Spectroscopy of 201At including the observation of a shears band and the 29/2+ isomeric state

The excited states of At-201 were studied and an isomeric 29/2(+) state [T-1/2 = 3.39(9) mu s] was identified by using a fusion-evaporation reaction, a gas-filled recoil separator, and recoil gating techniques. The 29/2(+) state is suggested to originate from the pi(h(9/2)) circle times vertical bar Po-200; 11(-)> configuration, and it decays through the 269-and 339-keV E2-and E3-type transitions, respectively. Moreover, a cascade of magnetic dipole transitions that is suggested to originate from a shears band was observed by using recoil-gated gamma- gamma(-gamma) coincidence techniques.