Isomeric state in the doubly odd At-196 nucleus

An excited isomeric state has been identified in the At-196 nucleus using t he recoil decay tagging technique. This is the first identification of an e xcited state in this neutron-deficient odd-odd nucleus. Several tentative p rompt gamma-rays have also been correlated with At-196 alpha-decay, althoug h it has not been possible to assign them to specific energy levels in At-1 96. The mean lifetime of the isomeric state has been measured as tau = 11 /- 2 mu s. The new level is compared with similar low-lying states in neigh bouring nuclei and is de-excited by an E2 gamma-ray transition, the large h indrance of which is not expected.