On the Direct Detection of 229m Th

This thesis describes the first detection of a nuclear transition that had been sought for 40 years, and marks the essential first step toward developing nuclear clocks.

Atomic clocks are currently the most reliable timekeepers. Still, they could potentially be outperformed by nuclear clocks, based on a nuclear transition instead of the atomic transitions employed to date. An elusive, extraordinary state in thorium-229 seems to be the only nuclear transition suitable for this purpose and feasible using currently available technology. Despite repeated efforts over the past 40 years, until recently we had not yet successfully detected the decay of this elusive state.

Addressing this gap, the thesis lays the foundation for the development of a new, better frequency standard, which will likely have numerous applications in satellite navigation and rapid data transfer. Further, it makes it possible to improve the constraints for time variations of fundamental constants and opens up the field of nuclear coherent control.

Lars von der Wense has studied physics and mathematics at the University of Hamburg, Germany, finishing his diploma in theoretical physics in 2009 before proceeding to a master's course in applied mathematics at the University of Cambridge, UK. In 2011 he started his PhD at the Ludwig-Maximilians- University of Munich in experimental physics, leading to the successful direct detection of the thorium-229 nuclear clock transition, the nuclear state of lowest known energy that had resisted observation for 40 years. This work was published with Nature and elected into the top 10 physics breakthroughs of the year 2016 by Physics World.