Optical trapping of cold atoms—new tools for atomic physics

5 Optical trapping of cold atoms—new tools for atomic physics 

The methods of trapping cold atoms, considered in Chapter 5 and the present chapter in a very brief and retrospective fashion, have become a very powerful tool in experimental physics. They have led to the development of atom optics, the observation and investigation of dilute quantum gases (Bose-Einstein condensation, atom lasers, Fermi-degenerate quantum gases, and ultracold molecules), and probably many other discoveries in the physics of ultracold atoms. These will be discussed in Chapters 7 and 8. But it would be expedient to consider at the end of this chapter a few examples of applications that lie beyond the mainstream, but are of physical interest. 

trapped radioactive atoms open up new experimental opportunities in nuclear physics. Trapped radioactive atoms can be used in experiments on the fundamental symmetries, including experiments on nuclear / -decay, atomic parity nonconservation, and the search for parity-violating and time-reversal-violating electric dipole moments. The first successful experiments on the trapping of radioactive atoms were performed with the isotope Na (Lu et al. 1994). It is expected that further activity in this direction will be concentrated on efforts to undertake meaningful measurements with trapped radioactive species. 

Recently, experiments on nuclear decay have started to use MOTs as a source of cold, well-localized atoms. The low-energy recoiling nuclei can escape from the MOT and be detected in coincidence with, 3-decays to reconstruct information about the properties of the particles coming from the nuclear reactions. An example of such an experiment is a beta- neutrino correlation measurement on laser-trapped 38mj  

An important property of the MOT is the ability to catch atoms whose optical frequencies are shifted from the laser frequency by only a few natural linewidths. This property has been applied for ultrasensitive isotope trace analysis. Chen et al. (1999) developed the technique in order to detect a counted number of atoms of the radioactive isotopes Kr and Kr, with abundances 10 and 10 relative to the stable isotope Kr. The technique was called atom trap trace analysis (ATTA). At present, only the technique of accelerator mass spectrometry (AMS) has a detection sensitivity comparable to that of ATTA. Unlike the AMS technique based on a high-power cyclotron, the ATTA technique is much simpler and does not require a special operational environment. In the experiments by Chen et al. (1999), krypton gas was injected into a DC discharge volume, where the atoms were excited to a metastable level. 2D transverse laser cooling was used to collimate the atomic beam, and the Zee-man slowing technique was used to load the atoms into the MOT. With the specific laser frequency chosen for trapping the Kr or Kr isotope, only the chosen isotope could be trapped by the MOT. The experiment was able to detect a single trapped atom of an isotope, which remained in the MOT for about a second. 

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