The nuclear first excited state in Th-229 (called Th-229m) has the lowest excitation energy of all known nuclear states.
The energy of only 7.8(5) eV and its lifetime (in the range of minutes to hours) make it a promising candidate for a nuclear optical clock. The large uncertainty in the excitation energy, however, currently impedes further progress. Therefore the objective of our experiment is a precise determination of the Th-229m excitation energy via internal conversion electron spectroscopy.
The concept and possible applications of a nuclear optical clock as well as a first direct energy measurement will be presented.
