Physics:Atomic trap trace analysis

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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 81Kr, 85Kr, and 39Ar. 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]

References

  1. Chen, C. Y.; Li, Y. M.; Bailey, K.; O'Connor, T.P..; Young, L.; Lu. Z.T. (1999). "Ultrasensitive isotope trace analyses with a magneto-optical trap.". Science 286 (5442): 1139–1141. doi:10.1126/science.286.5442.1139. 
  2. Aprile, E.; Yoon, T.; Loose, A.; Goetzke, L.W.; Zelevinsky, T. (2013). "An atom trap trace analysis system for measuring krypton contamination in xenon dark matter detectors.". Review of Scientific Instruments 84 (9): 093105–093105–6. doi:10.1063/1.4821879. PMID 24089814. Bibcode2013RScI...84i3105A. 
  3. Kohler, M.; Daerr, H.; Sahling, P.; Sieveke, C.; Jerschabek, N.; Kalinowski, M.B.; Becker, C.; Sengstock, K. (2014). "All-optical production and trapping of metastable noble-gas atoms down to the single-atom regime.". Europhysics Letters 108 (1): 13001. doi:10.1209/0295-5075/108/13001. Bibcode2014EL....10813001K. 
  4. Dakka, M.A.; Tsiminis, G.; Glover, R.D.; Perrella, C.; Moffatt, J.; Spooner, N.A.; Moffatt, R.T.; Light, P.S. et al. (2018). "Laser-based metastable krypton generation.". Physical Review Letters 121 (9): 093201. doi:10.1103/PhysRevLett.121.093201. Bibcode2018PhRvL.121i3201D. 

Sources


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