical Society