Towards a precise determination of the excitation energy of the Thorium nuclear isomer using a magnetic bottle spectrometer

Understand

$^{229}$Th is the only known nucleus with an excited state that offers the possibility for a direct laser excitation using existing laser technology.

• Its excitation energy has been measured indirectly to be 7.8(5) eV ($\approx$160 nm).
• The energy and lifetime of the isomeric state make it the presently only suitable candidate for a nuclear optical clock, the uncertainty of the excitation energy is, however, still too large to allow for a direct laser excitation in a Paul trap.
• Therefore, a major goal during the past years has been an improved energy determination.