Direct detection of the elusive 229thorium isomer: Milestone towards a nuclear clock

Recently, the first direct detection of the long-searched low-lying isomeric first excited state of
²²⁹
Th could be realized via its internal conversion decay branch, which confirms the isomer's existence and lays the foundation for precise studies of its decay parameters, in particular its half-life and excitation energy. Follow-up studies confirmed the theoretically expected lifetime reduction by about 10
⁹
of neutral
^229m
Th compared to charged isomers with τ∼10 μS thus emphasizing the need to efficiently suppress internal conversion when aiming for the detection of a potential photonic decay branch of
^229m
Th. Work towards precisely determining the excitation energy of the thorium isomer is ongoing, preparing for an all-optical control of this potentially highly precise nuclear frequency standard transition.