COOLING METHODS IN ION TRAPS

In many experiments utilizing ion traps, the ions must be cooled in or der to increase the precision and accuracy of the measurements. Laser cooling is very effective when it can be applied, but it can only be u sed with a few kinds of ions, since it depends critically on the detai ls of the electronic level structure. Other methods, such as resistive cooling, active-feedback cooling, collisional cooling, radiofrequency side-band cooling, or sympathetic laser cooling, can be applied to ma ny kinds of ions. Progress in cooling of trapped ions has made possibl e improved measurements of mass ratios and atomic spectra and the obse rvation of new phenomena, such as the formation of ordered Coulomb ''c rystals'' of ions.