Investigation of the low-lying isomer in 229Th by collinear laser spectroscopy

A new ion beam of 229Th is available at the Jyvaesklyae IGISOL facility, produced from the α decay of 233U. A small branching ratio (∼ 2%) is believed to populate the inferred low-lying (5.5 eV) isomeric state in 229Th. A laser ionization scheme is currently being developed to improve the yield of 229Th from the source. The ion source uses a novel electric field configuration for fast and efficient extraction of α-recoils and is able to provide beams of short lived (τ≥ 30 ms) radioactive nuclei. Identification of the isomeric state by collinear laser spectroscopy will reduce the lower lifetime limit of the state and provide the first direct evidence for its existence.