A Laser Excitation Scheme for 229mTh

Direct laser excitation of the lowest known nuclear excited state in 229Th has been a long-standing objective. It is generally assumed that reaching this goal would require a considerably reduced uncertainty of the isomer’s excitation energy compared to the presently adopted value of (7.8±0.5)eV. Here we present a direct laser excitation scheme for 229mTh, which circumvents this requirement. The proposed excitation scheme makes use of already existing laser technology and therefore paves the way for nuclear laser spectroscopy. In this concept, the recently experimentally observed internal-conversion decay channel of the isomeric state is used for probing the isomeric population. A signal-to-background ratio of better than 104 and a total measurement time of less than three days for laser scanning appear to be achievable.