Atom Trap Trace Analysis (ATTA) is an extremely sensitive trace analysis method developed by Argonne National Lab (ANL). ATTA is used on long-lived, stable radioisotopes such as,, and . By using a laser that is locked to an atomic transition, a CCD or PMT will detect the laser induced fluorescence to allow highly selective, parts-per-trillion to parts-per-quadrillion concentration measurement with single atom detection.[1] This method is useful for atomic transport processes, such as in the atmosphere, geological dating, as well as noble gas purification.[2]
ATTA measurements are possible only if the atoms are excited to a metastable state prior to detection. The main difficulty to accomplishing this is the large energy gap (10-20 eV) between the ground and excited state. The current solution is to use an RF discharge, which is a brute force technique that is inefficient and leads to complications such contamination of the walls from ion sputtering and high gas density. A new scheme for generating a metastable beam which can achieve a cleaner, slower, and preferably more intense source would provide a substantial advance to ATTA technology. All-optical techniques have been considered, but have not yet been able to compete with the discharge source.[3] A new technique for generation of metastable krypton involves the use of a two photon transition driven by a pulsed, far-UV laser to populate the excited state which decays to the metastable state with high probability.[4]