Prompt and delayed spectroscopy of199At

Abstract

The neutron-deficient nucleus199At has been studied through γ -ray and electron spectroscopy, using the recoil-decay tagging technique. Two experiments were conducted, using a gas-filled recoil separator with a focal-plane spectrometer alone and together with a germanium-detector array at the target position. The resulting level scheme for 199At includes a new isomer with a half-life of 0.80(5) μs and a spin and parity of (29/2+). The 13/2+ isomer, which de-excites via an M2 transition to the 9/2- ground state, was measured to have a half-life of 70(20) ns. Our earlier version of the level scheme for 197At has been updated as well. © 2010 The American Physical Society.