Alternative approach to populate and study the ^229 Th nuclear clock isomer

Abstract

A new approach to observe the radiative decay of the ^229 Th nuclear isomer, and to determine its energy and radiative lifetime, is presented. Situated at a uniquely low excitation energy, this nuclear state might be a key ingredient for the development of a nuclear clock or a nuclear laser and, the search for time variations of fundamental constants like the fine structure constant. The isomer's gamma decay towards the ground state will be studied with a high-resolution vacuum ultraviolet (VUV) spectrometer after its production by the beta decay of ^Ac 229. The novel production method presents a number of advantages asserting its competitive nature with respect to the commonly used ^U 233 alpha-decay recoil source. In this paper, a feasibility analysis of this new concept, and an experimental investigation of its key ingredients, using a pure ^Ac 229 ion beam produced at the ISOLDE radioactive beam facility, is reported.